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Reproductive performance of Little Penguins Eudyptula minor in relation to year, age, pair-bond duration, breeding date and individual quality
Abstract
We measured breeding performance of little penguins Eudyptula minor at Phillip Island, Victoria, Australia, during a 21-year period. All birds considered in this paper (n=307) were of known age (2–22 y) and sex, and most were of known, or closely-estimated, pair-bond status (1–8 mates per bird; pair-bond durations 1–13 y). Breeding dates and breeding performance varied markedly from year to year; measures of annual performance were not associated with early breeding. Measures of individual breeding performance (clutch-size, hatching success, chick masses and productivity) were related to early laying, parental age, and duration of pair-bond. Dependence of breeding performance on parental age was curvilinear, levelling off at about 8 y of age. Productivity declined significantly among birds older than 8 y; this decline was not due to events in the last year of breeding (“terminal illness”). Breeding performance increased with duration of pair-bond at least through y 5. Early breeding was significantly related to age and duration of pair-bond. Most of these relationships were stronger among males than among females, and many of them were not significant when females were considered alone. After controlling for other factors, breeding performance varied significantly among birds, but autocorrelations were low and limited to intervals of one year. Parental quality (defined for birds studied in six or more years as the individual bird term in a GLM for productivity controlling for other factors) was not correlated with lifespan or other demographic parameters, but high-quality birds were less prone to change mates and burrows than low-quality birds. We know of no previous study in which simultaneous effects of laying date, age and pair-bond duration on breeding performance were measured, while controlling for year, individual quality and terminal illness.
... Therefore, a large part of the population is made up of old birds that could significantly influence population dynamics. Furthermore, previous studies on the little penguin have shown age-dependent foraging performances (Zimmer et al. 2011), age-segregation in foraging areas (Pelletier et al. 2014) and an increase in breeding performances in the first years (Nisbet and Dann 2009). Individual foraging performance is crucial in little penguins, as they have one of the shortest known foraging ranges of seabirds (<30 km; Collins et al. 1999) and are limited by the need to return to land to feed their chicks. ...
... Using an extensive dataset of more than 450 birds monitored over a 19-yr period, we confirmed that little penguins displayed classical bell-shaped age-related changes in breeding performances Cullen 1990, Nisbet andDann 2009). Breeding success increased until age 8 then remained relatively stable before decreasing from age 16. ...
... Age-dependent patterns in breeding performances were displayed by both males and females, in contrast with Nisbet and Dann (2009), who did not find significant age changes in females. Whether this is due to a different study period, different sample sizes or other factors is unknown. ...
Reproductive performance typically improves with age, reaching a plateau at middle age and subsequently declining in older age classes (senescing individuals). Three potential non‐exclusive mechanisms can explain the improvement in reproductive performance with age: (1) selection (poor quality individuals are removed from the population with increasing age), (2) constraint (individual efficiency increases through experience) and (3) restraint (reproductive investment increases with age as the residual reproductive value decreases). While all three mechanisms received strong empirical support, few studies have aimed at teasing apart those hypotheses and understanding their underlying functioning. In little penguins (Eudyptula minor), we used a 19‐year longitudinal dataset on breeding and foraging of more than 450 individuals to investigate the effect of age on breeding success. We separated within‐ from among‐individual age‐effects using state‐of‐the‐art statistical methods (within‐subject centering and population change decomposition). We then assessed whether within‐individual changes in breeding resulted from ontogenetic changes in foraging performances, breeding phenology or access to mates and nest sites. Fidelity and assortative pairing explained the high correlation in male and female ages within a pair. Breeding performances followed a typical bell‐shaped curve with performance increasing up to 8 years‐old, before reaching a plateau and subsequently declining after age 16. Both selection and within‐individual processes occurred, although within‐individual changes dominated differences in age‐dependent breeding success. The selective appearance had almost no effect (apart from ages 2 to 3), and selective disappearance mostly affected changes at old ages (above 16), although they were also responsible for the slight increase in reproductive performances from ages 5 to 8. Focusing on within‐individual changes, birds exhibited higher performances at middle ages, with birds foraging better, laying earlier and changing partner and nest less often. Their reproductive investment did not vary with age for females and slightly decreased for males. This supports the constraint hypothesis but not the restraint one. Finally, the increase in breeding performances at young ages was explained by the age‐related increase in foraging performances during chick‐rearing and advancement of laying. In contrast, reproductive senescence was defined by a general decrease in bird performances.
... Differences in life-history strategies have also been observed among populations of the same species as a likely phenotypic response to a given set of environmental conditions or genetically structured differentiation among distant populations (Lahann & Dausmann, 2011;Schultner et al., 2013). Within populations, intrinsic constraints such as an individual's age (a proxy for experience or survival prospects, Froy et al., 2013) may influence the frequency and success of reproductive events over time, by altering the allocation of resources to life-history functions (Froy et al., 2013;Nisbet & Dann, 2009;Ramírez et al., 2015;Reed et al., 2008;Zimmer et al., 2011). ...
... The age of most birds was calculated in the year an individual was marked with a transponderat fledging. For the few individual penguins that were marked as an adult, we added three years to their calculated age to allow for the time taken for a fledgling to become sexually mature and return to the colony as a breeding adult (Nisbet & Dann, 2009). ...
... Throughout their lifetime, individuals are exposed to varying pressures or constraints (i.e., "boundary conditions"; Stearns, 1992), and they can attempt to maximize their lifetime fitness by adapting their resource allocation strategies (Nichols et al., 1976). As individuals age and their residual reproductive value decreases and their experience increases, resource allocation to reproduction is expected to rise, sometimes at the expenses of their own survival and, hence, of their future reproductive attempts (Froy et al., 2013;Nisbet & Dann, 2009;Ramírez et al., 2015). Therefore, older seabirds are more likely to try to increase their breeding output by starting reproduction earlier in the year or by engaging in additional breeding attempts within a year (Limmer & Becker, 2010). ...
The extrinsic and intrinsic factors affecting differing reproductive strategies among populations are central to understanding population and evolutionary ecology. To evaluate whether individual reproductive strategies responded to annual patterns in marine productivity and age‐related processes in a seabird we used a long term (2003–2013), a continuous dataset on nest occupancy and attendance at the colony by little penguins (Eudyptula minor) at Phillip Island (Victoria, Australia). We found that concurrent with a secondary annual peak of marine productivity, a secondary peak in colony attendance and nest occupancy was observed in Autumn (out of the regular breeding season in spring/summer) with individuals showing mating‐like behavior. Individuals attending this autumn peak averaged 2.5 years older than those individuals that exclusively bred during spring/summer. Rather than being a naïve response by younger and inexperienced birds misreading environmental cues, our data indicate that the autumn peak attendance is an earlier attempt to breed by older and more experienced penguins. Therefore, we provide strong support for the fundamental prediction of the life‐history theory of increasing investment in reproduction with age to maximize lifetime fitness as future survival prospects diminish and experience increases.
... Suitable breeding habitat is typically characterised as sandy beaches, bays, or creek mouths within areas of sheltered peripheral coastline associated with rocky headlands or points Challies and Burleigh 2004;Stevenson and Woehler 2007;Allen et al. 2011). Primarily a burrowing bird, nesting adults will excavate cavities in sandy soil Nisbet and Dann 2009), dunes (Braidwood et al. 2011), pasture (Allen et al. 2011) and fine debris from coastal slips (Challies and Burleigh 2004). Where the substrate is unsuitable for burrowing, rocky crevices, driftwood piles, dense undergrowth and the exposed root systems of coastal vegetation are readily occupied (Challies and Burleigh 2004;Heber et al. 2008;Nisbet and Dann 2009;Braidwood et al. 2011). ...
... Primarily a burrowing bird, nesting adults will excavate cavities in sandy soil Nisbet and Dann 2009), dunes (Braidwood et al. 2011), pasture (Allen et al. 2011) and fine debris from coastal slips (Challies and Burleigh 2004). Where the substrate is unsuitable for burrowing, rocky crevices, driftwood piles, dense undergrowth and the exposed root systems of coastal vegetation are readily occupied (Challies and Burleigh 2004;Heber et al. 2008;Nisbet and Dann 2009;Braidwood et al. 2011). Breeding pairs are frequently recorded utilising sheltered spaces beneath buildings (Heber et al. 2008) and artificial structures including water tanks (Braidwood et al. 2011). ...
... Breeding pairs are frequently recorded utilising sheltered spaces beneath buildings (Heber et al. 2008) and artificial structures including water tanks (Braidwood et al. 2011). Artificial burrows (purpose-built nest boxes, PBNBs) are used successfully throughout the breeding range Heber et al. 2008;Nisbet and Dann 2009;Braidwood et al. 2011). ...
The identification and subsequent protection of suitable breeding habitat for little penguins (Eudyptula minor) is restricted by data deficiency across large stretches of the species range. For example, presence/absence data is lacking for much of the Canterbury coast, mainland New Zealand. In October 2019, a Protected Species Detection Dog was used to conduct the first comprehensive survey for E. minor along the greater Kaikōura coastline. The principal objectives were to locate and map the distribution of sites utilised by E. minor between Waipapa Bay and the Conway River, characterise areas of suitable breeding habitat and identify ‘little blue’ and ‘white-flippered’ morphotypes. Eudyptula minor were located within just 0.7% of a coastal stretch measuring c. 75 km. A single breeding colony was located in severely fragmented habitat on the southern face of the Kaikōura Peninsula, South Bay. The Detection Dog gave positive indications at six further isolated sites in sheltered bays, including two active nests on the northern faces of Spy Glass Point (Piripaua) and the Kaikōura Peninsula. We highlight the importance of the breeding colony at South Bay, Kaikōura, and recommend the protection of existing habitat as a priority for the survival of E. minor along the greater Kaikōura coastline.
... Once hatched, the chicks are guarded and brooded by both parents on alternate days, with the guard stage lasting for 2 to 3 weeks. During the post-guard stage, when the chicks are older and more capable of thermoregulating, both parents forage at sea during the day, returning after dark to feed their chicks (Nisbet & Dann 2009). ...
... Such changes have been reported to cause increased foraging effort in little blue penguins and disrupt their regular breeding, in turn affecting the entire breeding population in an area (Dann et al. 2000;Numata et al. 2004;Robinson et al. 2005;Ropert-Coudert et al. 2009;Chiaradia et al. 2010). Similarly, variations in the availability of food have resulted in delays to the start of the breeding period, reduced likelihood that a second clutch will be produced, and increased chick mortality (Dann et al. 2000;Nisbet & Dann 2009;Chiaradia et al. 2010). Reduction in food availability can also lead to poor adult and chick body condition, resulting in reduced chick immunity and longer fledging periods (Dann et al. 2000;Chiaradia et al. 2010). ...
... Foraging behaviour during incubation and chick rearing (including diving behaviour, foraging range and trip length) impacts the reproductive success of little blue penguins (Dann et al. 2000;Nisbet & Dann 2009;Chiaradia et al. 2010). Poupart et al. (2017) undertook foraging location research on Motuara Island little blue penguins contemporaneously with this study in 2014, and again in 2015. ...
... If both parents are extremely poor breeders, the expected number of fledglings will be only 15% of a nest with two extremely good breeders (electronic supplementary material, figure S2). This is very similar to the maximum difference in reproduction of 15.2% caused by individual heterogeneity in a study of the little penguin (Eudyptes minor [32]). In addition, by including these individual effects, we control for autocorrelation between repeated measurements from the same individuals. ...
... Contrary to our findings, there is evidence that, in some species, breeding performance improves with the duration of pair bond. This has been reported in northern fulmars (Fulmarus glacialis [38]), short-tailed shearwaters (Puffinus tenuirostris [39]), barnacle geese (Branta leucopsis [40], Cassin's auklets (Ptchoramphus aleuticus [41]), barn swallows (Hirundo rustica [21]) and little penguins [32]. ...
... In accordance with our findings, longer pair bonds made a mate change less likely in black-legged kittiwakes [3] and little penguins [32]. By contrast, pair bond length had no effect on divorce probability in white-chinned petrels [19] and in oystercatchers (Haematopus ostralegus [20]). ...
In a monogamous species two partners contribute to the breeding process.We study pair formation as well as the effect of pair bond length and age on breeding performance, incorporating individual heterogeneity, based on a high-quality dataset of a long-lived seabird, the common tern (Sterna hirundo). To handle missing information and model the complicated processes driving reproduction, we use a hierarchical Bayesian model of the steps that lead to the number of fledglings, including processes at the individual and the pair level. The results show that the age of both partners is important for reproductive performance, with similar patterns for both sexes and individual heterogeneity in reproductive performance, but pair bond length is not. The terns are more likely to choose a former partner independent of the previous breeding outcome with that partner, which suggests a tendency to retain the partner chosen at the beginning of the breeding career. © 2017 The Author(s) Published by the Royal Society. All rights reserved.
... Overall breeding success is defined as the number of chicks that fledge relative to the number of eggs laid. Factors that have been found to lead to high hatching, fledging or breeding success for pairs or individual birds in Australian blue penguin colonies include better body condition (assessed as mass divided by flipper length) at incubation (Robinson et al. 2005), later relative lay dates (Nisbet & Dann 2009), more sheltered nesting habitat (Knight & Rogers 2004), younger bird age, and longer pair bond length (Nisbet & Dann 2009). When comparing breeding success between colonies, shallow ocean bathymetry (Chiaradia et al. 2007) and lower latitude (Fortescue 1999) have been identified as factors that can lead to increased hatching, fledging or breeding success. ...
... Overall breeding success is defined as the number of chicks that fledge relative to the number of eggs laid. Factors that have been found to lead to high hatching, fledging or breeding success for pairs or individual birds in Australian blue penguin colonies include better body condition (assessed as mass divided by flipper length) at incubation (Robinson et al. 2005), later relative lay dates (Nisbet & Dann 2009), more sheltered nesting habitat (Knight & Rogers 2004), younger bird age, and longer pair bond length (Nisbet & Dann 2009). When comparing breeding success between colonies, shallow ocean bathymetry (Chiaradia et al. 2007) and lower latitude (Fortescue 1999) have been identified as factors that can lead to increased hatching, fledging or breeding success. ...
... Higher hatching and overall breeding success at Flea Bay were significantly associated with a later relative lay date, the second most important predictor of breeding success. A later relative lay date was also found to explain higher breeding productivity by individual blue penguins (chicks fledged per breeding attempt) in Australia where breeding productivity increased until around 10 days after the annual average lay date and then began to decrease (Nisbet & Dann 2009). In contrast, the prevailing trend in seabirds is for an earlier relative lay date leading to increased breeding success (Pezzo et al. 2001; Paredes et al. 2002). ...
The little blue penguin (Eudyptula minor) is in decline throughout much of its range in New Zealand
and Australia, largely due to introduced predators, human disturbance and roadkill mortalities. The white flippered penguin is a unique morphological variant of the blue penguin, which is traditionally given subspecific status (Eudyptula minor albosignata), and is found only on Banks Peninsula and Motunau Island in Canterbury, New Zealand. We monitored a varying number of nest boxes from 1996 to 2009. Overall breeding success was 64% over 13 years of monitoring, with a hatching success rate of 75% and a fledging success rate of 85%. We used a set of generalised linear mixed models and model selection to examine the relative influence of various explanatory variables on hatching, fledging and overall breeding success. Breeding success in nest boxes significantly increased with shorter average pair bond length, longer guard period and later relative lay date. Guard period length was the best predictor of breeding success, followed by relative lay date and average pair bond length. Hatching success also increased with later relative lay date but fledging success was not influenced by any of the explanatory variables measured.
... Further, there is evidence of individual differences in foraging ability, such that some individuals seem to be better equipped to manage periods of poor food availability than others [16]. While the mechanisms are not clear, little penguins that breed early are more likely to hatch their eggs successfully and produce heavier chicks [22]. Earlier laying is also more likely to result in relaying and, consequently, more clutches per season [17]. ...
... Earlier laying is also more likely to result in relaying and, consequently, more clutches per season [17]. Although this suggests there should be selection for early breeding, the spread of laying dates can [17,22,23]. These variations in parent's ability to prepare for breeding support the hypothesis that there are some carry-over effects from the inter-breeding season to breeding. ...
... It may be that good quality individuals are able to efficiently require resources when they are needed and therefore do not need to acquire high levels of reserves in winter in order to breed early. Or perhaps it is differences in experience, as demonstrated in breeding and foraging efficiency [22,50,51] that result in some individuals using winter reserves to improve their breeding potential, whereas others are less equipped to capitalize on this carryover benefit. The differences only observed in 2005 illustrated that an exceptional good winter could influence subsequent breeding. ...
1. Summary Using body mass and breeding data of individual penguins collected continuously over 7 years (2002–2008), we examined carry-over effects of winter body mass on timing of laying and breeding success in a resident seabird, the little penguin (Eudyptula minor). The austral winter month of July consistently had the lowest rate of colony attendance, which confirmed our expectation that penguins work hard to find resources at this time between breeding seasons. Contrary to our expectation, body mass in winter (July) was equal or higher than in the period before ('moult-recovery') and after ('pre-breeding') in 5 of 7 years for males and in all 7 years for females. We provided evidence of a carry-over effect of body mass from winter to breeding; females and males with higher body mass in winter were more likely to breed early and males with higher body mass in winter were likely to breed successfully. Sex differences might relate to sex-specific breeding tasks, where females may use their winter reserves to invest in egg-laying, whereas males use their winter reserves to sustain the longer fasts ashore during courtship. Our findings suggest that resident seabirds like little penguins can also benefit from a carry-over effect of winter body mass on subsequent breeding.
... Breeding in little penguins at Phillip Island usually occurs in the Austral spring and summer between August and February (Nisbet and Dann 2009). Little penguins incubate 2 eggs of equal size for about 35 days (Kemp and Dann 2001) and return to feed their chicks for another 55 days or more before the chicks fledge Cullen 1981, Chiaradia andNisbet 2006). ...
... We did not consider any models with an interaction term in more than 1 of w, p, or f to minimize over-parameterization, but the interaction term allowed residency patterns to vary independently between years and nest types. All models considered w, p, and f varying with time because we expected colony attendance patterns to vary among years for little penguins (Nisbet and Dann 2009). We considered models with and without sex because sex also is likely to influence attendance patterns (Nisbet and Dann 2009). ...
... All models considered w, p, and f varying with time because we expected colony attendance patterns to vary among years for little penguins (Nisbet and Dann 2009). We considered models with and without sex because sex also is likely to influence attendance patterns (Nisbet and Dann 2009). Second, we considered the same set of models again but with study area replacing nest type as a factor. ...
The persistence of many cavity-nesting animals is threatened by habitat modification and a shortage of suitable breeding sites. Consequently, provision of alternative breeding sites is a frequently applied short- to medium-term conservation action. However, the effectiveness of provisioning for breeding success and persistence of breeding animals is rarely considered and could lead populations into an ecological trap. We evaluated the effectiveness of providing nest boxes for little penguins (Eudyptula minor) compared with natural nests over 25 years. We assessed nest-box adoption and occupancy rates, compared breeding success (i.e., hatching and fledging success) and indices of productivity (i.e., observed brood size, total fledged chick mass, and the number of clutch initiations) with nest survival models and log-linear mixed effects models, and compared long-term residency patterns with Link–Barker mark-recapture models between artificial and natural nests. Little penguins readily adopted nest boxes and breeding attempts were recorded in about 92% of nest boxes installed for 7 or more years. Breeding productivity from 6,081 monitored clutches varied by year and was similar across nest types in most years, but in poor breeding seasons nest boxes performed better. Survival rates to hatching and fledging averaged 7.6% and 8.6% greater in nest boxes, respectively. Similarly, the average total observed mass of chicks produced per clutch was 11% heavier in nest boxes. Annual site fidelity of 2,331 breeding penguins was similar in areas with nest boxes and areas with natural burrows, despite an average of 35% of natural burrows collapsing each year. Nest-box provisioning for little penguins overcomes local nest-site limitation, improves breeding success, and can result in local population increases, so is not indicative of an ecological trap. However, a self-sustaining local population in the long term will require management strategies that address the underlying processes inhibiting population recovery and assist the transition from artificial nest sites back to natural nest sites. © 2014 The Wildlife Society.
... Once hatched, the chicks are guarded and brooded by both parents on alternate days, with guard stage lasting for 2-3 weeks. During the post-guard stage, when the chicks are older and more capable of thermoregulating, both parents forage at sea during the day, returning after dark to feed their chicks (Nisbet and Dann 2009). ...
... These changes in prey were found to cause LBPs to increase foraging effort and disrupt their regular breeding, in turn affecting the entire breeding population (Dann et al. 2000;Numata et al. 2004;Robinson et al. 2005;Ropert-Coudert et al. 2009;Chiaradia et al. 2010). Similarly, variations in the availability of food have resulted in delays to the start of the breeding period, reduced likelihood that a second clutch will be produced, and increased chick mortality (Dann et al. 2000;Nisbet and Dann 2009;Chiaradia et al. 2010). Changes in food availability also lead to poor adult and chick body condition, resulting in reduced chick immunity and longer fledging periods (Dann et al. 2000;Chiaradia et al. 2010). ...
The breeding success, foraging strategies and abundance of penguin species are thought to vary according
to the quality of near-shore marine environments. Little blue penguins (LBP), Eudyptula minor, in particular,
are considered a candidate species for assessing near-shore marine productivity and integrity due to their limited foraging ranges and reliance on local resources, particularly during breeding. However, to assess their ability to be nearshore ecosystem indicators an understanding of what their “normal” dive patterns and population parameters from across New Zealand are needed. This research investigates diving behaviours and feather stable isotope values (as indicators of diet) of LBPs from southern (Pearl Island, Stewart Island/Rakiura, Nov. 2011) and central (Adele Island, Abel Tasman, Nov. 2012) New Zealand (NZ), two areas not previously studied, and compares them with LBPs from other areas of NZ. The diving behaviours of LBPs across NZ, are highly variable, not obviously linked with local geography and bathometry. These results and the NZ wide comparison indicates that LBPs are environmentally adaptable, which may make them difficult to use as ecosystem indicators across sites. However, with increasing knowledge of diving behaviours and population parameters of LBPs within a region, they are likely to be indicators of local changing marine environment.
... Several studies have shown that individuals optimize the onset of breeding and breeding performance through repeated breeding attempts with the same partner (Bradley et al. 1995;van de Pol et al. 2006;Naves et al. 2007;Nisbet andDann 2009, but see McDonald et al. 2004). In our study, however, neither the onset of breeding nor number of fledglings were influenced by pair-bond duration. ...
... This, combined with the fact that perennial pairs and newly formed pairs of 2 experienced breeders did not differ in these 2 variables, suggests that hair-crested drongos do not benefit from mate retention in terms of breeding performance. It is interesting to note that all previous studies that reported an improved breeding performance, when pair-bonds lasted over extended periods, occurred in long-lived birds (Bradley et al. 1995;Black 2001;van de Pol et al. 2006;Naves et al. 2007;Nisbet and Dann 2009). In contrast, the average length of pair-bond duration in the haircrested drongo was less than 3 years, which is much shorter than in previous studies. ...
Individuals that retain their former partners often perform better than conspecifics that switch partners. This may be due
to high-quality individuals being more faithful to their partners and more productive. Investigations of the fitness benefits
of mate retention that also control for potential confounding effects of individuals are scarce. We studied the influence
of mate retention and breeding experience on breeding performance of the hair-crested drongo (Dicrurus hottentottus) by carrying out both cross-sectional and longitudinal analyses. Pairs with longer pair-bond duration did not fledge more
young or fledglings of better body condition nor did they produce more or better fledglings than newly formed pairs consisting
of at least 1 experienced breeder, that is, individuals that had bred before. Individuals produced fewer fledglings when they
were paired with an inexperienced breeder, especially when females were paired with inexperienced males. Although clutch size
was not affected by mate retention or breeding experience, pairs consisting of inexperienced breeder(s) had a relatively higher
predation rate of eggs and/or nestlings because they may be less effective in nest defense. The onset of breeding was advanced
in the year following mate retention, but not in the second year thereafter, when pairs still remained together. Furthermore,
only the breeding experience of the male determined the onset of breeding: Pairs consisting of inexperienced males bred later
in the season. Our results suggest that breeding experience, and particularly the breeding experience of the male, but not
mate retention, is important in determining the breeding performance of hair-crested drongos.
... Troubridge Island populations however -two supposedly stable colonies -showed the lowest breeding success. Long-term studies on Phillip and Bowen Islands showed that annual variation in breeding success is common in little penguins (Reilly & Cullen 1981;Fortescue 1999;Nisbet & Dann 2009). For example, annual breeding success on Philip Island greatly varied from 0.08 to 1.38 fledglings per pair (Reilly & Cullen 1981;Nisbet & Dann 2009). ...
... Long-term studies on Phillip and Bowen Islands showed that annual variation in breeding success is common in little penguins (Reilly & Cullen 1981;Fortescue 1999;Nisbet & Dann 2009). For example, annual breeding success on Philip Island greatly varied from 0.08 to 1.38 fledglings per pair (Reilly & Cullen 1981;Nisbet & Dann 2009). But comparing with breeding data from previous years, low breeding success at Antechamber Bay and Troubridge Island does not seem to be the result of inter-annual variation (Table 6). ...
... This period overlapped with the latter stages of the 2012 breeding season and the early stages of the 2013 breeding season of penguins and gulls, and the 2012 breeding season of shearwaters. The penguin breeding season occurred from late August to December with egg laying peaking during September-October and incubation for about a further 35 days (Marchant & Higgins 1990;Nisbet & Dann 2009). During the study, egg laying peaked for gulls from September to mid-October (with incubation for about a further 24 days; Wheeler & Watson 1963, Higgins & Davies 1996, although the peak of egg laying in most years occurs in September (L. ...
... The shearwater breeding season occurred from late November to January with egg laying peaking during 25-30 November and incubation for about a further 53 days (Serventy et al. 1971;Marchant & Higgins 1990;Carey 2011a). The peak of egg laying in shearwaters and gulls is more synchronised than that of penguins (Nisbet & Dann 2009), so here we report the proportion of penguin nests with eggs for each month as a more accurate measure of penguins' peak egg laying period. The penguin and gull breeding seasons occurred from late August to December with incubation during September and October, and the shearwater breeding season from late November to February with incubation during December and January. ...
Egg predation is a major cause of reproductive failure among birds, and can compromise the viability of affected populations. Some egg predators aggregate near colonially breeding birds to exploit the seasonal increase of prey resources. We investigated spatial and temporal variations in the abundance of an egg predator (little raven Corvus mellori; Corvidae) to identify whether ravens aggregate spatially or temporally to coincide with any of three potential prey species: burrow-nesting little penguin (Eudyptula minor; Spheniscidae), short-tailed shearwater (Ardenna tenuirostris; Procellariidae), and surface-nesting silver gull (Chroicocephalus novaehollandiae; Laridae). We derived spatially explicit density estimates of little ravens using distance sampling along line transects throughout a calendar year, which encompassed little penguin, short-tailed shearwater and silver gull breeding and non-breeding seasons. High raven abundance coincided temporally with penguin and gull egg laying periods but not with that of shearwaters. The spatial distribution of raven density corresponded with the little penguin colony but not with shearwater or gull colonies. Thus, the presence of little penguin eggs in burrows correlated strongly with little raven activity, and this implies that little ravens may have learnt to exploit the plentiful subsurface food resource of little penguin eggs. Corvid management may be required to maintain the viability of this socially and economically important penguin colony.
... Authors suggest that male attractiveness influenced egg steroid levels as egg testosterone levels were higher when females were exposed to attractive males (Gil et al., 1999;Gil et al., 2004;Kingma et al., 2009), and this could influence chicks' development (Groothuis et al., 2005). Once a pair has formed, pair-bond duration impacts breeding success directly (Black, 1996;Hall, 1999;Nisbet and Dann, 2009). ...
... In particular, clutch size, hatching success and chick weights are directly linked to parental pair-bond duration of little penguins, Eudyptula minor (Nisbet and Dann, 2009). Besides this relationship duration, behavioural compatibility between mates influences offspring indirectly, as the more the traits of the two mates correspond, the better their activities, including nest attendance, are coordinated, and so the greater their breeding success (Coulson, 1966;Coulson, 1972;Spoon et al., 2006). ...
This thesis explored non-genetic maternal influences in a precocial bird, the Japanese quail Coturnix c. japonica. A first approach investigated the influence of an intrinsic factor on the behaviour of a laying female, its eggs' characteristics and its offspring's development. Our results demonstrate that intrinsic characteristics of egg laying behaviour influence females' emotivity. Eggs laid by females that present a stable laying profile (i.e. ovoposition at the same time each day) differed from eggs laid by females that present a delayed laying profile (i.e. oviposition later each day). Offspring of females delayed laying profile showed higher emotivity in novel situations and social isolation. Moreover, eggs presented specific characteristics within each of both egg laying profiles. A second approach focused on the biotic environment. For a female, the mating partner is a particular congener. When mates could develop a pair bond (by continuous pairing), their offspring were more emotive and less social compared to chicks whose parents were not continuously paired and thus did not develop a pair bond. In a final approach and for the first time in a precocial bird, interactions between prenatal and postnatal maternal influences were explored. Chicks that were prenatally stressed showed lower emotivity in novel situations and social isolation when they are mothered after hatching compared to non-mothered, prenatally stressed chicks. Overall, our work improves the knowledge about maternal influence factors of variation, their mechanisms and consequences, allowing a better understanding of individuals' phenotypic variability and populations' evolution.
... Egg mass (and size) and consequently total clutch mass in birds are closely linked to female body mass (reviewed in Christians 2002) and a determinant of hatchling size (reviewed in Krist 2011), which has also been shown in penguins (Reid and Boersma 1990). Finally, CID in many bird species, including penguins (Moreno et al. 1997(Moreno et al. , 1998, is constrained by the females' ability to form eggs, with higher quality (often more experienced) females being able to lay earlier and consequently having higher breeding performances (Perrins 1973;Nisbet and Dann 2009;Polito et al. 2010). ...
... As female body mass, clutch mass and CID have been reliable indicators of female quality in other birds, including penguins (e.g. Perrins 1973;Nisbet and Dann 2009;Polito et al. 2010), it appears unlikely that none of them would signal female quality in southern rockhopper penguins. On the other hand, a female's antioxidant capacities and thus ability to deposit biliverdin into her eggs might not be reflected by its body mass but might necessitate the measurement of plasma antioxidants in the female's blood (Morales et al. 2008). ...
Eggshell blue-green colouration (BGC) is caused by the pigment biliverdin which has antioxidant capacities. Eggshell BGC has therefore been interpreted as being costly for the female and therefore a signal of female quality (‘sexual signalling hypothesis’). Southern rockhopper penguins Eudyptes chrysocome exhibit both a reversed hatching asynchrony and a brood reduction strategy. First-laid (A-)eggs are smaller and hatch on average 1 day after second-laid (B-)eggs, with B-eggs usually producing the only surviving chick. According to the sexual signalling hypothesis, we predicted a positive relationship between BGC and both female body mass and egg mass, and consequently within clutches a stronger BGC in B-eggs than A-eggs. Furthermore, we expected a negative relationship between BGC and clutch initiation date. Contrasting these expectations, we found no effect of female body mass or egg mass on BGC, and BGC in A-eggs increased with clutch initiation date, while there was no effect in B-eggs. Within clutches, A-eggshells were more intensely blue-green coloured than B-eggshells. Concluding, our results appear to contradict the sexual signalling hypothesis. We, however, did not measure pigment concentrations and solely relied on BGC from eggshell photospectrometry, assuming that biliverdin concentrations were positively correlated with BGC. We therefore caution that before precluding the sexual signalling hypothesis, future studies that include measurements of eggshell pigment concentrations in addition to BGC are necessary. Altogether, a better understanding of the biological meaning of biliverdin, its biochemical synthesis and antioxidative function in the avian body is urgently needed.
... Aptenodytes penguins, frigatebirds and some cormorants; see review in Bried and Jouventin 2002), fidelity to mates and nest-sites, that is breeding with the same mate and on the same territory, respectively, from one breeding season to the next, in seabirds are most likely to occur after a successful breeding attempt (Bradley et al. 1990;Pyle et al. 2001). Familiarity with a mate may improve breeding success through better coordination of incubation shifts and chick-feeding schedules of members of pairs (Ens et al. 1996;Nisbet and Dann 2009). Nest-site fidelity in turn, may be advantageous by allowing greater familiarity with local food resources (depending on the spatial scale of variability in resources), potential mates, neighbours, competitors, predators and shelter from adverse weather (Hinde 1956;Greenwood and Harvey 1982;Harwood et al. 2003). ...
... This agrees with the findings of Fleet (1974) on Kure Atoll, and substantiates our finding that pair-bond disruption and subsequent breeding with a new mate for the first time is costly in Red-tailed Tropicbirds. Unfamiliarity with a new mate probably reduces the fine-tuning of breeding behaviour (Ens et al. 1996;Nisbet and Dann 2009), which decreases the probability of rearing a chick successfully. However, individual age should ideally be taken into account when analysing the relationship between mate-fidelity and breeding success, as older birds are likely to be more successful breeders than younger, less-experienced breeders (Curio 1983). ...
Disruption of pair-bonds and switching nest-site are associated with breeding failure in many seabirds. Both strategies can prevent repetition of poor performance with a low-quality mate or at a poor-quality nesting site. In the Red-tailed Tropicbird (Phaethon rubricauda), the relationship between mate-fidelity, nest-site fidelity and reproductive performance is poorly understood. We therefore examined this relationship in Red-tailed Tropicbirds, using data collected on Christmas Island in the Indian Ocean from 1984 to 1986, corresponding to three successive breeding seasons. Birds showed strong between-season mate-fidelity, despite previous breeding failure, and subsequent breeding success in birds faithful to their mate was significantly higher than in pairs that bred together for the first time, indicating that mate-fidelity may outweigh the costs of disruption of pair-bonds. Although switching of nest-site was more likely to occur after previous breeding failure, it did not increase subsequent breeding success, indicating that nest-site switching may not be advantageous in Red-tailed Tropicbirds on Christmas Island. Although effects of age, dispersal rates to inaccessible parts of the island and adult survival were not examined in this study, our results provide a valuable basis for the evaluation of population dynamics of Red-tailed Tropicbirds on Christmas Island.
... The researchers suggest that male attractiveness influenced egg steroid levels as egg testosterone levels were higher when females were exposed to attractive males (Gil et al., 1999;Gil et al., 2004;Kingma et al., 2009), and this could influence chick development (Groothuis et al., 2005). Once a pair has formed, pairbond duration impacts breeding success directly (Black, 1996;Hall, 1999;Nisbet and Dann, 2009). In particular, clutch size, hatching success and chick weight are directly linked to parental pair-bond duration of little penguins, Eudyptula minor (Nisbet and Dann, 2009). ...
... Once a pair has formed, pairbond duration impacts breeding success directly (Black, 1996;Hall, 1999;Nisbet and Dann, 2009). In particular, clutch size, hatching success and chick weight are directly linked to parental pair-bond duration of little penguins, Eudyptula minor (Nisbet and Dann, 2009). Besides this relationship duration, behavioural compatibility between mates influences offspring indirectly, as the more the traits Long-life partners or sex friends? ...
Previous investigations reported that some traits of parental relationships, including pair-bond duration or mate behavioural compatibility, influence subsequent offspring fitness by acting on their behaviour, growth and thus their early survival. We hypothesized that the development of a pair-bond between sexual partners would have a prenatal influence. This study investigated the impact of two pairing managements on the egg characteristics and development of offspring of Japanese quail (Coturnix c. japonica). Thirty males and 30 females were paired either continuously (C) (mates together all the time) or non-continuously (NC) (pairs met only three times a week for five minutes). Separation-reunion tests evaluated parental pair bond. Egg yolk testosterone and androstenedione levels were evaluated, and the somatic and behavioural development of C and NC chicks was assessed. Our results revealed that members of C pairs were attached to their mates and, although no significant differences in androgen levels could be evidenced between egg sets, a higher proportion of C pairs' eggs were fertilized and their chicks appeared less emotive and more social. Our results revealed that parental relationship can modulate the behavioural development of their offspring, probably via non-genetic effects, and this could play a major role in the emergence of inter-individual variability.
... Boobies that were together for longer: (i) established their clutches earlier in the season, (ii) hatched more of their eggs, and (iii) produced more fledglings, independent of their age and reproductive experience. This suite of benefits is consistent with descriptive observations of other avian species suggesting that reproductive output improves over the natural pair bond as a result of a progressive advance in the onset of breeding [24,27,28]. Bringing egg laying forward can greatly increase egg survival [51,52], which in turn can increase reproductive success. ...
... In our cross-sectional data, the greatest improvement in onset of breeding and reproductive output occurred on the first remating (figures 1 and 2). Similarly, in other birds reproductive performance strongly improves on the first remating, then tends to stabilize, although in exceptional cases it declines towards the end of long bonds [26][27][28]. The steep reproductive improvement on the booby's first remating could be owing to familiarity with the mate's traits and behaviour acquired during their first breeding event together. ...
Prolonged pair bonds have the potential to improve reproductive performance of socially monogamous animals by increasing pair familiarity and enhancing coordination and cooperation between pair members. However, this has proved very difficult to test robustly because of important confounds such as age and reproductive experience. Here, we address limitations of previous studies and provide a rigorous test of the mate familiarity effect in the socially monogamous blue-footed booby, Sula nebouxii, a long-lived marine bird with a high divorce rate. Taking advantage of a natural disassociation between age and pair bond duration in this species, and applying a novel analytical approach to a 24 year database, we found that those pairs which have been together for longer establish their clutches five weeks earlier in the season, hatch more of their eggs and produce 35% more fledglings, regardless of age and reproductive experience. Our results demonstrate that pair bond duration increases individual fitness and further suggest that synergistic effects between a male and female's behaviour are likely to be involved in generating a mate familiarity effect. These findings help to explain the age- and experience-independent benefits of remating and their role in life-history evolution.
... Using a standardized template for data collection, we organized the following information from each study: whether the study was observational or experimental, species examined, number of years the researcher(s) had studied the population, factors that the researcher (s) considered, and which hypotheses were supported by their results (Table S1; section 'Discussion'). We also used several longevity databases (Australian Bird Study Association Data; Cornell Lab of Ornithology Birds of North America; Euring; Max Planck Institute for Demographic Research) and published studies (Zann 1996;Møller 2006;Richardson et al. 2007;Nisbet & Dann 2009;Schmoll et al. 2009;Wasser & Sherman 2010) to obtain information on the maximum recorded longevity in the wild per species. This enabled us to assess the potential role of different lifehistory strategies in the patterns of hypotheses proposed for ARIRP (section 'Discussion'). ...
... Mate fidelity is understood as an individual repetitively mating with an individual across breeding seasons or years (Bradley et al. 1990;Nisbet & Dann 2009). There are many potential benefits to remating Ethology 120 (2014) 1-16 © 2014 Blackwell Verlag GmbH with the same individual, which may differ across mating systems, such as coordination of parental duties (Ens et al. 1993), decreased mate-search effort, and earlier breeding times. ...
Improvement in reproductive performance with age, up to the point of senescence, is a predominant pattern among vertebrates. Predictions from life-history theory provide a powerful framework for understanding the evolutionary basis of these patterns. However, based on the growing number of publications on this topic, there is increased interest in understanding the proximate causes of age-related improvements in reproductive performance (ARIRP). A formal conceptual framework through which factors related to ARIRP can be examined is lacking. Here, we establish hypotheses with testable predictions for social and ecological factors, including resource quality, mate fidelity, site fidelity, prior breeding experience, and changes in ability to attract mates. We use this conceptual framework to review 55 empirical studies published (between 1900 through 2013) on avian species as birds have the greatest representation in empirical studies of ARIRP. Our synthesis revealed that tests of the breeding experience hypothesis are most prevalent in the literature, whereas tests of the site fidelity hypothesis are least prevalent. Overall, the role of increased mate attraction with age seems to be an important predictor of ARIRP, whereas changes in resource quality with age show the least support among published studies. Because many studies suffered from small sample sizes and did not control for confounding variables, we suggest experimental methodologies for teasing apart hypotheses in empirical investigations and offer statistical approaches for longitudinal datasets. From an ultimate perspective, we also highlight the role of life-history variation, in shaping within-individual improvements. Future work should employ a standardized framework to study patterns of ARIRP, as set forward here, to allow for more quantitative comparison of results across studies.
... For instance, in monogamous birds, it is a common observation that pairs improve their breeding success across joint breeding attempts (e.g. [66][67][68]; a form of collective learning by our definition). In theory, this improvement could arise if individuals progressively learn to better account for their partner's state to adjust their parental behaviour [64]. ...
Learning is ubiquitous in animals: individuals can use their experience to fine-tune behaviour and thus to better adapt to the environment during their lifetime. Observations have accumulated that, at the collective level, groups can also use their experience to improve collective performance. Yet, despite apparent simplicity, the links between individual learning capacities and a collective's performance can be extremely complex. Here we propose a centralized and broadly applicable framework to begin classifying this complexity. Focusing principally on groups with stable composition, we first identify three distinct ways through which groups can improve their collective performance when repeating a task: each member learning to better solve the task on its own, members learning about each other to better respond to one another and members learning to improve their complementarity. We show through selected empirical examples, simulations and theoretical treatments that these three categories identify distinct mechanisms with distinct consequences and predictions. These mechanisms extend well beyond current social learning and collective decision-making theories in explaining collective learning. Finally, our approach, definitions and categories help generate new empirical and theoretical research avenues, including charting the expected distribution of collective learning capacities across taxa and its links to social stability and evolution.
This article is part of a discussion meeting issue ‘Collective behaviour through time’.
... Aubry et al., 2009;Berman et al., 2009;Bouwhuis et al., 2009;Froy et al., 2017). Within-individual improvements in early adulthood are likely the result of individuals reaching physiological maturity at different rates (Ainley, 1978) or acquiring or becoming more proficient at required skills necessary to reproduce successfully (Balbontín et al., 2007;Curio, 1983), such as foraging (Daunt et al., 2007), mate familiarity (Nisbet & Dann, 2009), or competing for a mate (Perdeck & Cavé, 1992). Meanwhile, within-individual physiological changes, that is, senescence, can be responsible for declines in performance in late adulthood (Hammers et al., 2013;Reed et al., 2008), or terminal investment can result in increased performance (e.g. ...
Age‐related variation in reproductive performance in long‐lived iteroparous vertebrate species is common, with performance being influenced by within‐individual processes, such as improvement and senescence, in combination with among‐individual processes, such as selective appearance and disappearance. Few studies of age‐related reproductive performance have compared the role of these drivers within a metapopulation, subject to varying degrees of resource competition. We accounted for within‐ and among‐individuals changes among known‐aged Adélie penguins (Pygoscelis adeliae) during 17 years (1997 to 2013), at three clustered colonies of disparate size, to understand patterns in age‐related reproductive success during early and late adulthood. Age at first reproduction (AFR) was lowest, and number of breeding attempts highest, at the largest colony. Regardless of AFR, success improved with early post‐recruitment experience. For both oldest and youngest recruitment groups, peak performance occurred at the end of their reproductive lifespan indicating a possible cost of reproduction. Intermediate recruitment groups reached peak performance in their mid‐reproductive lifespan and with intermediate breeding experience, before decreasing. Breeding success was lowest for the initial breeding attempt regardless of AFR, but we observed subsequent variation relative to recruitment age. Gaining experience by delaying recruitment positively influenced reproductive performance early in the reproductive lifespan and was most evident for the youngest breeders. Oldest recruits had the highest initial and peak breeding success. Differences in AFR resulted in tradeoffs in reproductive lifespan or timing of senescence but not in the overall number of breeding attempts. Patterns differed as a function of colony size, and thus competition for resources. Early life improvement in performance at the larger colonies was primarily due to within‐individual factors and at the largest colony, AFR. Regardless of colony size late‐life performance was positively related to the age at last reproduction, indicating selective disappearance of lower performing individuals. These results highlight that different life‐history strategies were equally successful, indicating that individuals can overcome potential tradeoffs associated with early‐ and late‐life performance. These results have important implications for understanding the evolution of life‐history strategies responsible for driving population change.
... Breeding little penguins show high site fidelity, returning each year to either the same nest site or one within a few metres (Reilly and Cullen 1981). Reasons for changing nests are unknown, but may include a change of mate or a failed breeding attempt (Reilly and Cullen 1981;Nisbet and Dann 2009). During the period when there were un-monitored boxes spread among monitored boxes, the penguins likely swapped between the two types and hence in some years were not recaptured, even though they were still alive, and were later recaptured in monitored boxes. ...
Context: Tourism operations that provide the opportunity for wildlife viewing can support conservation management through public education, habitat protection, population management, research activities and revenue generation. However, alongside these potential benefits there can be negative effects on the species that include the possibility of reduced breeding success, survival and, subsequently, population growth.
Aim: We sought to establish whether a tourism operation affected little penguins Eudyptula minor by comparing reproductive and survival parameters of two managed populations in Oamaru, New Zealand. One population was the focus of a tourism operation, whereas the other (located nearby) did not provide any public access. The tourism operation implemented strategies to reduce human disturbance, including the reduction of noise, light and movement from visitors during viewing, and by ensuring that visitors were restricted to designated viewing areas.
Methods: Nesting boxes were installed at both colonies that facilitated weekly monitoring of the populations. The monitoring program (1993–2017) included weekly checks of every nesting box in the colony for the presence of eggs, chicks and adults. Chicks were weighed before fledging, and both fledglings and breeding adults were individually marked.
Key results: Lay dates, breeding success, chick fledge mass and survival rates were not measurably different between the two populations, indicating that there was little evidence of negative effects on the penguins at the tourist site.
Conclusions: The slight differences observed between the colonies during the time series were attributed to environmental damage sustained at the non-tourist site and a difference in the proportion of un-monitored nest sites available to the penguins when the study was initiated.
Implications: Notwithstanding the present findings, long-term and consistent monitoring of wildlife populations facing increasing pressure from tourism is essential to ensure effects are detected and that management procedures implemented to reduce potential effects.
... Chick fledging dates were recorded as the median date of the period between the last sighting of the pre-fledging chick and discovery that the chick had fledged. Chicks that were PIT-tagged were considered to have successfully fledged if they weighed at least 500 g at the time of PIT-tagging and were not found dead prior to fledging (Nisbet and Dann, 2009). Chicks that were not PIT-tagged (due to difficultly accessing them) were considered to have successfully fledged if they were not found dead prior to fledging and if they had lost > 90% of their mesoptyle down feathers when last re-sighted. ...
During the 2011 M/V Rena oil spill in Tauranga, New Zealand, 383 little blue penguins (LBP, Eudyptula minor) were oiled, rescued and rehabilitated, with 90.6% surviving to be released back to the wild. We monitored the post-release breeding success of rehabilitated LBPs to assess the effectiveness of the rehabilitation process. Breeding success was monitored during the first breeding season post-release (2012−13) to assess productivity for both rehabilitated and control penguins (breeding pairs of rehabilitated or non-oiled (control) birds). Egg laying, hatching and fledging success rates for pairs of rehabilitated and control penguins were both within ranges reported for other LBP colonies in Australia and New Zealand. The only significant difference between rehabilitated and control pairs was that hatching success was reduced in the first season after release for rehabilitated pairs. Overall, rehabilitation appeared to reverse most potential negative effects of oiling on the post-release breeding success of rehabilitated LBP.
... sex, age and breeding status) becomes increasingly important as a population declines and may have a significant influence on the ability of that population to increase. The age of a seabird for example is an important factor for successful foraging (Daunt et al. 2007;Zimmer et al. 2011) and reproduction (Limmer and Becker 2009;Nisbet & Dann 2009). Low breeding success in young birds is often hypothesised to be due to lack of experience, poor foraging skills and physical immaturity and there is some evidence that younger hoiho have a lower reproductive success than older birds (Stein et al. 2017b). ...
A review of the marine and terrestrial impacts faced by yellow-eyed penguins | hoiho, as well as recommendations for conservation management and research
... Many previous studies reported no evidence for senescent trends in fitness related characters in the wild. Nisbet and Dann (2009) did not observe senescent trends in nest initiation dates of little penguins (Eudyptula minor), and no age-related decline of reproductive success was observed in the snow petrel (Pagodroma nivea, Berman et al., 2009). The lack of senescent patterns for certain breeding parameters may be explained by the improvement of female experience with age and interactions with external factors such as predation, which is one of the main causes of nest failure (Martin, 1995). ...
In free-ranging populations, age-dependent variation in fitness related parameters, in particular the pattern of senescence, has major eco-evolutionary implications and potential influence on population dynamics. Despite the recent surge of studies of senescence in the wild, senescence patterns in species for which population dynamics assessments are crucial, such as translocated populations, remain virtually unexplored. Based on a 15-year nest survey of a North-African Houbara bustard population in Morocco, we investigated age variation in the breeding performance of captive-bred females released in the wild. We identified 781 females, from 1 to 10 years of age, on 1094 nests. We examined how age influenced nest initiation date, clutch size, egg volume, daily nest survival and daily brood survival, as well as whether age-dependent patterns varied according to environmental conditions. Most breeding parameters exhibited variation, suggesting an increase in breeding performance with age in young females (those from 1 to 3 years old). In older females (> 7–8 years old), the egg volume and clutch size decreased with age, in concordance with expectations from senescence theories and previous empirical results obtained from captive Houbara bustards. Finally, our analysis uncovered a significant interaction between age and the amount of precipitation prior to the breeding season on clutch size, suggesting differential abilities of females of different ages to increase their breeding investment. Our study suggests that life histories in translocated individuals are not affected by translocation protocols and provides insights for implementing age dependencies in population viability assessments.
... Most data on bycatch of little penguins comes from around Phillip Island, southeast Australia (38°S, 145°E), one of the largest colonies of this species (Nisbet & Dann 2009, Dann & Chambers 2013. The majority of little penguins breeding at Phillip Island feed within 15 km of the coast in northern Bass Strait, where there is considerable overlap with gillnets, or in Port Phillip Bay (Collins et al. 1999, Chiaradia et al. 2007, McCutcheon et al. 2011, Pelletier et al. 2014). ...
Penguins are the most threatened group of seabirds after albatrosses. Despite being regularly captured in fishing gear, the threat to penguins, as a group, has not yet been assessed. We reviewed both published and grey literature to identify the fishing gear types that penguins are most frequently recorded in, the most impacted species and, for these susceptible species, the relative importance of bycatch compared to other threats. While quantitative estimates of overall bycatch levels are difficult to obtain, this review highlights that, of the world's 18 species of penguins, 14 have been recorded as bycatch in fishing gear and that gillnets, and to a lesser extent trawls, are the gear types that pose the greatest threats to penguins. Bycatch is currently of greatest concern for yellow-eyed Megadyptes antipodes (Endangered), Humboldt Spheniscus humboldti (Vulnerable) and Magellanic Spheniscus magellanicus penguins (Near Threatened). Penguins face many threats; reducing bycatch mortality in fishing gear will greatly enhance the resilience of penguin populations to threats from habitat loss and climate change that are more difficult to address in the short term. Additional data are required to quantify the true extent of penguin bycatch, particularly for the most susceptible species. In the meantime, it is crucially important to manage the fisheries operating within known penguin foraging areas to reduce the risks to this already threatened group of seabirds.
... The flightless, precocial young of ground-nesting birds experience substantial mortality (Weston and Elgar 2007;Maguire et al. 2009Maguire et al. , 2013Tan et al. 2015). Intraspecific variation in reproductive success is heavily influenced by the survival of young (Bradley et al. 1990;Rogers et al. 1995;Hedrick 2005;Nisbet and Dann 2009;Anteau et al. 2014). Thus mortality of young may influence evolutionary trajectories and, in some cases, even population viability (Loegering and Fraser 1995;Göth and Vogel 2003). ...
... It appears that since the turn of the century, penguins recruit into the breeding population at the earliest possible opportunity. This likely has negative effects on breeding performance since in seabirds age is an important determinant for foraging success (e.g., Daunt et al., 2007;Zimmer et al., 2011) and subsequently reproductive success (e.g., Limmer & Becker, 2009;Nisbet & Dann, 2009). The decline in the mean age of new breeders in recent years indicates that more inexperienced birds are recruiting as breeders, and possibly explains the overall deteriorating reproductive success. ...
Climate change is a global issue with effects that are difficult to manage at a regional scale. Yet more often than not climate factors are just some of multiple stressors affecting species on a population level. Non-climatic factors—especially those of anthropogenic origins—may play equally important roles with regard to impacts on species and are often more feasible to address. Here we assess the influence of climate change on population trends of the endangered Yellow-eyed penguin (Megadyptes antipodes) over the last 30 years, using a Bayesian model. Sea surface temperature (SST) proved to be the dominating factor influencing survival of both adult birds and fledglings. Increasing SST since the mid-1990s was accompanied by a reduction in survival rates and population decline. The population model showed that 33% of the variation in population numbers could be explained by SST alone, significantly increasing pressure on the penguin population. Consequently, the population becomes less resilient to non-climate related impacts, such as fisheries interactions, habitat degradation and human disturbance. However, the extent of the contribution of these factors to declining population trends is extremely difficult to assess principally due to the absence of quantifiable data, creating a discussion bias towards climate variables, and effectively distracting from non-climate factors that can be managed on a regional scale to ensure the viability of the population.
... For example, in long-lived seabird species, a period of poor reproductive success at a young age or at a lower level of experience may be superseded by a period at which the individual performs at their peak reproductive output (Forslund & P€ art, 1995). At an older age, senescence may begin to reduce reproductive output, followed by terminal illness and death (Fowler, 1995;Nisbet & Dann, 2009;Froy et al., 2013). With increasing age, maternal efficiency might allow for control of the timing, size, volume, composition and pore density of eggs, and high levels of pair synchrony through maintenance of long-term pair bonds may reduce incubation periods and increase nesting success (Massaro et al., 2002. ...
Longitudinal studies focusing on lifetime reproductive success (LRS) have been used to measure individual breeding performance and identify commonalities among successful breeders. By extending the focus to subsequent generations we identify a proportion of high-quality individuals that contribute disproportionately to the population over multiple generations. We used 23 years of yellow-eyed penguin (Megadyptes antipodes) breeding data from one breeding area to identify the proportion of individual birds that raised successful breeders, which in turn raised offspring. We explored which life-history components influenced LRS, as this knowledge would enable conservation resources to be focused on high-performing individuals in this endangered population. From 2,147 birds marked as chicks, 370 (17.2%) survived to adulthood and recruited to their natal location, of which 219 (10.2%) fledged offspring: 124 (56.6%) of the 219 birds produced offspring that recruited as breeders. Only 102 birds (4.8% of 2,147) fledged first-generation offspring that in turn fledged offspring (second-generation offspring, or grand-offspring). We found that ∼25% of the birds that survived to breed had above-average LRS as well as above-average numbers of grand-offspring, and were more likely to have produced first-generation chicks that recruited and also produced above-average numbers of second-generation chicks. Our findings suggest that there is a core of “super-breeders” that contribute disproportionately to the population over successive generations. Lifespan and age-at-first-breeding were correlated with LRS. We suggest that traits of birds relating to longevity, health (e.g., immunocompetence) and fitness could be examined to identify potential links with high LRS and inter-generational fecundity. “Super-breeders” appear to consistently achieve high LRS and long lifespans in a stochastic environment, demonstrating greater resilience in the face of extreme events.
... Individual quality does not necessarily predict the breeding success of a pair [1][2][3]. Instead, pair compatibility has been proposed to influence success because of synergistic effects between pair members [4,5]. Furthermore, in several bird species, breeding success is positively related to pair-bond duration [6][7][8][9]. ...
Background
Pair compatibility affects the success of a pair; however, its causes and mechanisms are not fully understood. Vocal exchange may be very important for pair formation, coordinating pair activities, maintaining the pair bond and mate guarding. To investigate the role of vocal exchange in pair formation and pair maintenance, we explored whether new and established pairs of zebra finches differed in their calling relationships. We used individualised backpack microphones to examine the entire daily vocal emission of pairs, with parallel video recording of behaviour. ResultsWe found that in non-breeding, isolated pairs, a specific type of call, the “stack call”, was the most common. Furthermore, all pairs used the stack call for precisely timed antiphonal exchange. We confirmed a difference between new and established pairs in social behaviour, with the former spending less time in physical contact. Notably, we found that this was mirrored by a difference in calling behaviour: members of new pairs converged over time on a more symmetric calling relationship. Additionally, we observed different response rates to partners among individuals, but a repeatable relationship of answering within pairs, which may reflect different degrees of motivation to answer the partner. Conclusions
Our findings show that there is plasticity in calling behaviour and that it changes during pair formation, resulting in a coordinated stack call exchange with a similar number of answers between partners once the pair is established. It is possible that some of the calling relationship measurements that we present reflect pair compatibility.
... For both AT and SST, only data between August and December were used because they covered the time period when little penguins regularly attend their breeding sites at all of the monitored colonies and a single breeding attempt takes 3 months from egg laying to fledgling. Furthermore, data for the last 10 years (2003-2014), and not just the study years,were used because little penguins are expected to live at least 10 years in the wild(Dann et al., 2005;Nisbet & Dann, 2009), and the age of the individuals was unknown in this study. Mean water depths (WD) ...
Morphological variation between populations of the same species can arise as a response to genetic variation, local environmental conditions, or a combination of both. In this study, I examined small-scale geographic variation in bill size and body mass in little penguins (Eudyptula minor) across five breeding colonies in South Australia separated by <150 km. To help understand patterns driving the differences, I investigated these variations in relation to environmental parameters (air temperature, sea surface temperature, and water depth) and geographic distances between the colonies. I found substantial morphological variation among the colonies for body mass and bill measurements (except bill length). Colonies further located from each other showed greater morphological divergence overall than adjacent colonies. In addition, phenotypic traits were somewhat correlated to environmental parameters. Birds at colonies surrounded by hotter sea surface temperatures were heavier with longer and larger bills. Birds with larger and longer bills were also found at colonies surrounded by shallower waters. Overall, the results suggest that both environmental factors (natural selection) and interpopulation distances (isolation by distance) are causes of phenotypic differentiation between South Australian little penguin colonies.
... For example, in long-lived seabird species, a period of poor reproductive success at a young age or at a lower level of experience may be superseded by a period at which the individual performs at their peak reproductive output (Forslund & P€ art, 1995). At an older age, senescence may begin to reduce reproductive output, followed by terminal illness and death (Fowler, 1995;Nisbet & Dann, 2009;Froy et al., 2013). With increasing age, maternal efficiency might allow for control of the timing, size, volume, composition and pore density of eggs, and high levels of pair synchrony through maintenance of long-term pair bonds may reduce incubation periods and increase nesting success (Massaro et al., 2002. ...
Longitudinal studies focusing on lifetime reproductive success (LRS) have been used to measure individual breeding performance and identify commonalities among successful breeders. By extending the focus to subsequent generations we identify a proportion of high-quality individuals that contribute disproportionately to the population over multiple generations. We used 23 years of yellow-eyed penguin (Megadyptes antipodes) breeding data from one breeding area to identify the proportion of individual birds that raised successful breeders, which in turn raised offspring that bred successfully. We explored which life-history components influenced lifetime reproductive success, as this knowledge would enable conservation resources to be focused on high-performing individuals in this endangered population. From 2147 birds marked as chicks, 370 (17.2%) survived to adulthood and recruited to their natal location, of which 219 (10.2%) fledged offspring: 124 (56.6%) of the 219 birds produced offspring that recruited as breeders. Only 102 birds (4.8% of 2147) fledged first-generation offspring that in turn fledged offspring (second-generation offspring, or grand-offspring). We found that c. 26% of the birds that survived to breed had above-average LRS as well as above-average numbers of grand-offspring, and were more likely to have produced first-generation chicks that recruited and also produced above-average numbers of second-generation chicks. Our findings suggest that there is a core of “super-breeders” that contribute disproportionately to the population over successive generations. Lifespan and age-at-first-breeding were correlated with LRS. We suggest that traits of birds relating to longevity, health (e.g. immunocompetence) and fitness could be examined to identify potential links with high LRS and inter-generational fecundity. “Super-breeders” appear to consistently balance high LRS with long- life-span in a stochastic environment, demonstrating greater resilience in the face of extreme events.
... This lag of several months in the effect of wind on survival is similar to previously noted lags in the effect of sea surface temperature on the timing of breeding [8] and of the temperature gradient on adult mass and timing of breeding [20]. The effect may be indirectfor example, good feeding conditions in the winter preceding breeding allow adults to progress through the breeding season in better condition, possibly breed earlier [21] and confer the advantage to their chicks through greater meal masses, higher fledging weights and consequently higher first year survival [9]. Conversely it may be direct-for example, a better food supply for chicks postfledging because of processes commencing in winter several months earlier. ...
We live in an age of increased awareness of climate change and its potential eects on our ecosystems. Here we look at the eect of one aspect of climate, directional wind components, on the survival of Little Penguins Eudyptula minor on Phillip Island in southeastern Australia, using mark-recapture data gathered over a 42 year period since 1968. We apply biologically realistic age structures for the survival and recapture probabilities, and use mean seasonal wind magnitudes from the four cardinal compass directions as covariates in our modelling of the survival probability. Results indicate that rst year survival is most aected by southerly winds in the winter prior to the chick’s
... However, mean laying date may range from early September (September the 7th in 2002) to mid-November (November the 17th in 2007). Age and individual quality can influence the onset of reproduction (Chiaradia and Nisbet, 2006;Nisbet and Dann, 2009). But at population level, little penguins respond to inter-annual variations in relevant oceanographic features and marine productivity patterns, probably driving patterns in the availability and distribution of prey (Afán et al., 2015). ...
Marine top and meso predators like seabirds are limited by the need to breed on land but forage on limited or patchily distributed resources at sea. Constraints imposed by such central-place foraging behavior change during breeding or even disappear outside the breeding period when there is no immediate pressure to return to a central place. However, central place foraging is usually factored as an unchanging condition in life history studies. Here we used little penguin Eudyptula minor, a resident bird with one of the smallest foraging range among seabirds, to examine the different degree of pressure/constraints of being a central-place forager. We combined data on isotopic composition (δ13C and δ15N), conventional stomach contents and body mass of little penguins breeding at Phillip Island, Australia over 9 years (2003–2011). We explored relationships between diet and body mass in each stage of the breeding season (pre-laying, incubation, guard, and post-guard) in years of “high” and “low” reproductive success. Values of δ13C and δ15N as well as isotopic niche width had similar patterns among years, with less variability later in the season when little penguins shorten their foraging range at the expected peak of their central-place foraging limitation. Body mass peaked before laying and hatching in preparation for the energetically demanding periods of egg production and chick provisioning. An increase of anchovy and barracouta in the diet, two major prey for little penguins, occurred at the critical stage of chick rearing. These intra-annual trends could be a response to imposed foraging constraints as reproduction progresses, while inter-annual trends could reflect their ability to match or mismatch the high energy demanding chick rearing period with the peak in availability of high-quality prey such as anchovy. Our findings underline the key advantages of using a stable isotope approach combined with conventional dietary reconstruction to reveal an otherwise intractable ecological issue of different constrains of being a central-place forager, such as the little penguin, which could be applied to other marine species.
... Box 1. Ecological and Evolutionary Importance of Long-Term Studies Studies that have followed individuals throughout their lives have yielded important insights into demographic and lifehistory parameters of wild populations which cannot be obtained from cross-sectional programs. They have provided details on the impact of age, individual quality, status of pair-bond and food abundance on aspects of breeding, recruitment and survival [11][12][13][14][15][16][17][18][19][20][21][22][23][24]; cost of breeding [25]; inbreeding [26][27][28]; senescence [29][30]; mate choice [31][32]; carry-over and transgenerational effects [33][34][35][36][37] and lifetime reproduction [38][39]. Studies that assembled pedigrees from observational and or molecular techniques have enabled widespread application of quantitative genetic methods to questions in evolutionary ecology, such as maintenance of genetic variance, inheritance of fitness components and the relative contribution of plasticity and micro-evolutionary processes to phenotypic change [40][41][42][43][44][45][46][47]. ...
The recent trend for journals to require open access to primary data included in publications has been embraced by many biologists, but has caused apprehension amongst researchers engaged in long-term ecological and evolutionary studies. A worldwide survey of 73 principal investigators (Pls) with long-term studies revealed positive attitudes towards sharing data with the agreement or involvement of the PI, and 93% of PIs have historically shared data. Only 8% were in favor of uncontrolled, open access to primary data while 63% expressed serious concern. We present here their viewpoint on an issue that can have non-trivial scientific consequences. We discuss potential costs of public data archiving and provide possible solutions to meet the needs of journals and researchers.
... Breeding success on Granite Island varied greatly between years, and went as low as 0.23 fledglings per pair in 2001. Such variation in breeding success is common in little penguins, as demonstrated by long-term studies on Phillip and Bowen Islands, where annual breeding success varied from 0.08 to 1.38 fledglings per pair (Reilly and Cullen 1981;Nisbet and Dann 2009) on Phillip Island and from 0.70 to 1.83 fledglings per pair on Bowen Island (Fortescue 1999). Because of the limited foraging ranges of the little penguins during the breeding season (Collins et al. 1999;Saraux et al. 2011b), high breeding success (and heavy chick mass at fledgling) is generally a good indicator of high food availability (e.g. ...
Over the past decade, populations of little penguins (Eudyptula minor) have been seriously declining across South Australia for reasons still not fully understood. In the present study, I investigated breeding performance and return rates of little penguins on Granite Island for 17 years in relation to patterns of population decline. I focussed on the impacts of human disturbance, breeding site, abandonment and predation on breeding success. The average breeding success was 1.05±0.12 fledglings per pair; and breeding success increased since 1990, despite population decline. Breeding site was the main factor affecting breeding success. I found no effect of predation or abandonment on breeding success, but there was a negative effect of predation on the number of dead chicks found. In addition, I found a negative effect of human disturbance. Despite the observed increase in breeding success, return rates were extremely low for both adults (16.3%) and fledglings (2.3%). Population modelling confirmed the observed population decline on Granite Island, with subadult survival being the most critical variable affecting population growth. The present study thus highlighted the need for further studies into factors affecting survival of adults and subadults.
... Finally, breeding success was affected by the age of individuals and by the breeding initiation date, which is itself influenced by the individual breeding quality. Our results are consistent with numerous studies on several long-lived species, with younger breeders, and/or individuals of lower breeding quality performing less well in terms of breeding activities than older breeders and/or individuals with greater breeding quality (Forslund and Pärt 1995;DeForest and Gaston 1996;Bowen et al. 2006;Ezard et al. 2007;Nisbet and Dann 2009;Moyes et al. 2011;Froy et al. 2013). As observed in other species, this lower breeding success has also been Illustration of the feeding routes taken by king penguins from Crozet archipelago during the austral summer (incubation period in solid dark line and brooding period in solid gray line) and winter (crèching period in dashed black line) (adapted from Charrassin and Bost 2001;Bost et al. 2004). ...
The variability in individual fitness within a population is likely to be mediated through individual foraging ability and tactics, themselves linked to age- or experience-related processes, but also to differences in individual quality. Not only age, experience, and quality but also sex-related foraging strategies should particularly play an important role in long-lived central-place foragers that have to cope with strong environmental constraints. We monitored the foraging effort (foraging trip durations and number of trips) of 262 known-age micro-tagged king penguins, Aptenodytes patagonicus, at different breeding stages during one of their breeding cycles. We investigated how their age (4–11 years old), sex, past breeding experience (the number of successful breeding attempts), and breeding quality (the expected breeding success, corresponding to the residual of the linear relationship between the age and on the number of past breeding success divided by the number of breeding attempts) affected foraging over a whole breeding season. During the incubation, younger birds (4 years old) undertook longer foraging trips compared with older ones. During the brooding phase and the second period of the crèching phase, more experienced birds performed shorter foraging trip than those with a low breeding experience, whereas, during the first period of the crèching phase, individuals with better breeding quality performed shorter foraging trips at sea than low breeding quality individuals. Sex-specific foraging patterns were also observed depending on the period of the breeding cycle. Our study shows, for the first time, how foraging effort can be driven by a complex interplay of several individual parameters according to breeding stage and resource availability and abundance.
... Studies that have followed individuals throughout their lives have yielded important insights into demographic and lifehistory parameters of wild populations which cannot be obtained from cross-sectional programs. They have provided details on the impact of age, individual quality, status of pair-bond and food abundance on aspects of breeding, recruitment and survival [11][12][13][14][15][16][17][18][19][20][21][22][23][24]; cost of breeding [25]; inbreeding [26][27][28]; senescence [29][30]; mate choice [31][32]; carry-over and transgenerational effects [33][34][35][36][37] and lifetime reproduction [38][39]. Studies that assembled pedigrees from observational and or molecular techniques have enabled widespread application of quantitative genetic methods to questions in evolutionary ecology, such as maintenance of genetic variance, inheritance of fitness components and the relative contribution of plasticity and micro-evolutionary processes to phenotypic change [40][41][42][43][44][45][46][47]. ...
The recent trend for journals to require open access to primary data included in publications has been embraced by many biologists, but has caused apprehension amongst researchers engaged in long-term ecological and evolutionary studies. A worldwide survey of 73 principal investigators (Pls) with long-term studies revealed positive attitudes towards sharing data with the agreement or involvement of the PI, and 93% of PIs have historically shared data. Only 8% were in favor of uncontrolled, open access to primary data while 63% expressed serious concern. We present here their viewpoint on an issue that can have non-trivial scientific consequences. We discuss potential costs of public data archiving and provide possible solutions to meet the needs of journals and researchers.
... We also found that breeding performances (breeding duration and breeding success) were affected by past breeding success. Our results are consistent with several studies on long-lived species, younger breeders and/or breeders with lower quality generally performing less well in terms of breeding than older breeders and/or individuals of greater quality (in seabirds; DeForest and Gaston 1996;Ezard et al. 2007, in mammals;Moyes et al. 2009Moyes et al. , 2011Nisbet and Dann 2009;Froy et al. 2013). Not surprisingly breeding performances were also explained by breeding date initiation as previously reported in king penguin (Weimerskirch et al. 1992;Stier et al. 2014) and other seabird species (DeForest and Gaston 1996;Ezard et al. 2007;McCleery et al. 2008). ...
Growing evidence suggests that telomeres, non-coding DNA sequences that shorten with age and stress, are related in an undefined way to individual breeding performances and survival rates in several species. Short telomeres and elevated shortening rates are typically associated with life stress and low health. As such, telomeres could serve as an integrative proxy of individual quality, describing the overall biological state of an individual at a given age. Telomere length could be associated with the decline of an array of physiological traits in age-controlled individuals. Here, we investigated the links between individuals’ relative telomere length, breeding performance and various physiological (body condition, natural antibody levels) and life history (age, past breeding success) parameters in a long-lived seabird species, the king penguin Aptenodytes patagonicus. While we observed no link between relative telomere length and age, we found that birds with longer telomeres arrived earlier for breeding at the colony, and had higher breeding performances (i.e. the amount of time adults managed to maintain their chicks alive, and ultimately breeding success) than individuals with shorter telomeres. Further, we observed a positive correlation between telomere length and natural antibody levels. Taken together, our results add to the growing evidence that telomere length is likely to reflect individual quality difference in wild animal.
... Female age played a fundamental role in modulating resource allocation strategies at the individual level. Age, an index of foraging experience and perhaps body condition, has been considered as the most relevant factor affecting foraging and breeding performance in little penguins (Nisbet and Dann, 2009;Pelletier et al., 2014;Zimmer et al, 2011). More experienced and better-conditioned middle-aged (5-10 years) little penguins forage better than inexperienced younger (3-4 years) and poorer-conditioned but experienced older (11-14 years) individual females (Zimmer et al., 2011). ...
... Increases in wait time for food can weaken chicks, lower their ability to digest large meals (Yang et al., 2009), and, in cases of severe food deprivation, lower their corticosterone levels which may cause less vigorous begging (Walker et al., 2005b). The foraging behavior and success of individual seabirds vary for a variety of reasons including age, experience, pair-bond duration, body condition, and other intrinsic factors (Harris et al., 2014a;Lewis et al., 2009;Nisbet and Dann, 2009). Individual seabirds are often consistent (Harris et al., 2014b), so some individuals contribute more to future generations in a population (Annett and Pierotti, 1999). ...
... All penguin burrows within plots were inspected for the presence of adults, chicks or eggs and all occupied burrows were counted. Surveys were conducted to coincide with the peak period of burrow occupancy during the breeding season, which usually occurs in the Austral Spring and Summer between August and February (Nisbet and Dann 2009). However, burrow occupancy varies at an unknown rate because breeding by Little Penguins is not tightly synchronised in time or space. ...
Estimates of population size and changes through time are critical for setting conservation priorities. The distribution of little penguins Eudyptula minor on Phillip Island has contracted substantially over the last century and is now restricted almost entirely to the Summerland Peninsula. Trends in penguin numbers on the Peninsula have been assessed near the periphery of the colony and suggest two-fold fluctuations since 1977. Here we present data on population dynamics of little penguins from 1984 to 2009 from systematic burrow surveys conducted across the entire colony. We have developed a new and robust technique to model true breeding population size from burrow counts by applying a correction for burrow occupancy rates and population abundances estimated simultaneously at eight monitoring sites where marked penguins were checked at fortnightly intervals. Using 148 quadrants across the Peninsula counted twice during the breeding season we estimate that the number of breeding penguins on Phillip Island is currently about 28,700 (26,382 – 31,018). We explore the likely drivers of observed population changes by modelling population dynamics as a function of extrinsic factors and intrinsic demographic variables.
... During the breeding season, little penguins are centralplace foragers, restricted to foraging areas close to their nest, and are therefore vulnerable to small regional changes in prey abundance and distribution (Chiaradia et al. 2007). In Australia, changes in food availability for the little penguin have resulted in delays to the start of the breeding period and a subsequent reduced likelihood of the production of a second clutch, increased mortality of chicks, and poor adult and chick body condition, resulting in reduced chick immunity and longer fledging periods (Reilly & Cullen 1981;Nisbet & Dann 2009;Chiaradia et al. 2010). In New Zealand, the lack of information about diet makes it impossible to identify any changes in prey availability that may occur, which may be responsible for seasons of poor reproductive success. ...
At-sea shifts in food quality and availability can affect populations of marine birds; however, it is difficult to evaluate the impacts of changes in prey composition and availability without some baseline information on diet composition. The little penguin (Eudyptula minor) is a common inshore-feeding seabird in New Zealand and Australia. To date, only two dietary studies have been undertaken on the little penguin in New Zealand, at two widely separated locations. This study recorded diet of little penguins during the chick- rearing stage of breeding at three colonies in southern New Zealand. Sixty-nine stomach samples were acquired via the stomach flushing technique at Banks Peninsula, Oamaru, and Stewart Island. Prey composition differed between each site: (1) at Oamaru, Graham’s gudgeon (Grahamichthys radiata) occurred most frequently (100%) and contributed the most to meal mass (92.1%); (2) at Banks Peninsula arrow squid (Nototodarus sloanii) occurred most frequently (87.5%), but two fish species – slender sprat (Sprattus antipodum) (33.9%) and ahuru (Auchenoceros punctatus) (37.4%) – contributed most to meal mass; and (3) at Stewart Island arrow squid occurred most frequently (91.3%), and contributed most to meal mass (73.1%). Little penguins take a wide diversity of species, and may switch between species, probably in response to temporal variation in availability. In New Zealand, little penguins ate higher proportions of lower quality cephalopods than those in Australia. As top predators in the marine ecosystem, changes in little penguin diet may indicate changes occurring in the inshore marine ecosystem.
... However, recently, the existence of senescence in the wild has been demonstrated in a number of organisms (e.g., Jones et al. 2008), and two opposite theories on life-history strategies while aging have been described in the literature in the presence of senescence: 1 The terminal investment theory, where old individuals enhance their last forces to some last reproduction events if their condition becomes critical (McNamara et al. 2009;Froy et al. 2013). This theory has received relatively little empirical evidence, some in wild ungulates (Clutton-Brock 1984;Ericsson et al. 2001;Weladji et al. 2010) and in a marsupial (Isaac and Johnson 2005), or in manipulative studies that experimentally increased internal damage in seabirds (Velando et al. 2006) and insects (Morrow et al. 2003). 2 Old individuals might instead reduce inherently their investment in reproduction by diminishing clutch size (Nisbet and Dann 2009) or reducing their breeding frequency (Catry et al. 1998;McElligott et al. 2002), which might help maintaining survival as predicted by the life-history theory (Stearns 1992). However, despite the observation that age variation in several life-history traits has consistently been detected in a number of species (Jones et al. 2008) and that it has been well established that several life-history traits are state dependent (McNamara and Houston 1996), few studies have examined state-dependent variation in lifehistory traits with aging which is particularly relevant with respect to senescence (Tavecchia et al. 2005;Descamps et al. 2009;Robinson et al. 2012). ...
Allocation decisions depend on an organism's condition which can change with age. Two opposite changes in life-history traits are predicted in the presence of senescence: either an increase in breeding performance in late age associated with terminal investment or a decrease due to either life-history trade-offs between current breeding and future survival or decreased efficiency at old age. Age variation in several life-history traits has been detected in a number of species, and demographic performances of individuals in a given year are influenced by their reproductive state the previous year. Few studies have, however, examined state-dependent variation in life-history traits with aging, and they focused mainly on a dichotomy of successful versus failed breeding and non-breeding birds. Using a 50-year dataset on the long-lived quasi-biennial breeding wandering albatross, we investigated variations in life-history traits with aging according to a gradient of states corresponding to potential costs of reproduction the previous year (in ascending order): non-breeding birds staying at sea or present at breeding grounds, breeding birds that failed early, late or were successful. We used multistate models to study survival and decompose reproduction into four components (probabilities of return, breeding, hatching, and fledging), while accounting for imperfect detection. Our results suggest the possible existence of two strategies in the population: strict biennial breeders that exhibited almost no reproductive senescence and quasi-biennial breeders that showed an increased breeding frequency with a strong and moderate senescence on hatching and fledging probabilities, respectively. The patterns observed on survival were contrary to our predictions, suggesting an influence of individual quality rather than trade-offs between reproduction and survival at late ages. This work represents a step further into understanding the evolutionary ecology of senescence and its relationship with costs of reproduction at the population level. It paves the way for individual-based studies that could show the importance of intra-population heterogeneity in those processes.
... This lag of several months in the effect of wind on survival is similar to previously noted lags in the effect of sea surface temperature on the timing of breeding [8] and of the temperature gradient on adult mass and timing of breeding [20]. The effect may be indirectfor example, good feeding conditions in the winter preceding breeding allow adults to progress through the breeding season in better condition, possibly breed earlier [21] and confer the advantage to their chicks through greater meal masses, higher fledging weights and consequently higher first year survival [9]. Conversely it may be direct-for example, a better food supply for chicks postfledging because of processes commencing in winter several months earlier. ...
We live in an age of increased awareness of climate change and its potential effects on our ecosystems. Here we look at the effect of one aspect of climate, directional wind components, on the survival of Little Penguins Eudyptula minor on Phillip Island in southeastern Australia, using mark-recapture data gathered over a 42 year period since 1968. We apply biologically realistic age structures for the survival and recapture probabilities, and use mean seasonal wind magnitudes from the four cardinal compass directions as covariates in our modelling of the survival probability. Results indicate that first year survival is most affected by southerly winds in the winter prior to the chick's birth, which increase survival, and by easterly winds in the summer of hatching/fledging, which decrease survival. Adult survival is most affected by increasing northerly winds in the autumn following moult two pages per sheet of paper.) Copies of this article must not be made otherwise available on the internet; instead link directly to this url for this article. Contents C1013 (positively) and by easterly winds in the preceding summer (negatively). For both first-year and adult birds, increasing easterly summer wind is associated with decreased survival, possibly due to reduced flows of nutrient rich waters from western Bass Strait.
Age-related changes in parental phenotypes or genotypes can impact offspring fitness, but separating germline from nongermline transgenerational effects of ageing is difficult for wild populations. Further, in cooperatively breeding species, in addition to parental ages, the age of 'helpers' attending offspring may also affect juvenile performance. Using a 30-year study of a cooperative breeder with very high rates of extra-pair paternity, the superb fairy-wren (Malurus cyaneus), we investigated the effects of maternal, paternal and helper ages on three measures of offspring performance: nestling weight, juvenile survival to independence and recruitment to the breeding population. Mothers with a longer lifespan had offspring with higher juvenile survival, indicating selective disappearance, but the effect of maternal age on juvenile survival was of similar magnitude but negative. For extra-pair offspring, there was no evidence of any effect of the ages of either the genetic sire or the cuckolded 'social' father. However, for within-pair offspring, there was a positive effect of paternal age on juvenile survival, which we suggest may be driven by sexual selection. There were positive associations between the average age of helpers attending a nest and two of the three aspects of offspring performance; these effects were stronger than any of the effects of parental age. In general, the multiple associations between offspring fitness and the ages of adults around them appeared to be driven more by age-related changes in environmental effects than by age-related changes in the germline.
Urbanization is a global trend. The United Nations predicts that nearly 70% of the population will dwell in urban area in 2050, so studies of urban ecosystems becomes increasingly important. Also, Urbanization creates novel ecosystems, and lets many birds reside here. The Malayan night herons (Gorsachius melanolophus) in Taiwan is a good example. This study explored the survival strategies of the rapid growth and the factors affecting nest-site selection for Malayan night herons in urban park and green space. From March to October in 2019, we investigated the nest-site distribution, breeding performance, nest-site characteristics, nest tree characteristics, and nest-site habitat use of the Malayan night heron in 5 sampling areas, including Daan Forest Park, Chiang Kai-shek Memorial Hall, Youth Park, National Taiwan University Campus and 228 Peace Park in Taipei City. The results showed that the overall hatching rate and survival rate of chicks of the urban Malayan night herons were both over 90 %, the reproductive success was 95.74%, and there were two periods of breeding peak during the breeding season. The nests are located on branches with forks and the inclination is close to horizontal. The canopy coverage of the nests is at least 70 % and the nest trees are those with larger diameter at breast height and the crown width. The Malayan night herons build nests on lower crown, and the habitats under the nest-sites are mostly a land type with a human activity environment. The predators are not easy to access in the urbanized environment, which increases the reproductive success, coupled with sufficient breeding resources and increasing productivity, which is conducive to survive in urban. The Malayan night herons chose to nest on stable branches, where is also beneficial for them to monitor the potential human activities, which is one of the reasons why they can adapt to the urban environment. This study expects to have a better understanding of the urban ecosystem by exploring the nest-site selection behavior of the Malayan night heron breeding in urban area.
Declines in reproductive performance among older age classes have been reported in many bird and mammal species, and are commonly presented as demonstrating reproductive senescence. However, no declines in performance could be demonstrated in studies of several bird species. We measured reproductive performance in Common Terns (Sterna hirundo) of known age (2–28 yr) during a 19-yr period at a site in Buzzards Bay, Massachusetts, USA. We measured 6 components of reproductive performance and used generalized additive mixed models (GAMMs) in a Bayesian framework to analyze dependence of each measure on parental age, while controlling for variations among years and indices of individual quality. Four measures of performance improved (earlier laying date, higher values of clutch size, fledging success, and productivity) with age, most rapidly between ages 2 and 10 yr; egg mass and hatching success varied only slightly with age. No measure of performance showed reversals among the older age classes; fledging success and productivity continued to increase through at least age 22 yr. These findings are consistent with results from an earlier study of the same species. Continued increase in reproductive performance through the oldest age classes is not incompatible with “reproductive senescence” (decline in physiological or other functions required for successful reproduction) if either reproductive effort or efficiency continue to increase. Studies within our population have yielded no evidence for age-related increase in reproductive effort, but 3 studies have suggested that older Common Terns can raise chicks more successfully than younger birds without increasing reproductive effort, probably by more efficient foraging and chick provisioning. Our findings suggest that Common Terns offset reproductive senescence by continuing to improve efficiency through at least age 22 yr. Age-related changes in efficiency should be investigated in other species with similar life-history traits.
Breeding performance of many vertebrate species is known to improve over the early stages of the life cycle, which has been commonly attributed to the progressive improvement in competences and increasing investment in reproduction. While there is a large body of evidence for age-related variation in fecundity within bird populations, much less is known on whether and how age affects other traits related to reproduction. The aim of this study was to test for age-related patterns in fecundity, nest-site location, offspring condition and brood sex ratio in a long-lived colonial waterbird, the Great Cormorant (Phalacrocorax carbo sinensis). For this purpose we collected data on 180 breeding attempts of 100 Great Cormorants aged two to 11 years. We found a progressive increase in reproductive output with age and we showed that older individuals nested closer to the colony centre and in higher nesting densities. We also found that parental age was positively related to physiological condition of offspring (measured with whole-blood haemoglobin concentration and plasma glucose concentration). There was no indication for age-related adjustments in brood sex ratio in our cormorant population. Our results indicate a great complexity of the processes which produce age-related improvements in reproductive performance within avian populations.
Life-history strategies have evolved in response to predictable patterns of environmental features. In practice, linking life-history strategies and changes in environmental conditions requires comparable space-time scales between both processes, a difficult match in most marine system studies. We propose a novel spatio-temporal and dynamic scale to explore marine productivity patterns probably driving reproductive timing in the inshore little penguin (Eudyptula minor), based on monthly data on ocean circulation in the Southern Ocean, Australia. In contrast to what occurred when considering any other fixed scales, little penguin's highly variable laying date always occurred within the annual peak of ocean productivity that emerged from our newly defined dynamic scale. Additionally, local sea surface temperature seems to have triggered the onset of reproduction, acting as an environmental cue informing on marine productivity patterns at our dynamic scale. Chlorophyll-a patterns extracted from this scale revealed that environment factors in marine ecosystems affecting breeding decisions are related to a much wider region than foraging areas that are commonly used in current studies investigating the link between animals' life history and their environment. We suggest that marine productivity patterns may be more predictable than previously thought when environmental and biological data are examined at appropriate scales.
© 2015 The Author(s) Published by the Royal Society. All rights reserved.
Competition for food resources can result in spatial and dietary segregation among individuals from the same species. Few studies have looked at such segregations with the combined effect of sex and age in species with short foraging ranges. In this study we examined the 3D spatial use of the environment in a species with a limited foraging area. We equipped 26 little penguins (Eudyptula minor) of known age, sex, and breeding output with GPS (location) and accelerometer (body acceleration and dive depth) loggers. We obtained dietary niche information from the isotopic analysis of blood tissue. We controlled for confounding factors of foraging trip length and food availability by sampling adults at guard stage when parents usually make one-day trips. We observed a spatial segregation between old (>11 years old) and middle-aged penguins (between 5 and 11 years old) in the foraging area. Old penguins foraged closer to the shore, in shallower water. Despite observing age-specific spatial segregation, we found no differences in the diving effort and foraging efficiency between age classes and sexes. Birds appeared to target similar prey types, but showed age-specific variation in their isotopic niche width. We hypothesize that this age-specific segregation was primarily determined by a "cohort effect" that would lead individuals sharing a common life history (i.e. having fledged and dispersed around the same age) to forage preferentially together or to share similar foraging limitations.
An eight-year study was conducted on the breeding biology of the little penguin population at Lion Island. Forwards-selection Poisson regressions were used to determine whether variables such as year, date of lay, years since banding of each parent (indicator of age) and habitat influenced the fledgling numbers and average fledgling weight for adult pairs. 'Date of lay' provided the most significant model of fledgling numbers, while 'habitat' and 'year' as single-variable models also significantly influenced fledgling numbers. 'Date of lay' provided the most significant model of average fledgling weight. Future monitoring of the Lion Island colony therefore should focus on monitoring egg laying at the start of the breeding season, and maintaining high-quality nesting habitat.
The size of eggs, laying intervals, incubation periods, hatching success and
causes of egg mortality in Little Penguins,
Eudyptula minor, were studied on Phillip Island,
Victoria. The mean laying interval was 3 days (range 2–7 days); the mean
incubation period was 35.4 days (range 33–44 days). Second-laid eggs
were shorter and broader than first-laid eggs without any difference in
weight, volume or hatching success. Single-egg clutches had a much lower
success than two-egg clutches. Hatching success varied from 47% to
87% (mean 67%) between 1968–69 and 1998–99 and the
main cause of egg mortality was desertion. It is suggested that annual
fluctuations in hatching success may be linked to annual variations in food
availability through the failure of some birds to relieve their partners
before they are forced to desert the eggs.
Examined breeding succes, body mass changes and survival of Eudyptula minor at four sites on the Summerland Peninsula on Phillip Island in Victoria, SE Australia, between 1984-1991. Data suggested that there was no cost of reproduction in terms of survival or future reproductive output.
We measured parental care (attendance patterns, foraging trip durations
and meal sizes) and chick growth patterns in 45–54 pairs of Little
Penguins during five breeding seasons at a breeding colony in southeast Australia
. Chick survival and productivity were
‘good’ in two years, ‘bad’ in two years and intermediate in the fifth;
these differences probably reflected changes in food availability. In ‘bad’
years, parents lengthened foraging trip durations from 1–2 days to 2–5
days, and shortened the length of the guard period by 25%. Meal sizes
varied strongly with chick age, but were reduced only slightly in the
‘bad’ year and varied only slightly with the number of chicks in the
brood and with the number of parents visiting the nest. Hence, food
intake by chicks depended mainly on the frequency of feeds rather than
on meal size. Chicks responded to reduced provisioning rates both by
reducing mass growth (‘imposed’ response) and by delaying development
(‘induced’ response). The chicks’ responses were primarily
‘imposed’ during the period of rapid growth (days 13–35), but were
mixed and more varied later in the period of development. The ability of
Little Penguins to adjust their foraging behaviour to reduced food availability
is probably constrained by their short foraging range (< 20 km)
and their nocturnal behaviour at the breeding colony, which limits foraging
trip durations to discrete numbers of days.
In avian species with no obvious differences in plumage or body size between the sexes, such as penguins, discriminant function analysis (DFA) of morphometric measurements that display sexual dimorphism can provide a simple and rapid means of determining sex in the field. Like most other penguin species, the Little Penguin (Eudyptula minor) displays sexual dimorphism in bill shape and size. In the present study, discriminant functions (DFs) were developed for sexing adult Little Penguins at two colonies in northern Bass Strait, Victoria, Australia, and their accuracies were compared with those obtained previously in other parts of the species' range. Backwards stepwise DFA indicated that birds at Phillip Island can be sexed with an accuracy of 91% using a single measurement of bill depth (>13.33 mm classed as males). Similar analyses at Gibson Steps produced a DF incorporating bill length, bill depth and head length [ although the model with the greatest accuracy when applied to birds from Phillip Island ( 91%) also contained only bill depth]. Published DFs derived in New Zealand had accuracies of 50-85% when applied to birds from Phillip Island and Gibson Steps, supporting earlier suggestions that DFs are not applicable across subspecies of the Little Penguin. In contrast, there was little difference between the accuracy of the DFs in the present study and that previously derived for the same subspecies in Tasmania when applied to birds from Phillip Island (89%) and Gibson Steps (92%). However, as the degree of variation in bill size within a subspecies is unknown it may still be prudent to derive colony-specific DFs.
Although there is general consensus about the existence of senescence in vertebrates, empirical evidence of senescence in demographic parameters in wild populations is limited. Data on breeding success and survival of breeding common guillemots Uria aalge were collected over 20 years on the Isle of May (Scotland) using a pool of individuals marked as adults. Because the years of hatching of individuals were not known, we used the time (years) elapsed since first capture (TFC) as a measure of age. The use of this proxy did not create any bias in estimating senescence in the case of a linear decline, nor did it greatly decrease the power of a test for senescence. Breeding success declined significantly from 0.81 (95% CI: 0.77–0.84) to 0.62 (0.54–0.68) over the study period. It also varied in relation to age, initially increasing (from 0.62 (0.54–0.68) at TFC of 0 year to 0.76 (0.73–0.79) at TFC of 9 years) up to a plateau (from TFC of 9 years with 0.76 (0.73–0.79) until TFC of 13 years with 0.77 (0.74–0.79) before declining in later life to 0.70 (0.61–0.78) at TFC of 19 years). Survival was generally high and varied significantly from year to year. It also declined with TFC: survival of birds marked in 1982 decreased from 0.92 (0.85–0.96) at a TFC of 0 year to 0.88 (0.82–0.92) at a TFC of 19 years. Resighting probabilities also declined with TFC suggesting that the oldest birds do not come back to the colony to breed as regularly as younger individuals. These findings indicate that individual common guillemots on the Isle of May showed both actuarial and reproductive senescence.
Many studies have suggested that reproductive performance improves during the pair-bond, which might explain why individuals remate with the same partner in many species. However, discussion exists about whether the association between reproductive performance and pair-bond duration that is reported in these studies reflects a causal relationship. Usually it is unclear whether a positive association is caused by pairs improving during their pair-bond or by high-quality pairs staying together for longer. Furthermore, reproductive performance often also depends on the age or breeding experience of parents, which all covary with pair-bond duration. A much needed experimental approach is lacking so far. We investigated the effect of pair-bond duration on reproductive performance in a long-lived monogamous bird species based on natural as well as experimental variation. The duration of oystercatcher (Haematopus ostralegus) pair-bonds, which were followed for 21 years, strongly affected reproductive output, even after controlling for effects of age and breeding experience. Pairs improved during their pair-bond, and there were no indications of selective disappearance of low-quality pairs; however, pairs that stayed together for very long performed badly. Experimental removal of one partner showed that the reproductive cost of divorce depended on the pair-bond duration with the old partner. In addition, after remating, the newly formed pairs strongly improved again, independent of the age and breeding experience of the remated pair members. As such, this study provides the first experimental evidence of a causal effect of pair-bond duration on reproductive performance. Copyright 2006.
SYNOPSIS. The majority of bird species exhibit age-dependent survival and reproduction. In almost all cases, first time breeders or young individuals perform at a lower and slower rate than older individuals. This review highlights the importance of age-dependent effects and urges further study of the proximate and ultimate mechanisms involved. Age effects show substantive variation across life history stage, breeding season, year, cohort, habitat types and environmental conditions both within and across taxons. In some populations or years, age effects disappear. Despite the variable patterns, age effects show amazing persistence in a variety of extreme ecological and environmental conditions. Experimental manipulations of food, predation pressure and breeding experience do not usually remove age effects. Age-dependent effects may be maintained or accumulate through the breeding season and profoundly influence fitness, or they may be washed out or reversed by events later in the breeding season. Recently, we have amassed substantive information about the patterns of variation in age-dependent reproduction and survival among individuals, but we have made little progress toward understanding the proximate mechanisms responsible for this variation. Proximate and ultimate processes are inextricably linked, and thus the study of age-dependence is highly relevant to the further development of life history theory. Studies of age-dependent performance have general relevance to population management and conservation issues as age sub-structuring may contribute substantially to annual or inter-populational variation in reproductive success.
Variables related to fecundity or reproductive success like clutch size, egg size, chick growth and survival, etc., are subject to seasonal declines in numerous species of seabirds breeding in temperate or polar areas. Several hypotheses have been proposed to explain this phenomenon: 1) food availability decreases throughout the breeding season (food supply hypothesis); 2) late nests suffer higher predation risks due to the diminishing dilution effect (predation hypothesis); 3) young or inexperienced breeders, or individuals less efficient in finding food, will breed late (parental quality hypothesis), and 4) late reproducers do not invest as much as early ones (reproductive restraint hypothesis) because a) chicks hatched late in the season have a lower reproductive value, and/or b) an increasing need to invest in the adults' own survival as the season advances. Here, I elucidate the generality of seasonal declines in fecundity or breeding success in seabirds. Further, the impact of age and breeding experience on reproductive performance is shown to be important, as predicted by the 'parental quality' hypothesis. A search of the seabird literature shows scant evidence on the importance of seasonal trends in food availability or predation risk for eggs and chicks. Further, the basic tenets of the 'restraint' hypothesis are discussed in full and its underpinnings in life-history theory formally presented. This hypothesis has not received its due share of attention in the seabird literature, although it appears especially suitable for such long-lived animals. Finally, the scarce experimental evidence testing the different hypotheses is fully reviewed. Several experiments are shown to be flawed in their design and statistical analysis. The two clearest experiments do not support the 'parental quality' hypothesis, and in one case are in accordance with the 'restraint' hypothesis. There is an urgent need for further experimental work.
We studied the breeding performance of very old Common Terns (Sterna hirundo) at Bird Island, USA (41°40′N, 70°43′W), in 1999. We studied birds aged ≥18 yr, comprising the oldest 5% of the birds breeding at this site. We located 24 of these old birds and measured their breeding performance, including laying dates, clutch sizes, egg masses, hatching success, chick growth, chick survival, and overall productivity. We compared their performance with that of several reference groups, including a date-matched group of young birds aged 6-9 yr and date-matched birds of all ages. Breeding performance declined with laying date in all groups. The old birds were more successful in raising chicks than any of the reference groups. Within the group of old birds, breeding performance remained high or improved with age, even after controlling for effects of laying date. Males and females were represented equally among the group of old birds; there was no evidence that performance was higher among old males or old females. If the Common Terns at this site experience any senescent decline in breeding performance within their 20-25 yr lifespan, this must be offset either by increased reproductive effort or by selective survival of high quality individuals.
1. A substantial correlation exists between the breeding ages of short-tailed shear-waters in pair-bonds. 2. Much of this correlation can be explained by prolonged pair-bonds between the same mates, and the predominant availability of unpaired, inexperienced birds. 3. Using Monte Carlo simulation, a comparison of the differences in age observed between pair members with those produced assuming random pairing of available birds, indicated some weak assortative mating on the basis of breeding age. 4. The probability of breeding success depended both upon the breeding ages of the partners and upon the length of time they had bred together; the latter appeared the stronger effect. 5. In the first year of a pair-bond, the breeding age of the female had a much stronger effect than that of the male in determining the probability of reproductive success.
Colony size increased from 4 birds in 1949 until 1965, declined through to 1977, increased again until 1981 but declined in 1982. At its peak, the colony contained 105 breeding pairs. Breeding birds returned to the NE England colony slightly later from 1955 until 1963. This was followed by progressively earlier return until 1978 but more recently, return has become later again. Laying date changed little until 1976, then became progressively later each year. Clutch size increased until 1960, then declined by c10% to 1982. Egg volume and the growth rate of chicks have remained constant. Hatching success of eggs, fledging success of chicks and the number of chicks fledged per pair all initially increased then progressively declined (by 15%, 14% and over 27% respectively). All have recently recovered slightly. The survival rates of breeding females declined during 1966-69 and remained at the new level. The survival rates of males declined for a longer period before recovering slightly. Male and female survival rates deviated markedly from each other in 1954-66 and 1970-78. During the latter period a number of incidences of bigamy and female-female pairs were recorded suggesting that there was a shortage of males recruiting to the colony. In years of higher than average mortality, the 'divorce' rates amongst the surviving pairs were also higher. The early, small changes were probably associated with the changing age structure within the new colony, whereas recent declines probably result from changes in food availability.-from Authors
The condition, breeding performance and survival of the wandering albatross Diomedea exulans were studied in relation to the bird's reproductive experience and age. In both sexes, the body weight of immature birds increased steadily with age from 4 to 7 yr. In individual immature females it increased from one season to the next, and only those attaining a threshold value bred, irrespective of their age. At similar ages immature birds tended to be lighter than breeders. The weight of breeding males increased progressively throughout the breeding life, while that of females increased only during the first 15 yr. In contrast to most species the date of laying for first time breeders was earlier than for experienced birds. Experienced birds tended to lay at similar dates from one breeding season to the other. Birds failing to breed during the previous breeding season tended to lay earlier than successful individuals. The size of the egg and breeding success increased with the age and experience of the female to a maximum at 17-20 yr or 5-7 breeding attempts and then decreased in the older or more experienced birds. For first time breeders the breeding success and rate of return was the same for older individuals as for younger. The proportion of birds breeding one year after a failed breeding season was lower in birds breeding for the first time than in more experienced birds. There was no significant difference between the proportion of inexperienced and experienced birds returning to breed two yr after a successful breeding season. Birds with more than eight yr breeding experience also tended to postpone their return after a failed season longer than less experienced birds. Annual survival rate did not vary significantly with age between 4 and 22 yr. Birds older than 27 yr had a significantly lower survival than birds aged 16-22 yr (92.9% compared to 97.2%). This study suggests that in a very long-lived bird like the wandering albatross survival is not influenced by reproduction, particularly in the early ages because the onset of breeding is delayed until the risk of an increased mortality at first breeding has disappeared. Condition has probably an important influence in the decision to breed. The age related changes in breeding performance, condition and survival observed in the wandering albatross are probably influenced by the cumulative effects of an increase in skill and thereafter reproductive restraint at young ages, by the selection of high quality birds at intermediate ages and by senescence at older ages.
Excluding age and experience effects, individual quality is frequently assumed to be a fixed trait. This paper tests whether an individual's apparent quality, as indicated by its timing of breeding, is indeed permanent. This is assessed by studying the repeatability of laying dates of a long-lived seabird, the great skua Catharacta skua. Laying date is known to be an important component of fitness in many seabirds, including great skuas. Mathematical models were constructed to evaluate the effect of age-specific timing of breeding on repeatability estimates. Simulations show that, in short-term studies (lasting 2 or 3 years), age-specific laying dates can produce spurious repeatabilities with values ranging between 0.1 and 0.2, when the value should be zero. Field observations showed that individual consistency of timing of breeding was high over short time intervals, but disappeared over longer periods (4 or 5 years). A comparison between field data and the simulations demonstrated that the observed high repeatabilities in consecutive years, and the fast subsequent declines, cannot be fully accounted for by age effects. The mechanisms underlying this surprising pattern are completely unknown, but results clearly suggest that apparent individual quality is a transient attribute in these birds.
The proportion of eggs that produced free-flying young increased with increasing breeding experience from an initial 0.4-0.45 to a maximum of 0.75-0.8, before falling to 0.55-0.65 in the most experienced birds. Overall, 10-11% of breeding shearwaters were absent, and 15-18% were present but not recorded with an egg, in any year. Both absentee and non-laying rates declined with increasing age. Older 1st-breeding birds had a higher initial reproductive success than those starting younger. Thereafter, there were no consistent differences in reproductive rates related to age of 1st breeding. Individuals that lived for longer had a higher reproductive success, on average, than shorter-lived birds, especially early in their reproductive careers. -from Authors
Over 8,000 Little Penguins have been banded as chicks in Australia, mainly in the south-east. There have been 201 recoveries of dead birds away from the banding place besides numerous live records at the banding site and elsewhere. The young disperse rapidly after leaving their natal colony, with a strong tendency to move westward from Phillip Island, Victoria, the colony for which there is most information, particularly favouring an area centred on Cape Otway. Birds banded in New South Wales disperse northward and southward along the coast reaching as far as Tasmania in the south and Port Phillip Bay in the south and west. Some young birds return to their natal colonies to moult when one and two years old but their whereabouts in the intervals we not known. Some birds subsequently breed at their natal colony, others moult or breed or do both elsewhere. Survival after banding is influenced by the weight of the chicks at the time of fledging and whether they were raised early or late in the season.
This study of breeding Blue Penguins Eudyptula minor minor was undertaken in south-eastem New Zealand during 1982/83 and enabled quantitative analyses and comparisons of nestling growth rates of morphometric characters. Comparisons both within and between subspecies were used to assess the degree of variation in growth rates and breeding success. The logistic growth model best described E. minor growth with feet showing most rapid growth, followed by weight, flipper and bill respectively. It is suggested that the reason for rapid growth rates of feet and flippers in penguins is the necessity to maintain thermal balance. The subspecies of E. minor showed positive correlations between latitude and both asymptotic and adult weight and an inverse relationship between growth rate and asymptotic weight, but rates of increase in weight were not correlated with latitude. In th~s study E. m. minor experienced a fledging success of 75% but an egg success of only 47%. After comparison of reproductive performance in other subspecies, years and locations, it is suggested that brood reduction occurs in response to unfavourable conditions. In populations where extensive brood reduction occurred, the mean growth rates of E. minor nestlings were more rapid than in populations that experienced only limited reduction of broods.
The Little Penguin Eudyptula minor has been studied at Phillip Island, Vic., for nine seasons. The mean annual survival rate of breeding adults is estimated at 85.8 per cent, giving a mortality rate of 14.2 per cent per annum and a life expectancy of 6.5 years. Estimates for males and for females do not differ significantly. Birds that moved from the study area after breeding once have not been taken into account. Places, times and causes of mortality are given, where known.
Little Penguins were studied in the main breeding colony at Phillip Island, Victoria, on weekly and, later, monthly visits during eleven years. The birds were present all the year but numbers built up towards the onset of the breeding season, showing a three-week cycle of attendance. Breeding numbers varied slightly from year to year with a more marked drop in 1978 and perhaps 1973. The timing of breeding also differed from year to year, varying within a year and from year to year much more than in other seabirds of temperate latitudes. Study of breeding success showed that on average August to November each produced about the same number of young, though in any one year these could be differences between these months. There were individual differences in breeding efficiency associated with the length of time a bird was recorded in the area. These reflected differences in in- dividual 'quality' rather than in age or experience. Pair bonding and divorce are described. Birds that had bred before and changed mates nested earlier in the next season than they did in the previous season with the old mate. Failure to breed by adults was exceptional but may occur in some years. Few birds banded as chicks have been found breeding but those that have have apparently been at least three or four years old. There were some marked differences between the breeding of the species at Phillip Island and in Tasmania. Various features of the breeding of the Little Penguin are considered from the point of view of strategies to enhance reproductive success: choice of burrow, size of clutch, age of first breeding, pattern of pair bonding, timing of the breeding season. Regarding the last, the population on Phillip Island is intermediate between 'typical' penguins of polar and sub-polar regions and those of some of the tropical genus Spheniscus, which show opportunistic breeding throughout the year.
This paper reports on the seasonal timing of moult and the location of the moulting place in relation to the breeding burrow at Phillip Island. Some individuals moulted in burrows close to where they breed, sometimes in the identical burrow. The birds were more likely to use the same burrow or remain in the vicinity when the breeding had been successful. Some moulting birds changed burrows, and this may be commoner in some colonies in some years. The date of moult appeared relatively constant from year to year compared with egglaying. Slight differences in the date were evident between colonies at Phillip Island, Victoria, Tasmania and New Zealand.
A long-term study of marked individuals in a numerically stable Sparrowhawk breeding population enabled the reproductive and survival rates of females of different ages to be calculated. These estimates were then used to calculate reproductive value, the mean number of young produced by females of different ages during the rest of their lives. The data provided evidence, not only for improvement in survival and breeding success in the early years of life, but also for senescence, i.e., a deterioration in survival and breeding success later in life. Average annual survival increased from 0.49 in 1st-yr females to 0.66 in 4 yr olds, and declined to 0.28 in 9 yr olds (maximum life-span 10 yr). Average annual production of young increased from 0.3 in 1st-yr females (including nonbreeders) to 3.3 in 5 yr olds, and declined to 1.8 in 9 yr olds. Mean reproductive value increased from 3.1 in 1st-yr females (including nonbreeders) to 8.1 in 4 yr olds, and declined to 2.1 in 9 yr olds.
Heterogeneity in individual quality can be a major obstacle when interpreting age-specific variation in life-history traits. Heterogeneity is likely to lead to within-generation selection, and patterns observed at the population level may result from the combination of hidden patterns specific to subpopulations. Population-level patterns are not relevant to hypotheses concerning the evolution of age-specific reproductive strategies if they differ from patterns at the individual level. We addressed the influence of age and a variable used as a surrogate of quality (yearly reproductive state) on survival and breeding probability in the kittiwake. We found evidence of an effect of age and quality on both demographic parameters. Patterns observed in breeders are consistent with the selection hypothesis, which predicts age-related increases in survival and traits positively correlated with survival. Our results also reveal unexpected age effects specific to subgroups: the influence of age on survival and future breeding probability is not the same in nonbreeders and breeders. These patterns are observed in higher-quality breeding habitats, where the influence of extrinsic factors on breeding state is the weakest. Moreover, there is slight evidence of an influence of sex on breeding probability (not on survival), but the same overall pattern is observed in both sexes. Our results support the hypothesis that age-related variation in demographic parameters observed at the population level is partly shaped by heterogeneity among individuals. They also suggest processes specific to subpopulations. Recent theoretical developments lay emphasis on integration of sources of heterogeneity in optimization models to account for apparently “sub-optimal” empirical patterns. Incorporation of sources of heterogeneity is also the key to investigation of age-related reproductive strategies in heterogeneous populations. Thwarting “heterogeneity's ruses” has become a major challenge: for detecting and understanding natural processes, and a constructive confrontation between empirical and theoretical studies.