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Survival of female White-cheeked Pintails during brood rearing in Puerto Rico
Abstract
Anas bahamensis (White-cheeked Pintail) is widely distributed across the Caribbean
islands and South America. The species is classified as threatened in Puerto Rico and
a species of least concern across most of its range. Little demographic data exist for the
species, particularly during the breeding season. During 2000–2002, we radiomarked 31
incubating females at the Humacao Nature Reserve (Humacao) in southeastern Puerto Rico and estimated daily and interval survival rates of females during brood rearing. Only one of 31 birds died; the average ± 95% CI daily survival rate of pintails was 0.998 ± 0.989–0.999 for all years, and interval survival was 0.913 ± 0.527–0.987 for a 60-day brood-rearing period. High survival of females suggests their mortality during brood rearing does not influence White-cheeked Pintail populations at Humacao, but further studies of reproductive and annual ecology are needed.
... The Humacao Nature Reserve (hereafter, Humacao) in Puerto Rico, nearby islands of Culebra and Vieques, and the Virgin Islands are key habitats for White-cheeked Pintails in the eastern Caribbean region (Collazo and Bonilla-Martínez 2001). Previous research has addressed nesting ecology, annual survival rates, density and population size, and adult movements of these ducks at Humacao and other coastal systems (López-Flores et al. 2014). López-Flores et al. (2014) quantified survival of brood-rearing White-cheeked Pintail females. ...
... Previous research has addressed nesting ecology, annual survival rates, density and population size, and adult movements of these ducks at Humacao and other coastal systems (López-Flores et al. 2014). López-Flores et al. (2014) quantified survival of brood-rearing White-cheeked Pintail females. They documented a high hen survival rate suggesting that adult female survival was not a bottleneck to recruitment at Humacao. ...
... We used a dip net (~0.6 m) with a pole (~1.5 m) to capture nesting female White-cheeked Pintails in artificial structures or natural vegetation~1 week before predicted hatching date. We radio-tagged females with prong-andsuture style VHF transmitter (Model 2032, Advanced Telemetry Systems, Isanti, Minnesota, USA) and returned them to the nest (Rotella and Ratti 1992; see also López-Flores 2005, López-Flores et al. 2014. During the 2000 pilot season, we only marked nesting females in June and July, while in 2001 and 2002 we marked and tracked birds from March through mid-late August. ...
Duckling survival is an important influence on recruitment in several North American Anas species. White-cheeked Pintail (Anas bahamensis) breeding in Puerto Rico encounter a variety of wetland types that may influence duckling survival. We monitored fates of 92 radio-tagged ducklings in 31 broods in 5 wetland habitat types at Humacao Nature Reserve in southeastern Puerto Rico from 2000 to 2002. Wetlands included 2 separate coastal lagoon complexes, mangrove forest, and managed and unmanaged wetland impoundments containing herbaceous vegetation. We used known-fate models to estimate daily and interval survival rates of ducklings and broods. We conducted conservative and liberal analyses of survival because of uncertain fates of 36 ducklings. In the conservative analysis, the most parsimonious model for duckling survival contained wetland type and a positive influence of daily precipitation. In the liberal analysis, duckling survival also varied among wetlands, was positively influenced by daily precipitation, but negatively influenced by hatch date. Brood survival was also positively influenced by precipitation and female body mass. Managed wetland impoundments and shallowly flooded lagoon habitats containing ferns, interspersed cattail (Typha dominguensis), and other herbaceous cover promoted up to 3 times higher survival of ducklings over the course of a 30-day duckling period than we found in mangroves, more deeply flooded lagoons with predominately restricted shoreline cover, or unmanaged impoundments overgrown with vegetation. Broad confidence intervals for survival estimates among wetlands preclude unequivocal interpretation, but our results suggest that White-cheeked Pintail ducklings survive poorly in mangroves but benefit from appropriate management.
We estimated numbers and survival of White-cheeked Pintails (Anas bahamensis) in eastern Puerto Rico during 1996-1999. We also quantified their movements between Culebra Island and the Humacao Wildlife Refuge, Puerto Rico. Mark-resight population size estimates averaged 1020 pintails during nine, 3-month sampling periods from January 1997 to June 1999. On average, minimum regional counts were 38 % lower than mark-resight estimates (mean = 631). Adult survival was 0.51 ± 0.09 (SE). This estimate is similar for other anatids of similar size but broader geographic distribution. The probability of pintails surviving and staying in Humacao was hiher (67 %) than for counterparts on Culebra (31 %). The probability of surviving and moving from Culebra to Humacao (41 %) was higher than from Humacao to Culebra (20 %). These findings, and available information on reproduction, indicate that the Humacao Wildlife Refuge refuge has an important role in the regional demography of pintails. Our findings on population numbers and regional survival are encouraging, given concerns about the species' status due to habitat loss and hunting. However, our outlook for the species is tempered by the remaining gaps in the population dynamics of pintails; for examples, survival estimates of broods and fledglings (age 0-1) are needed for a comprehensive status assessment. Until additional data are obtianed, White-cheeked Pintails should continue to be protectd from hunting in Puerto Rico.
I studied the breeding chronology, courtship activities, pair-bond relationships, and parental-care behavior of a sedentary population of White-cheeked Pintails (Anas bahamensis bahamensis) in the Bahamas from 1985 to 1987. The timing and duration of breeding seasons was variable and associated with variation in the onset and amount of winter and spring rainfall. Year-around courtship, mate switches, courtship of brood females, and the formation of extrapair liaisons all reflected intense and continuous competition for quality mates. Most White-cheeked Pintails paired monogamously, but a low level of polygyny occurred regularly: each year, 4 to 9% of paired males had two mates during the breeding season, despite a strongly skewed sex ratio in favor of males (1.45:1). Polygynous males were particularly effective at guarding their mates during the breeding season, an important determinant of female breeding success. The term "male-quality polygyny" is proposed to characterize this form of polygyny. Both long-term pair bonds and mate changes between years were recorded: 10 of 23 marked pairs (43%) stayed together for two or more breeding seasons, while 13 pairs (57%) divorced. Mate retention in the second year was not related to breeding success in the first year. Only females provided parental care, but some males continued to escort and guard their mate for at least part of the brood-rearing period. Although highly variable, male attendance declined with both hatch date and duckling age. Some birds associated as pairs year around, and several pairs stayed together during the wing molt. The sedentary lifestyle in this subtropical climate and the potential for variable and extended breeding seasons appear to be the key ecological factors influencing the complex and variable mating system of this species.
The effort expended on reproduction may entail future costs, such as reduced survival or fecundity, and these costs can have an important influence on life-history optimization. For birds with precocial offspring, hypothesized costs of reproduction have typically emphasized nutritional and energetic investments in egg formation and incubation. We measured seasonal survival of 3856 radio-marked female Mallards (Anas platyrhynchos) from arrival on the breeding grounds through brood-rearing or cessation of breeding. There was a 2.5-fold direct increase in mortality risk associated with incubating nests in terrestrial habitats, whereas during brood-rearing when breeding females occupy aquatic habitats, mortality risk reached seasonal lows. Mortality risk also varied with calendar date and was highest during periods when large numbers of Mallards were nesting, suggesting that prey-switching behaviors by common predators may exacerbate risks to adults in all breeding stages. Although prior investments in egg
The white-cheeked pintail (Anas bahamensis) is listed as threatened, and survey data are needed to assess population status, estimate trends, and guide management on Puerto Rico and territorial islands. We surveyed 51 points in 29 wetland sites to estimate density and population size after the peak of reproduction (Mar-Jul) and before the waterfowl hunting season (Nov-Jan). Estimated density was 2.33 individuals/ha (SE = 0.27), and estimated population size was 3,755 individuals (SE = 435, log-normal 95% CI = 2,995 to 4,708) in 1,614 ha surveyed in August-October 2003-2005. Density differed between August-October 2003 (Ď = 3.07 individuals/ha, SE = 0.41) and 2004 (Ď = 1.26 individuals/ha, SE = 0.17) and between August-October 2004 and 2005 (Ď = 2.54 individuals/ha, SE = 0.47) but not between August- October 2003 and 2005. Spatial distribution ranged from nearly random (estimate of dispersion parameter [b̌] = 0.99) to highly clumped (b̌ = 3.71). We suggest that spatiotemporal variation of wetland hydrochemical conditions caused changes in foraging resources, which in turn caused changes in white-cheeked pintail density and spacing patterns. We recommend surveying 186 points 3 times in August-October for estimated density to have a coefficient of variation of 0.10, even when white-cheeked pintails are highly clustered (estimate of exp cluster size, Ě[s] = 16.1, SE = 2.8) and clumped (b = 4) in space. We provide additional recommendations for integrating monitoring, research, and management objectives to better understand the ecology and promote the conservation of white-cheeked pintails and their habitats locally and regionally.
The wide range in incubation periods among bird species has puzzled biologists for decades, because an extended egg‐phase increases time‐dependent mortality of the eggs.
We investigated a recently proposed mechanistic explanation inspired by life‐history theory, suggesting that adults may increase their own survival by reducing nest attentiveness, the percentage of daytime spent incubating eggs, in exchange for reduced offspring (egg) survival due to a longer incubation period. Incubation behaviour and egg temperatures ( T egg ) of 14 bird species in the humid lowland tropics were studied to test the hypothesis that lower nest attentiveness and reduced T egg cause longer incubation periods.
Increased nest attentiveness correlated with higher average T egg . However, neither nest attentiveness nor average T egg was associated with the length of the incubation period. Longer off‐bouts resulted in lower T egg , but neither number of off‐bouts nor off‐bout length was associated with incubation period. In addition, we reanalysed a previously published negative association between T egg and incubation period based on literature data from temperate passerine birds using a larger data set and found no significant correlation.
In conclusion, our results do not support the hypothesis that longer incubation periods are caused by reduced nest attentiveness and corresponding lower T egg .
Research on the impacts of house mice Mus musculus introduced to islands is patchy across most of the species’ global range, except on islands of the Southern Ocean. Here we
review mouse impacts on Southern Ocean islands’ plants, invertebrates, land birds and seabirds, and describe the kinds of
effects that can be expected elsewhere. A key finding is that where mice occur as part of a complex of invasive mammals, especially
other rodents, their densities appear to be suppressed and rat-like impacts have not been reported. Where mice are the only
introduced mammal, a greater range of native biota is impacted and the impacts are most severe, and include the only examples
of predation on seabird eggs and chicks. Thus mice can have devastating, irreversible and ecosystem-changing effects on islands,
impacts typically associated with introduced rats Rattus spp. Island restoration projects should routinely include mouse eradication or manage mouse impacts.
Estimates of juvenile survival from hatch to fledging provide important information on waterfowl productivity. We develop a model for estimating survival of young waterfowl from hatch to fledging. Our model enables interchange of individuals among broods and relaxes the assumption that individuals within broods have independent survival probabilities. The model requires repeated observations of individually identifiable adults and their offspring that are not individually identifiable. A modified Kaplan-Meier procedure (Pollock et al. 1989a,b) and a modified Mayfield procedure (Mayfield 1961, 1975; Johnson 1979) can be used under this general modeling framework, and survival rates and corresponding variances of the point estimators can be determined.
We developed a technique for attaching transmitters to newly hatched mallard (Anas platyrhynchos) ducklings. Transmitters remained attached from hatching to fledging with no effect on growth, development, or survival. The technique is potentially applicable to the precocial young of many other species of birds.
Knowledge of survival of female ducks is important for understanding population dynamics and managing hunted species. We estimated survival of female wood ducks (Aix sponsa) during brood rearing in different wetland environments in Mississippi (1996-1999) and Alabama (1998-1999). Survival was 0.90 ± 0.05 (Ŝ ± SE) in Mississippi and 0.92 ± 0.07 in Alabama. A composite estimate of female survival for all years and both areas was 0.90 ± 0.04. High survival of females during brood rearing in our study areas suggests that this factor may be less important than other population factors (e.g., duckling survival) influencing fall recruitment in these wood duck populations.
Seasonal survival of 109 adult female mallards (Anas platyrhynchos) fitted with radio transmitters was evaluated in northcentral Minnesota during 1968-74. Survival rates for the 169-day breeding and postbreeding period were: 1.0 during nest initiation (36 days), 0.798 during incubation (28 days), 0.943 during brood rearing (51 days), 0.947 during molt (26 days), and 1.0 during premigration (28 days). Survival for the 169-day spring-summer period was 0.713 for adult females remaining on the study area. Fall-winter survival was estimated at 0.881 for those adult birds remaining on the study area throughout the summer. The data confirm speculation on relative risk to females of various phases of the mallard reproductive cycle and support previous conclusions that the northcentral Minnesota breeding mallard population is not self sustaining. The value of learning further details of processes affecting specific seasonal mortality factors for both adult and young waterfowl is emphasized.
We present results on the estimation of survival distributions for an important problem in animal ecology. The problem involves estimation of survival distributions using radio-tagged animals. It requires allowance for censored observations due to radio failure, emigration from the study area, and animals surviving past the end of the study period. We show that survival analysis techniques already used in medical and engineering studies may be applied to this problem. Emphasis is placed on the model assumptions and the need for further research. An example to illustrate the strengths and weakness of this approach is presented.
The estimation of survival distributions for animals which are radio-tagged is an important current problem for animal ecologists. Allowance must be made for censoring due to radio failure, radio loss, emigration from the study area and animals surviving p88l. :~the end of the study period. First we show that the Kaplan-Meier .procedure wid~ly used in medical and engineering studies can be applied to this problem. An example using some quail data is given for illustration. As radios maItunction -or are lost, new radio-tagged animals have to be added to the study. We show how this modification can easily be incorpor~.ted inf.<? the basic Kaplan-Meier procedure. Another example using quail data is used to illustrate the extension. We also show how the log rank test commonly used to compare two survival distributions can be generalized to allow for additions. Simple computer programs which can be run on a PC are available from the authors.
Renesting is an important strategy for coping with nest loss in many species of birds. We investigated renesting behavior of radiomarked Mallards (Anas platyrhynchos) breeding in the Canadian Prairie Parklands and found that females were persistent renesters, replacing >57% of 4,112 destroyed nests. Renesting propensity was most affected by nest initiation date, with ∼90% of unsuccessful females renesting if destroyed clutches had been initiated in April but <10% renesting for clutches initiated after 20 June. Probability of renesting declined with successive number of nesting attempts, but this was primarily an effect of initiation date. Renesting propensity increased with female age and body condition and declined for birds that had invested more time tending their previous clutch, but the latter effect was pronounced only among late-nesting females. The amount of time required to produce a replacement clutch was primarily a function of whether females were engaged in rapid follicle growth when nest failure occurred: 44% of females (383 of 870) that lost nests during early laying renested within 4 days, whereas only 2% (12 of 639) that lost nests after clutch completion renested within 4 days. Although clutch size was smaller in renests, this was entirely an artifact of later laying dates. Our results suggest that seasonal timing had the most influence on renesting behavior. Female age, body condition, and prior nesting effort had smaller, but demonstrable, influence.
Relationships between vital rates and population growth rate (lambda) are critical to understanding and managing population dynamics. Considerable study of the midcontinent mallard (Anas platyrhynchos) population has been directed to understanding how vital rates respond to environmental fluctuations and management, but. inference to the relative importance of specific vital rates to gamma remains weak. We used analytic and simulation-based sensitivity analyses of a stage-based matrix model of female midcontinent mallards to compare the relative importance of vital rates to lambda. For each vital rate, we estimated mean values and process variation (biological variation across space and time) for females breeding on sites of approximately 70 km(2) in the Prairie Pothole Region (PPR) of the United States (Montana, North Dakota, South Dakota, Minnesota) and Canada (Saskatchewan, Manitoba, Alberta). We conducted perturbation analyses (i.e., analytic sensitivities and elasticities) to predict the relative influence of changes in vital rates on lambda. We conducted variance decomposition analyses to assess the proportion of spatial and temporal variation in lambda explained by process variation in each vital rate. At mean Values of vital rates, analytic sensitivity of lambda was highest to nest success and survival of adult females during the breeding season and nonbreeding season; hence, equal absolute changes in these vital rates would be predicted to result in the largest Deltalambda relative to other vital rates. Variation in sensitivities and elasticities across process variation in vital rates was primarily explained by variation in nest success and Survival of ducklings. Process variation in breeding parameters was driving variation in lambda: vital rates explaining the most variation were nest Success (43%), survival of adult females during the breeding season (19%), and survival of ducklings (14%). Survival of adult females outside the breeding season accounted for only 9% of variation in lambda. Our analyses suggested that predation processes on the breeding grounds were the primary proximate factors limiting population growth.
There has been widespread speculation that breeding activity places adult female mallards (Anas platyrhynchos) at heightened risk of harvest due to insufficient time to complete the wing molt or recover body condition prior to onset of hunting and autumn migration. We tested the hypotheses that breeding females have higher rates of harvest and reduced prospects for survival by estimating band recovery rates (f) and annual survival (S) in relation to individual measures of breeding effort for 3,055 adult female mallards that had been banded and radiomarked during the breeding season in the Prairie-Parkland Region of Canada, 1993–2000. Birds that had been marked with external prong-and-suture transmitters had lower estimated survival rates (S = 0.518, SE = 0.118) than birds marked with implant transmitters (S = 0.731, SE = 0.061), but rates for birds marked with implant transmitters did not differ from expectations based on other studies for females marked only with legbands. After excluding external transmitters, we found that recovery rates were unaffected by any measures of reproductive effort, but annual survival was lower for females that tended broods to 60 days of age (S = 0.474 ± 0.115) versus females that never hatched a nest (S = 0.654 ± 0.042). Telemetry data indicated that brood-rearing females experienced extremely low mortality, so reduced survival of females that raised broods presumably resulted from insufficient time to molt and prepare for autumn migration. Management efforts that promote successful early nesting attempts may also improve adult female survival by allowing females more time to molt and prepare for autumn migration, whereas hunting regulations designed to protect late-breeding females may prove ineffective if such individuals have higher natural mortality. © 2012 The Wildlife Society.
Although the primary mallard (Anas platyrhynchos) breeding area in North America has been greatly modified by agriculture, the relationship between habitat loss and mallard recruitment is not well understood. Consequently, we used radio telemetry to estimate brood and duckling survival for 69 mallard broods in southwestern Manitoba, 1987-89, and tested for effects of habitat conditions and hatching date. Annual brood and duckling survival averaged 0.49 (range = 0.34-0.70) and 0.22 (range = 0.16-0.26), respectively. Brood survival was greatest (P = 0.09) in the wettest year. Logistic regression analysis indicated (Hosmer-Lemeshow goodness-of-fit Chi-square = 5.16, 8 df, P = 0.74) that brood survival was directly related to wetland density and inversely related to hatching date. Duckling survival was similar (P = 0.13) among years and was greatest (P = 0.01) for ducklings hatched before 19 June in areas with high wetland density. We suggest that management should be directed at promoting early hatching in areas of high wetland density by improving the quality and quantity of nesting cover.
Ecology of mallards (Anas platyrhynchos) breeding in the Lower Great Lakes Region of the United States has not been investigated as comprehensively as mid-continent populations of this species. We studied mallard breeding ecology in the Cowaselon Creek Watershed Area in New York during 2003–2004. Daily and 100-day breeding season survival of female mallards (n = 41) was 0.997 and 0.782, respectively, and was positively influenced by female age and body mass at time of capture. Eight radiomarked female mallards were killed by either mammalian or avian predators. Earliest and latest nest initiation dates were 14 April and 24 May 2003–2004, respectively, and females initiated nests in wetlands 10 days earlier than in uplands. Overall, average clutch size was 9.4 ± 0.32 eggs (SE), and probability of reproductive success of females was 0.27, with nest success in wetlands and uplands of 0.71 and 0.42, respectively. Daily and 35-day nest success was 0.968 and 0.326, respectively. We found an estimated 70% of all initiated nests prior to clutch destruction or hatch; thus, our estimates of nesting and re-nesting effort may be biased low. Survival of breeding females and nest success were comparable or exceeded parameter estimates from other regions of the mallard breeding range. We suggest that wetland and upland habitats are both important to nesting mallards in New York and elsewhere in the Lower Great Lakes Region. © 2013 The Wildlife Society.
Food limitation is generally thought to underlie much of the variation in life history traits of birds. I examined variation and covariation of life history traits of 123 North American Passeriformes and Piciformes in relation to nest sites, nest predation, and foraging sites to examine the possible roles of these ecological factors in life history evolution of birds. Annual fecundity was strongly inversely related to adult survival, even when phylogenetic effects were controlled. Only a little of the variation in fecundity and survival was related to foraging sites, whereas these traits varied strongly among nest sites. Interspecific differences in nest predation were correlated with much of the variation in life history traits among nest sites, although energy trade-offs with covarying traits also may account for some variation. For example, increased nest predation is associated with a shortened nestling period and both are associated with more broods per year, but number of broods is inversely corr
A total of 62 Mallard (Anus platyrhynchos) females were captured at their nests in eastern South Dakota during 1990 and 1991. Females were captured on an island, a peninsula cut off from the mainland by excavation, and a peninsula protected by an electric fence that deters mammals. Loop harnesses were used to attach radio transmitters to females to evaluate possible effects of marking females on survival of their ducklings and to determine the influence of brood rearing on female survival. No difference was found in duckling (P = 0.999) or brood (P = 0.458) (e.g., one or more ducklings alive in brood) survival to 7 d for females marked from 1 d prior to hatch to immediately post hatch (still in nest) compared with those marked at 3-9 d before hatch (P = 0.081). There also were no differences in survival by age class between marked broods that did not suffer total mortality and unmarked broods (P > 0.05). If survival of broods was influenced by harness attachments on females, it likely occurred in females suffering total brood loss early in brood rearing. Marked females with broods had poorer survival to 21 d than marked females that had lost or abandoned their clutches or broods (73.5ø70 vs. 100070, P < 0.001).
Mallard (Anas platyrhynchos) populations in the United States portion of the Great Lakes region increased through the 1990s but have since declined. To promote sustainable growth of this population, managers need to understand how perturbation of vital rates will affect annual population growth rate (Λ). We developed a stage-based model representing the female mallard population in the Great Lakes using vital rates generated from a landscape-level study documenting reproductive parameters from 2001 to 2003. We conducted perturbation analyses (i.e., sensitivity analyses) to identify vital rates that most influence Λ and variance decomposition analyses to determine the proportion of variation in Λ explained by variation in each vital rate. Perturbation analyses indicated that Λ was most sensitive to changes in nonbreeding survival, duckling survival, and nest success. Therefore, changes in these vital rates would be expected to result in the greatest ΔΛ. Process variation in breeding season parameters accounted for 63% of variation in Λ. Breeding season parameters explaining the most variation were duckling survival (32%) and nest success (16%). Survival of adult females outside the breeding season accounted for 36% of variation in Λ. Harvest derivation, high harvest, and high sensitivity of Λ to nonbreeding survival for Great Lakes female mallards suggests there is a strong potential for managing the Great Lakes mallard population via harvest management. Because Λ was highly sensitive to changes in duckling survival, we suggest programs that emphasize wetland protection, enhancement, and restoration as a management strategy to improve population growth for breeding mallards.
Although North American wood ducks (Aix sponsa) are well-studied throughout their range, researchers know little about demographic and environmental factors influencing survival of ducklings and broods, which is necessary information for population management. We studied radiomarked female and duckling wood ducks that used nest boxes and palustrine wetlands at Noxubee National Wildlife Refuge (NNWR) in Mississippi, USA, in 1996–1999, and riverine wetlands of the Tennessee-Tombigbee Rivers and Waterway (TTRW) system in Alabama in 1998–1999. We estimated survival of ducklings and broods and evaluated potentially important predictors of duckling survival, including age and body mass of brood-rearing females, hatch date of ducklings, duckling mass, brood size at nest departure, inter-day travel distance by ducklings, site and habitat use, and daily minimum air temperature and precipitation. At NNWR, survival of 300 radiomarked ducklings ranged from 0.15 (95% CI = 0.04–0.27) to 0.24 (95% CI = 0.13–0.3...
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