[Show abstract][Hide abstract] ABSTRACT: Norwegian Northern Gannet Morus bassanus populations exhibit contrasting trends on a regional scale, with several colony extinctions having occurred in recent decades. In an attempt to understand the ecological drivers of such variability, we tested whether resource availability is a factor limiting the current development of gannetries in the Lofoten/Vesterålen area. Between 2007 and 2010, we recorded arrival and departure times of breeding Northern Gannets from two colonies from regions showing contrasting population growth rates during the past two decades. We also recorded the duration of joint attendances by Northern Gannet parents at the nest, performed opportunistic diet sampling and counted numbers of occupied nests. Finally, we compiled ring recoveries over a 30-year period to assess inter-colony movements. Norwegian Gannet parents spent more time together, attending their chick, and performed shorter foraging trips than those in British and French colonies of similar size. This suggests that, despite some annual variations, their foraging effort was relatively low. Diet samples from both colonies mainly constituted fish of high energetic value, such as large herring Clupea harengus, mackerel Scomber scombrus, and saithe Pollachius virens, prey that are relatively abundant within the study area. Data from ringed birds revealed a northward movement of adults ringed as breeding birds and chicks from extinct Lofoten colonies that established a growing colony close to the North Cape. Recorded foraging features (trip duration, joint attendance and prey quality) during our study does not indicate food availability as a limiting factor explaining successive extinctions and re-colonisations of breeding sites in Lofoten/Vesterålen. White-tailed Eagles Haliaeetus albicilla are known to predate opportunistically on Northern Gannet adults or chicks and their populations are growing in the Lofoten area. Their potential impact on the Norwegian Northern Gannet population dynamics should be further investigated.
Journal of Ornithology 11/2014; · 1.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Conflicts may arise within a moving animal group if its members have different preferred destinations. Many theoretical models suggest that in maintaining group cohesion conflicting preferences can have an overwhelming influence on decision making. However, empirical studies, especially on wild animals, remain limited. Here, we introduce a new study system for investigating collective decision making: king penguins, Aptenodytes patagonicus. Their gregarious lifestyle, the colony's organization into subgroups and group travel make king penguins especially interesting for studying collective movements. Chicks spend their first year of life in groups with other chicks (crèches), and if displaced will return to their crèche. We examined how different levels of navigational conflict affect such homing, by comparing the performance of pairs of chicks from the same crèche with pairs from different crèches. The majority of chicks in both treatments travelled at least part of the journey together; when doing so they were more efficient and faster than individuals travelling alone. Chicks took turns in leading and following. Chicks with a common destination (same-crèche pairs) were more precise at homing and less likely to split up than those with a conflict over preferred destinations (different-crèche pairs). Our results support some, but not all, predictions derived from theoretical models.
[Show abstract][Hide abstract] ABSTRACT: This article is part of a Special Issue ("Chemosignals and Reproduction"). Chemical cues were probably the first cues ever used to communicate and are still ubiquitous among living organisms. Birds have long been considered an exception: it was believed that birds were anosmic and relied on their acute visual and acoustic capabilities. Birds are however excellent smellers and use odors in various contexts including food searching, orientation, but also breeding. Successful reproduction in most vertebrates involves the exchange of complex social signals between partners. The first evidence for a role of olfaction in reproductive contexts in birds only dates back to the seventies, when ducks were shown to require a functional sense of smell to express normal sexual behaviors. Nowadays, even if the interest for olfaction in birds has largely increased, the role that bodily odors play in reproduction still remains largely understudied. The few available studies however suggest that olfaction is involved in many reproductive stages. Odors have been shown to influence the choice and synchronization of partners, the choice of nest-building material or the care for the eggs and offspring. How this chemical information is translated at the physiological level mostly remain to be described, although available evidence suggests that, as in mammals, key reproductive brain areas like the medial preoptic nucleus are activated by relevant olfactory signals. Olfaction in birds receives increasing attention and novel findings are continuously published, but many exciting discoveries are still ahead of us, and could make birds one of the animal classes with the largest panel of developed senses ever described.
Hormones and Behavior 06/2014; · 4.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Many procellariiforms use olfactory cues to locate food patches over the seemingly featureless ocean surface. In particular, some of them are able to detect and are attracted by dimethylsulfide (DMS), a volatile compound naturally occurring over worldwide oceans in correspondence with productive feeding areas. However, current knowledge is restricted to sub-Antarctic species, and to only one study realized under natural conditions at sea. Here, for the first time, we investigated the response to DMS in parallel in two different environments in temperate waters, the Atlantic Ocean and the Mediterranean Sea, employing Cory's (Calonectris borealis) and Scopoli's shearwaters (Calonectris diomedea) as models. To test whether these birds can detect and respond to DMS, we presented them with this substance in a Y-maze. Then, to determine if they use this molecule in natural conditions, we tested the response to DMS at sea. The number of birds that chose the DMS in the Y-maze and that were recruited at DMS-scented slicks at sea suggest that these shearwaters are attracted to DMS in both non-foraging and natural contexts. Our findings show that the use of DMS as a foraging cue may be a strategy used by procellariiforms across oceans but that regional differences may exist, giving a worldwide perspective to previous hypotheses concerning the use of DMS as chemical cue.
Journal of Experimental Biology 02/2014; · 3.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Norwegian Northern Gannet Morus bassanus populations exhibit contrasted trends at a regional scale and several colony extinctions occurred in recent decades. In an attempt to understand the ecological drivers of such variability, we tested whether resource availability is a factor limiting the current development of gannetries in the Lofoten/Vesterålen area. Between 2007 and 2010, we recorded arrival and departure
times of breeding gannets from two colonies from regions showing contrasting population growth rates during the past two decades. We also recorded the duration of joint attendances by gannet parents at the nest, performed opportunistic diet sampling and counted numbers of occupied nests. Finally, we compiled ring recoveries over a 30-year period to assess inter-colony movements. Norwegian gannet parents spent
more time together, attending their chick, and performed shorter foraging trips than those in British and French colonies of similar size. This suggests that, despite some annual variations, their foraging effort was relatively low. Diet samples from both colonies mainly constituted fish of high energetic value, such as large herring Clupea harengus and mackerel Scomber scombrus, and saithe Pollachius virens, prey that are relatively abundant within the study area. Data from ringed birds revealed a northward movement of adults ringed as breeding birds and chicks from extinct Lofoten colonies that established in a growing colony close to the North Cape. Recorded foraging features (trip duration, joint attendance and prey quality) during our study does not indicate food availability as a limiting factor explaining successive extinctions and recolonisations
of breeding sites in Lofoten/Vesterålen. White-tailed eagles Haliaeetus albicilla are known to predate opportunistically on Northern Gannet adult or chicks and their populations are growing in the Lofoten area. Their potential impact on the Norwegian Northern Gannet population dynamics should be further investigated.
Journal of Ornithology 01/2014; · 1.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dynamic soaring is a small-scale flight manoeuvre which is the basis for the extreme flight performance of albatrosses and other large seabirds to travel huge distances in sustained non-flapping flight. As experimental data with sufficient resolution of th ese small-scale movements are not available, knowledge is lacking about dynamic soaring and the physical mechanism of the energy gain of the bird from the wind. With new in-house developments of GPS logging units for recording raw phase observations and of a dedicated mathematical method for postprocessing these measurements, it was possible to determine the small-scale flight manoeuvre with the required high precision. Experimental results from tracking 16 wandering albatrosses (Diomedea exulans) in the southern Indian Ocean show the characteristic pattern of dynamic soaring. This pattern consists of four flight phases comprising a windward climb, an upper curve, a leeward descent and a lower curve, which are continually repeated. It is shown that the primary energy gain from the shear wind is attained in the upper curve where the bird changes the flight direction from windward to leeward. As a result, the upper curve is the characteristic flight phase of dynamic soaring for achieving the energy gain necessary for sustained non-flapping flight.
[Show abstract][Hide abstract] ABSTRACT: Pelagic birds, which wander in the open sea most of the year and often nest on small remote oceanic islands, are able to pinpoint their breeding colony even within an apparently featureless environment, such as the open ocean. The mechanisms underlying their surprising navigational performance are still unknown. In order to investigate the nature of the cues exploited for oceanic navigation, Cory's shearwaters, Calonectris borealis, nesting in the Azores were displaced and released in open ocean at about 800 km from their colony, after being subjected to sensory manipulation. While magnetically disturbed shearwaters showed unaltered navigational performance and behaved similarly to unmanipulated control birds, the shearwaters deprived of their sense of smell were dramatically impaired in orientation and homing. Our data show that seabirds use olfactory cues not only to find their food but also to navigate over vast distances in the ocean.
[Show abstract][Hide abstract] ABSTRACT: Darwin devised sexual selection theory to explain sexual dimorphisms. Further developments of the theory identified the operational sex-ratio (OSR) as one of its cornerstones, and it was commonly admitted that an OSR biased toward one sex would lead to stronger selection pressures toward that sex. Recent theoretical developments have challenged this view and showed that the OSR alone does not determine the direction of sexual selection, more particularly in mutually ornamented species exhibiting high and similar parental investment by both sexes. These developments, however, focused on mutual intersexual selection, and little is known about intrasexual selection of both males and females in species exhibiting such characteristics. The first aim of our study was to test the relative involvement of males and females in same-sex contest over mates in the king penguin, a species exhibiting mutual ornamentation of the sexes, high parental investment by both sexes, and a male-biased OSR. We investigated the sex composition of trio parades, which are groups of three individuals that compete for mates during pair formation. We found that these trios consist of a female trailed by two fighting males in 19 of 20 cases; the 20th trio was all male. The second aim of our study was to investigate the existence of within-sex differences in colour ornaments between individuals involved in such trios and individuals already paired. While limited sample sizes precluded detection of statistically significant differences between trios vs. pairs, reflectance measurements suggested that the beak spot of males in trios were more strongly ultraviolet than the beak spot of males in pairs. We concluded that intrasexual selection in our colony follows the typical pattern of mate competition observed in species in which sexual dimorphisms and OSR are male biased, and discussed the ultraviolet difference within the framework of the king penguins' colour perception.
[Show abstract][Hide abstract] ABSTRACT: King penguins (Aptenodytes patagonicus) live in large and densely populated colonies, where navigation can be challenging due to the presence of many conspecifics that could obstruct locally available cues. Our previous experiments demonstrated that visual cues were important but not essential for king penguin chicks' homing. The main objective of this study was to investigate the importance of non-visual cues, such as magnetic and acoustic cues, for chicks' orientation and short-range navigation. In a series of experiments, the chicks were individually displaced from the colony to an experimental arena where they were released under different conditions. In the magnetic experiments, a strong magnet was attached to the chicks' heads. Trials were conducted in daylight and at night to test the relative importance of visual and magnetic cues. Our results showed that when the geomagnetic field around chicks was modified, their orientation in the arena and the overall ability to home was not affected. In the low sound experiment we limited the acoustic cues available to the chicks by putting ear pads over their ears, and in the loud sound experiment we provided additional acoustic cues by broadcasting colony sounds on the opposite side of the arena to the real colony. In the low sound experiment, the behavior of the chicks was not affected by the limited sound input. In the loud sound experiment, the chicks reacted strongly to the colony sound. These results suggest that king penguin chicks may use the sound of the colony while orienting towards their home.
Journal of Experimental Biology 01/2013; · 3.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Olfactory cues have been shown to be important to homing petrels at night, but apparently those procellariiform species that also come back to the colony during the day are not impaired by smell deprivation. However, the nycthemeral distribution of homing, i.e. whether displaced birds released at night return to their burrow by night or during daylight, has never been investigated. To explore this question, we studied the homing behaviour of Cory's shearwater (Calonectris borealis) in the only known population where these birds are active at the colony both during the day and the night. Here, we compared the nocturnal versus diurnal homing schedule of birds treated with zinc sulphate to induce a reversible but complete anosmia, to that of controls. Our results show that anosmic shearwaters were unable to home in the dark and were constrained to wait for the daylight to find their burrow again. Our results confirm that olfaction is the basic sensory input for homing by night even in a petrel species that is diurnally active at the colony.
Journal of Experimental Biology 01/2013; · 3.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The survival of marine predators depends on behavioural plasticity to cope with changes in prey distribution. Variability in behaviour might predict plasticity and is easier to assess than plasticity. Using miniaturized GPS loggers over several breeding seasons in two Norwegian Northern gannet (Morus bassanus) colonies, we investigated if and how the variability within and between individuals, but also between colonies and years, affected foraging strategies. Results revealed strong individual variability (foraging trip durations, foraging effort and different foraging areas). Individuals from both colonies showed preferred commuting routes, flight bearings and feeding hotspots. Individuals from the largest colony used larger and more foraging areas than individuals from the small colony. Feeding hotspots and foraging ranges varied amongst years in the largest colony only. Our study demonstrated that gannets show flexibility by changing prey fields that are driven by shifting oceanographic conditions.
[Show abstract][Hide abstract] ABSTRACT: Mate choice for major histocompatibility complex (MHC) compatibility has been found in several taxa, although rarely in birds. MHC is a crucial component in adaptive immunity and by choosing an MHC-dissimilar partner, heterozygosity and potentially broad pathogen resistance is maximized in the offspring. The MHC genotype influences odour cues and preferences in mammals and fish and hence olfactory-based mate choice can occur. We tested whether blue petrels, Halobaena caerulea, choose partners based on MHC compatibility. This bird is long-lived, monogamous and can discriminate between individual odours using olfaction, which makes it exceptionally well suited for this analysis. We screened MHC class I and II B alleles in blue petrels using 454-pyrosequencing and quantified the phylogenetic, functional and allele-sharing similarity between individuals. Partners were functionally more dissimilar at the MHC class II B loci than expected from random mating (p = 0.033), whereas there was no such difference at the MHC class I loci. Phylogenetic and non-sequence-based MHC allele-sharing measures detected no MHC dissimilarity between partners for either MHC class I or II B. Our study provides evidence of mate choice for MHC compatibility in a bird with a high dependency on odour cues, suggesting that MHC odour-mediated mate choice occurs in birds.
Proceedings of the Royal Society B: Biological Sciences 09/2012; 279(1746):4457-4463. · 5.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ALBATROSSES DO SOMETHING THAT NO OTHER BIRDS ARE ABLE TO DO: fly thousands of kilometres at no mechanical cost. This is possible because they use dynamic soaring, a flight mode that enables them to gain the energy required for flying from wind. Until now, the physical mechanisms of the energy gain in terms of the energy transfer from the wind to the bird were mostly unknown. Here we show that the energy gain is achieved by a dynamic flight manoeuvre consisting of a continually repeated up-down curve with optimal adjustment to the wind. We determined the energy obtained from the wind by analysing the measured trajectories of free flying birds using a new GPS-signal tracking method yielding a high precision. Our results reveal an evolutionary adaptation to an extreme environment, and may support recent biologically inspired research on robotic aircraft that might utilize albatrosses' flight technique for engineless propulsion.
PLoS ONE 09/2012; 7(9):e41449. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Highlights
► European storm petrel seabirds are able to avoid relatives in pair formation. ► We show that European storm petrels discriminate by olfaction kin from nonkin. ► European storm petrels may avoid inbreeding by using chemical information. ► Sophisticated olfactory communication is relevant in birds.
[Show abstract][Hide abstract] ABSTRACT: Once one of the most numerous seabirds of the Benguela upwelling system, the population of Cape cormorants Phalacrocorax capensis has decreased by 60% in the last three decades and the species is listed as Near-threatened. Declines in prey availability and/or abundance brought about by recent changes in the distribution of pelagic fish stocks and industrial purse-seine fishing are hypothesized to be a key driver of seabird population decreases in the southern Benguela. We investigated the foraging behaviour of breeding Cape cormorants by deploying GPS and temperature-depth recorders (TDRs) on 24 breeding adults from three islands off the coast of South Africa, two of them to the north of Cape Point and a third further south on the western Agulhas Bank. This provided the first measures of foraging dispersal by a cormorant in the Benguela system, and enabled a comparison of foraging behaviour between birds from these islands. Foraging trips of Cape cormorants lasted between 17min and >7h, at a maximum distance of between 2 and 58 km away from their colony. Foraging effort was significantly greater for birds from further north off the west coast in terms of trip duration, distance travelled, number of dives and time spent flying compared to those from the southernmost island (Dyer), which is probably a response to low prey availability in the north. Coastal reserves that exclude pelagic fishing from inshore feeding grounds around Cape cormorant breeding colonies may result in increased local prey availability, which would benefit Cape cormorant populations.
[Show abstract][Hide abstract] ABSTRACT: Knowledge on how divers exploit the water column vertically in relation to water depth is crucial to our understanding of their ecology and to their subsequent conservation. However, information is still lacking for the smaller-bodied species, due mostly to size constraints of data-loggers. Here, we report the diving behaviour of a flying diving seabird, the Cape Cormorant Phalacrocorax capensis, weighing 1.0–1.4 kg. Results were obtained by simultaneously deploying small, high resolution and high sampling frequency GPS and time-depth loggers on birds breeding on islands off Western South Africa (34°S, 18°E) in 2008. In all, dive category was assigned to all dives per-formed by 29 birds. Pelagic dives occurred almost as fre-quently as benthic dives. Pelagic dives were shallow (mean: 5 m) and took place over seafloors 5–100 m deep. Benthic dives were deeper, occurring on seafloors mainly 10–30 m deep. Dive shape was linked to dive category in only 60% of dives, while the descent rate, ascent rate and bottom dura-tion/dive duration ratio of a dive best explained its dive category. This shows that only the concomitant use of tracking and depth tags can adequately classify diving strategies in a diver like the Cape Cormorant. Diet was mainly Cape Anchovy Engraulis encrasicolis, suggesting that birds probably displayed two contrasted strategies for capturing the same prey. Flexible foraging techniques rep-resent an important key to survival inside the highly pro-ductive but heterogeneous Benguela upwelling ecosystem.
[Show abstract][Hide abstract] ABSTRACT: Haematology can provide useful information to assess the health of free-ranging animals. In seabirds, many procellariiform (albatrosses and petrels) species undertake long-distance migrations during which individuals may get in contact with birds and pathogens of different biogeographic origin. Although checking whether procellariiformes might play a role in large-scale spread of diseases is desirable, haematological data have been published in very few species. For the first time, we determined blood cell counts in Cory's shearwater, Calonectris diomedea, a petrel which breeds in the western Palearctic but overwinters off Brazil and South Africa. Forty-five adult Cory's shearwaters were captured in their burrows in the Azores archipelago during the pre-laying period in March 2008, measured, weighed, and a blood sample was taken from each of them. Haematocrit, polychromasia, leukocyte and thrombocyte counts did not differ significantly between sexes, but total leukocyte number was significantly (positively) correlated with body condition.
Italian Journal of Zoology 09/2011; 78(3):279-286. · 0.87 Impact Factor