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Time of day is recognized as an important behaviour modulator of wild animals mainly via physical environmental changes such as temperature and light intensity. These temporal factors can also affect animal movements (i.e., changes of locations) and consequent distribution. However, while it is commonly observed in diverse taxa that an animal’s attendance at a specific site concentrates within a narrow time window, how time influences the route selections of traveling animals in the course of their movements through to the end point is still not well understood. In this study, we quantified temporal and spatial patterns in the homing paths of streaked shearwaters Calonectris leucomelas, which are present at the breeding colony exclusively after sunset, to investigate how time constrains their movement strategy for homing from at-sea foraging areas. We tracked the foraging trips using GPS loggers in chick-rearing seasons for five years. In addition, in one year we conducted displacement experiments, releasing birds at sea at three different times of the day (midday, sunset and night-time) to impose time constraints on homeward movements. The movement paths revealed that the time of sunset was key to their decision of timing and in route selections during homing. Most birds returning from foraging trips reached the coastal area around sunset by adjusting travel timing and directions, despite variation in foraging areas, and flew along the coastline to the breeding island. Meanwhile, most birds released offshore stopped flights around sunset and waited on the water surface for sunrise before restarting their homeward movements. Birds therefore avoid offshore traveling at night, appearing to preferentially use diurnal cues for homing at sea. This study demonstrates the importance of timing as well as geographic features for homing decisions of streaked shearwaters and confirms that both spatial and temporal cognitive abilities are well developed in seabirds.

Anthropogenic marine debris is a threat to marine organisms. Understanding how this debris spatially distributes at sea and may become associated with marine wildlife are key steps to tackle this current issue. Using bird-borne GPS- and video-loggers on 13 black-footed albatrosses Phoebastria nigripes breeding in Torishima, Japan, we examined the distribution of large floating debris in the Kuroshio Current area, western North Pacific. A total of 16 floating debris, including styrofoam (n = 4), plastic pieces (n = 3), plastic sheet (n = 1), fishery-related items (rope or netting, n = 4), and unidentified debris (n = 4), were recorded across the 9003 km covered by nine birds. The debris was concentrated in the southern area of the Kuroshio Current, where the surface current was weak, and the albatrosses were foraging. The albatrosses displayed changes in flight direction towards the debris when at a mean distance of 4.9 km, similarly to when approaching prey, and one bird was observed pecking at a plastic sheet; indicating that albatrosses actively interacted with the debris. This paper shows the usefulness of studying wide-ranging marine predators through the use of combined biologging tools, and highlights areas with increased risk of debris exposure and behavioral responses to debris items.

BackgroundEcholocating bats make a series of decisions to select their flight paths based on auditory information obtained by sonar as well as visual cues; accumulations of these flight routes are represented as daily movement patterns. However, there is still a lack of an understanding of continuous movements of echolocating bats in the wild (i.e., from meters to tens of kilometers). In this study, we investigated nightly flight paths of the Japanese greater horseshoe bat, Rhinolophus ferrumequinum nippon, using high-resolution GPS data loggers. Our aim was to identify foraging and commuting behavior based on the observed movement patterns and to investigate the relationship between these movement types and specific habitats. ResultsWe found that the majority of tagged bats alternated between foraging and commuting behavior throughout the tracking period, and one individual moved 23.6 km from its roost. The bats usually left a foraging area in the opposite direction from which they entered it, indicating that almost all of the stay sites were on their way to another destination. The distance between two successive foraging sites was on average 332 ± 398 m (mean ± standard deviation), and half of all foraging periods lasted less than 3 min. An analysis of habitat use revealed that the bats used conifer plantation and natural forests as pathways and feeding habitats. ConclusionsOur findings suggest that the structure of the forests have a great influence on the nocturnal behavior of the greater horseshoe bats. Although this study has a descriptive character due to a relatively small number of tagged individuals, it was possible to elucidate the small-scale interactions between wild Rhinolophus bats and their environment using the latest high-resolution GPS technology, which will allow us to give new insights into the foraging ecology of echolocating bats in the wild.

This review summarizes the advances in bio-logging technology that enables us to monitor foraging behavior, movement, behavioral performance, physiological performance, and sociality in a wide rang...

Between 25–30 November 2013, 2014 and 2015, miniaturized video cameras were attached to Magellanic Penguins (Spheniscus magellanicus; n = 14) in Punta Norte/San Lorenzo, Peninsula Valdes, Chubut, Argentina. The objective was to examine prey selection, consumption of untraceable prey, and inter- and intraspecific interactions. During 56.3 hr of video footage, 1,621 dives from 14 individuals were recorded. Magellanic Penguins swam through shoals of lobster krill (Munida gregaria morph subrugosa), selectively consuming the fish, primarily anchovies (Engraulis anchoita), that were dispersed along the shoal, but did not consume the lobster krill. Magellanic Penguins captured fish on dives of less than 2 m in depth. The tagged individuals foraged with conspecifics in 2% (n = 33) of the total recorded dives. In addition, a multispecies feeding association was also documented (n = 1). Results were constrained to the upper 40 m of the water column; below this depth light level was too low for detections by video. The development of cameras with a light source and wider-angle lens are crucial to improve our understanding of Magellanic Penguin foraging behavior.

To understand foraging strategies and behavioral flexibility in wild animals, it is important to evaluate the physiological costs imposed by foraging efforts and how these costs affect foraging and provisioning behavior. Oxidative stress is a possible physiological indicator associated with foraging behavior in wild seabirds, and may also affect their reproductive performance. However, no previous study has simultaneously recorded foraging behavior and the associated oxidative stress in wild seabirds. Using an integrative approach based on oxidative stress measurements and bio-logging techniques (i.e., the use of animal-borne sensors), we determined the relationships between foraging behavior and oxidative stress in chick-rearing streaked shearwaters Calonectris leucomelas in 2018 and 2019. To quantify their oxidative stress, we measured reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) in their plasma. We found that the d-ROMs levels were positively related to the maximum distance from the colony and the number of takeoffs, especially in 2019 when shearwaters flew further to forage. In 2018, when they flew relatively short distances, the BAP levels were positively related to the levels of their physical activity (overall dynamic body acceleration; ODBA). We conclude that longer and less successful foraging may lead to increase oxidative stress, while successful foraging may mitigate the oxidative stress of foraging by providing dietary antioxidants. Our results highlight that the combined data from bio-logging and oxidative stress measurements aid in evaluating the underlying physiological costs of foraging behavior in wild animals.

Sex-related differences in foraging habitat are common among seabirds. Streaked Shearwaters Calonectris leucomelas breeding on Awashima Island in the Sea of Japan are considered to exhibit gender differences in foraging habitat: only males cross the windy Tsugaru Strait into the Pacific Ocean. Since males are larger, with greater wing loading than females, winds are expected to increase the effect of sexual size dimorphism on their flight performance, which may determine accessibility to foraging habitats. To assess the sex-related differences in foraging movements among years in which environmental and wind conditions differed, we analyzed foraging trips of male (N=243) and female (N=241) Streaked Shearwaters during the chick-rearing period by using GPS loggers in 2011, 2012, and 2013. Both males and females were found to travel through the Tsugaru Strait into the Pacific Ocean, but the frequency was higher for males than for females. Nevertheless, we found that wind velocities had no effect on ...

There is increasing evidence showing that wind velocity affects the flight and foraging behavior of seabirds; however, few studies have examined these effects on seabirds inhabiting tropical oceans where lighter wind conditions usually prevail. The Brown Booby Sula leucogaster is an example of a tropical seabird with relatively low wing loading; strong wind conditions may be expected to impede the stability of their flight. We examined how different wind conditions affected the duration and flying behavior of Brown Booby fledglings during foraging trips by means of direct observation of nest attendance and by attaching video loggers to birds. The duration of foraging trips by fledglings decreased with increasing wind speed, and during flight, the body rotation of fledglings became greater with increasing wind speed. As expected, fledglings were buffeted by strong winds due to their relative inexperience in flight combined with their low wing loading. Fledglings were probably forced to flap agains...

Large-scale flight paths of echolocating Japanese greater horseshoe bats were measured using GPS and acoustic GPS (A-GPS) data-loggers. The bats flew up to 23.6 km away from their roost at a maximum. The measured flight paths were broadly divided into two patterns; “staying” and “moving”. Almost bats spent over 70% of time staying while changing sites, indicating that the bats repeated to stay and to fly, and spent much time staying. Analysis for the environmental preference revealed that the bats selectively move and stay in the forest and tend to move along the artificial road. These findings by the high-resolution GPS bio-logging suggest that the bats repeat to stop the various area for foraging, by following the artificial forest roads. Furthermore, the collected A-GPS logger showed that more pulse emissions were observed during staying than moving, strongly supporting that the bats search prey insects using sonar while perching on the tree at the stay-site. Further investigation by A-GPS bio-logging would provide valuable information on bat's echolocation and flight strategies during natural foraging in the large-scale space.

How do wild animals behave as they get older? We investigated the foraging behavior of black-tailed gulls (Larus crassirostris) of known age using GPS and acceleration loggers. We found that the older gulls reduced their mean flight speed and tended to feed on prey on land rather than on prey at sea. However, breeding performance of gulls did not change with age. Therefore, older gulls might experience senescence, but optimize their foraging behavior in relation to their age to maintain breeding performance.

Streaked shearwaters (Calonectris leucomelas) are pelagic seabirds that breed on isolated islands in East Asia. Sometimes, they fly long distances to search and forage for food over several hundred kilometers. During the chick-rearing period, efficient foraging is one of the most important tasks for parents because they have to obtain food not only for themselves but also for their chicks. To understand their foraging strategy of streaked shearwaters, their behavior and physiological cost should be quantified. In 2018, we attached GPS and acceleration loggers on breeding shearwaters (15 males and 11 females, including eight pairs) and collected blood samples from them at the deployment and recovery of the loggers. We confirmed that blood drawing from Streaked shearwaters did not have significant adverse effect on their foraging behaviors. We found oxidative and anti-oxidative markers via blood can be useful for assessing the physiological cost of their foraging behaviors. Our finding suggests that females were suffered from heavier stress than males, because females often conducted short trips and increased oxidative stress. To reveal how they perform foraging with minimal cost, we are going to analyze the relationship between foraging behavior and the associated physiological cost in detail.

Revealing the route selection of wild animals is of fundamental importance in understanding their movements and foraging strategy. In this study, we attached GPS loggers to black-tailed gulls Larus crassirostris and recorded their movement trajectories during their foraging trips. Using inverse reinforcement learning (IRL), we analyzed the factors that affected their route selection. During the training phase, using pre-defined feature maps, we estimated a reward map that may affect the decision making of black-tailed gulls. The reward map can be used for predicting the trajectories of the gulls during the test phase. In addition, the resultant weight vector enabled us to analyze to which degree the black-tailed gulls favor each area.

Offspring transmit signals to parents to communicate their resource demands. Parents interpret these signals and should adjust provisioning efforts to meet offspring demands but only to the point at which the benefits of enhanced offspring quality stops exceeding the increased costs to future reproduction. We investigated both proximate behavioral mechanisms in these interactions and ultimate-level decisions for total parental investment in streaked shearwaters Calonectris leucomelas by recording begging calls, monitoring parental attendance, and altering states of chicks by supplementing food. In our study, chicks seemed to honestly communicate satiety and body condition via begging. The parents, however, did not downwardly adjust feeding rates, meal sizes delivered to chicks, and total investment in nests in which chicks were regularly supplementary-fed partial meals. But on nights when both parents visited the nest, the second-arriving parents recognized that chicks had already received a full meal because they reduced the food they gave to chicks and also lengthened their subsequent foraging trip. Our findings therefore suggest that although chick begging appeared to reflect need, parents only responded to variation in begging that indicated that chicks had already received a full meal. In a simulation, we show that this strategy prevents parents from exceeding the optimal amount of parental investment. Their insensitivity to slightly reduced begging after partial meals caused them to exceed optimal investment in supplementary-fed nests, suggesting that parental investment is largely regulated by responses to feeding rate of the other parent rather than being fine-tuned to cues about body condition of chicks.

Ocean currents are in continuous motion and strongly influence oceanic ecosystems. In situ observation of currents is of primary importance for understanding how marine animals respond to ocean surface currents at various scales and for realizing effective ecosystem-based management and realistic oceanographic modelling. We developed a new method for obtaining in situ current measurements by using seabirds as Lagrangian current sensors akin to drifting buoys. We deployed high-resolution global positioning system (GPS) loggers on streaked shearwaters (Calonectris leucomelas) foraging in the Oyashio-Tsugaru Warm Current confluence in Japan, which is one of the most productive oceans in the world. The seabirds repeatedly performed foraging trips, including searching for prey and resting on the sea surface, over several hundred kilometres. The seabirds spent half of their time resting on the water surface and tended to be passive drifters. We inferred that the drift movements of C. leucomelas provided a direct and detailed description of the ocean surface currents, because currents deduced from their drift movements were in good agreement with ocean surface currents derived from in situ and satellite data. In addition, we extracted details of shearwaters’ intense searching flights associated with feeding (i.e. foraging spots) from GPS tracks. C. leucomelas did not forage at the core of anticyclonic eddies; rather, they used the boundary areas between eddies and the edge of eddies where primary productivity and prey density are thought to be high. Our study demonstrated that animal-borne GPS data can provide a detailed and cost-efficient tool for observing ocean surface currents and can reveal the ways in which marine animals respond to these currents at a fine scale.

Timing is crucial for animals for optimizing foraging, travelling and breeding behaviours in spatiotemporally heterogeneous environments. Some seabirds, commuting between land-based nesting colonies and widely dispersed foraging areas at sea, return to their colonies within several hours after sunset. This temporal pattern raises the question of how they manage to time arrivals over largely variable homeward distances. However, no study has investigated their at-sea behavioural patterns associated with arrival times. To explore this question, we tracked breeding streaked shearwaters, Calonectris leucomelas, with GPS data loggers, which continuously recorded fine-scale movement paths during their trips. Shearwaters adjusted the onset of their homeward journeys according to wide-ranging distances between their chosen foraging areas and breeding colonies, leaving earlier from further locations. The start time of homing was pushed forward correlating with the increased travel time expected from their homeward distance and average movement speed. This resulted in arrivals at the colony concentrated within a few hours after sunset independent of the distances. To our knowledge, similar temporal tuning of homing trips has not been reported previously. The strong correlation between the timing and distance of homeward journeys implies this behaviour is ecologically important. Further experiments will help clarify its generality in the animal kingdom as well as proximate mechanism(s) and ultimate function(s).

The lunar cycle has been shown to affect the behaviour of a variety of marine animals. However, changes in the behaviour of seabirds and marine mammals and how they respond to the lunar cycle have been less well documented, principally because of the technical difficulties in long-term recording of their at-sea behaviour. Because seabirds generally rely on visual cues at small spatial scales, ambient light levels by moonlight may have a strong influence on their foraging and predator avoidance behaviours at sea at night. We used global location sensor loggers attached to wintering streaked shearwaters to examine whether the birds' at-sea behaviour varied with the lunar phase. The shearwaters migrated from Japan to the seas off northern New Guinea. Their activities at night changed synchronously with the lunar phase: birds flew for longer periods and landed on water more frequently on nights with a full moon than when there was a new moon. Our results indicate that at-sea behaviour of pelagic seabirds is closely associated with the lunar cycle.

Brown Boobies (Sula leucogaster) obtain prey by plunge dives. In order to investigate the foraging behaviour of Brown Boobies underwater, we attached acceleration data loggers to chick-rearing Brown Boobies at Nakanokamishima Island in Japan. We documented, for the first time, Brown Boobies performing many rapid and shallow V-shaped dives and some W-shaped dives during the daylight period. The average and maximum dive depth and duration were 1.03 m and 3.81 m and 1.83 s and 21 s, respectively. Furthermore, Brown Boobies used buoyancy to ascend to the water surface. Our data suggest that Brown Boobies mainly depend on shallow-plunging, contrary to the pursuit divers such as gannets, due to their ecological and/or physiological constraints.

Externally-attached transmission and logging devices have greatly helped elucidate the biology of free-living animals over the last 50 yr. However, such devices may hinder animals so that the behaviour monitored is not representative of unequipped conspecifics. We suggest that if animals are equipped with devices of varying size, the change in recorded parameters with size can be used to extrapolate to the condition in unencumbered animals. Use of this approach with Adelie penguins Pygoscelis adeliae showed that unequipped birds are predicted to range farther, swim faster, dive deeper and be more efficient underwater than equipped birds. The derived data not only set baseline information for the species concerned but also allow us to put the deleterious effects of the devices into perspective.

Changes in sea-ice conditions can affect locomotion on land, diving behavior, and corresponding foraging success of penguins. In this study, locomotion on land and diving behavior were compared between early and late stages of the guard phase with different sea-ice conditions using miniaturized time-depth-acceleration data loggers for Adelie penguins Pygoscelis adeliae from 18 December 2001 to 11 January 2002 in Dumont d’Urville, Adelie Land (66.7°S, 140.0°E), Antarctica. Differences were found between early and late stages in the ratio of walking vs. tobogganing, proportion of time spent diving, diving depth as well as in the rate of parental tissue accumulation. In contrast, trip duration, distance traveled on land, and meal delivery rate to chicks did not differ between the stages. This study suggests that physical changes in sea-ice during the penguins’ chick-rearing period may affect certain on-land and/or at-sea behaviors which, in turn, may affect how resources are allocated to self-maintenance or chick-provisioning.

During the last few years, the development of animal-borne still cameras and video recorders has enabled researchers to observe what a wild animal sees in the field. In the present study, we deployed miniaturized video recorders to investigate the underwater foraging behavior of Imperial cormorants (Phalacrocorax atriceps). Video footage was obtained from 12 animals and 49 dives comprising a total of 8.1 h of foraging data. Video information revealed that Imperial cormorants are almost exclusively benthic feeders. While foraging along the seafloor, animals did not necessarily keep their body horizontal but inclined it downwards. The head of the instrumented animal was always visible in the videos and in the majority of the dives it was moved constantly forward and backward by extending and contracting the neck while travelling on the seafloor. Animals detected prey at very short distances, performed quick capture attempts and spent the majority of their time on the seafloor searching for prey. Cormorants foraged at three different sea bottom habitats and the way in which they searched for food differed between habitats. Dives were frequently performed under low luminosity levels suggesting that cormorants would locate prey with other sensory systems in addition to sight. Our video data support the idea that Imperial cormorants' efficient hunting involves the use of specialized foraging techniques to compensate for their poor underwater vision. Fil: Gómez Laich, Agustina Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina Fil: Yoda, Ken. Nagoya University; Japón Fil: Zavalaga, Carlos. Universidad Científica del Sur; Perú. Nagoya University; Japón Fil: Quintana, Flavio Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Wildlife Conservation Society; Estados Unidos

A new method using acceleration data loggers enabled us to measure the porpoising behaviour of Adélie penguins (Pygoscelis adeliae), defined as a continuous rapid swimming with rhythmic serial leaps. Previous hydrodynamic models suggested that leaping would be energetically cheaper when an animal swims continuously at depths of less than three maximum body diameters below the water surface. In the present study, free-ranging Adélie penguins leapt at a mean speed of 2.8 m s−1 above the predicted threshold speed (0.18–1.88 m s−1). Wild penguins reduced drag by swimming deeper (0.91 m) and did not swim continuously within the high-drag layer while submerged. This indicates that previous calculations may be incomplete. Moreover, leaps represented an average of only 3.8 % of the total distance travelled during the porpoising cycle, which would make energy savings marginal. Among the six penguins used in our study, two did not porpoise and three porpoised for less than 7 min, also indicating that this behaviour was not important during travel to and from foraging sites, as has been previously suggested. Birds mainly porpoised at the start and end of a trip. One explanation of porpoising might be an escape behaviour from predators.

Ocean-scale monitoring of pollution is challenging. Seabirds are useful indicators because they travel over a broad foraging range. Nevertheless, this coarse spatial resolution is not fine enough to discriminate pollution in a finer scale. Previous studies have demonstrated that pollution levels are higher in the Sea of Japan and South and East China Seas than the Northen Pacific Ocean. To test these findings in a wide-ranging animal, we tracked streaked shearwaters (Calonectris leucomelas) from four islands in Japan using global positioning system (GPS) and measured persistent organic pollutants (POPs) in the oil of their preen glands. The POPs did not change during 6 to 21 days when birds from Awashima were foraging only in the Sea of Japan, while it increased when they crossed to the Pacific through the Tsugaru Strait and foraged along the eastern coast of Hokkaido where industrial cities occur. These results indicate that POPs in the oil reflect relatively short-term exposure. Concentrations of POPs displayed greater variation among regions. Total polychlorinated biphenyls were highest in birds foraging in a small area of the semiclosed Seto Inland Sea surrounded by urbanized coast, p,p'-dichlorodiphenyltrichloroethane (DDT) was highest in birds foraging in the East China Sea, and total hexachlorocyclohexanes were highest in birds foraging in the Sea of Japan. All were lowest in birds foraging in the Pacific. This distribution of POPs concentration partly agrees with previous findings based on mussels, fish, and seawater and possibly reflects the mobility and emission sources of each type of POP. These results highlight the importance of information on the foraging area of highly mobile top predators to make them more effective monitors of regional marine pollution.

The biosonar (click train) production rate of ten Yangtze finless porpoises and their behavior were examined using animal-borne data loggers. The sound production rate varied from 0 to 290 click trains per 10-min time interval. Large individual differences were observed, regardless of body size. Taken together, however, sound production did not differ significantly between daytime and nighttime. Over the 172.5 h of analyzed recordings, an average of 99.0% of the click trains were produced within intervals of less than 60 s, indicating that during a 1-min interval, the number of click trains produced by each porpoise was typically greater than one. Most of the porpoises exhibited differences in average swimming speed and depth between day and night. Swimming speed reductions and usage of short-range sonar, which relates to prey-capture attempts, were observed more often during nighttime. However, biosonar appears to be affected not only by porpoise foraging, but also by their sensory environment, i.e., the turbid Yangtze River system. These features will be useful for passive acoustic detection of the porpoises. Calculations of porpoise density or abundance should be conducted carefully because large individual differences in the sound production rate will lead to large estimation error.

The mesopelagic zone of the northeast Pacific Ocean is an important foraging habitat for many predators, yet few studies have addressed the factors driving basin-scale predator distributions or inter-annual variability in foraging and breeding success. Understanding these processes is critical to reveal how conditions at sea cascade to population-level effects. To begin addressing these challenging questions, we collected diving, tracking, foraging success, and natality data for 297 adult female northern elephant seal migrations from 2004 to 2010. During the longer post-molting migration, individual energy gain rates were significant predictors of pregnancy. At sea, seals focused their foraging effort along a narrow band corresponding to the boundary between the sub-arctic and sub-tropical gyres. In contrast to shallow-diving predators, elephant seals target the gyre-gyre boundary throughout the year rather than follow the southward winter migration of surface features, such as the Transition Zone Chlorophyll Front. We also assessed the impact of added transit costs by studying seals at a colony near the southern extent of the species’ range, 1,150 km to the south. A much larger proportion of seals foraged locally, implying plasticity in foraging strategies and possibly prey type. While these findings are derived from a single species, the results may provide insight to the foraging patterns of many other meso-pelagic predators in the northeast Pacific Ocean.

In seabirds, the relationship between flight speed and wind direction/speed is thought to be particularly important for studying energy-saving strategy and foraging habitat selection. In this study, we examined whether the ground and calculated air speeds of four great cormorants (Phalacrocorax carbo) were affected by wind conditions using high-resolution GPS data loggers. The birds increased their ground flight speed in tailwinds, decreased it in headwinds, and changed their air speed in relation to wind components. However, they did not change their foraging sites according to the wind conditions. They were likely to respond to moderate wind conditions by adjusting their air speed without changing their foraging sites.

Most seabirds are diurnal foragers, but some species may also feed at night. In Peruvian pelicans (Pelecanus thagus), the evidence for nocturnal foraging is sparse and anecdotal. We used GPS-dataloggers on five incubating Peruvian pelicans from Isla Lobos de Tierra, Peru, to examine their nocturnality, foraging movements and activities patterns at sea. All instrumented pelicans undertook nocturnal trips during a 5-7 day tracking period. Eighty-seven percent of these trips (n = 13) were strictly nocturnal, whereas the remaining occurred during the day and night. Most birds departed from the island after sunset and returned a few hours after sunrise. Birds traveled south of the island for single-day trips at a maximum range of 82.8 km. Overall, 22% of the tracking period was spent at sea, whereas the remaining time was spent on the island. In the intermediate section of the trip (between inbound and outbound commutes), birds spent 77% of the trip time in floating bouts interspersed by short flying bouts, the former being on average three times longer than the latter. Taken together, the high sinuosity of the bird's tracks during floating bouts, the exclusively nocturnal trips of most individuals, and the fact that all birds returned to the island within a few hours after sunrise suggest that pelicans were actively feeding at night. The nocturnal foraging strategy of Peruvian pelicans may reduce food competition with the sympatric and strictly diurnal Guanay cormorants (Phalacrocorax bougainvillii), Peruvian boobies (Sula variegata) and Blue-footed boobies (S. nebouxii), which were present on the island in large numbers. Likewise, plankton bioluminescence might be used by pelicans as indirect cues to locate anchovies during their upward migration at night. The foraging success of pelicans at night may be enhanced by seizing prey close to the sea surface using a sit-and-wait strategy.

While social interactions play a crucial role on the development of young individuals, those of highly mobile juvenile birds in inaccessible environments are difficult to observe. In this study, we deployed miniaturised video recorders on juvenile brown boobies Sula leucogaster, which had been hand-fed beginning a few days after hatching, to examine how social interactions between tagged juveniles and other birds affected their flight and foraging behaviour. Juveniles flew longer with congeners, especially with adult birds, than solitarily. In addition, approximately 40% of foraging occurred close to aggregations of congeners and other species. Young seabirds voluntarily followed other birds, which may directly enhance their foraging success and improve foraging and flying skills during their developmental stage, or both.

How do birds acquire flight skills after fledging? This issue is important, as it is closely related to variation in the duration of offspring care, the causes of which remain unknown. In this study, we raised hatchling brown boobies, Sula leucogaster, and attached an acceleration data logger to each bird at fledging to record its movements. This allowed us to quantify precisely the time spent flapping, gliding and resting. The duration of foraging trips and proportion of time spent gliding during flight increased with the number of days since fledging, whereas the proportion of time spent in flight decreased. This indicates that brown boobies gradually acquire efficient flight skills during the post-fledging period, which might be the proximate cause of the long postfledging care period in this species. To the authors' knowledge, this is the first study to record precisely the ontogeny of flight behaviour in birds.

Measurement of the time allocation of penguins at sea has been a major goal of researchers in recent years. Until now, however, no equipment has been available that would allow measurement of the aquatic and terrestrial behaviour of an Antarctic penguin while it is commuting between the colony and the foraging grounds. A new motion detector, based on the measurement of acceleration, has been used here in addition to current methods of inferring behaviour using data loggers that monitor depth and speed. We present data on the time allocation of Adelie penguins (Pygoscelis adeliae) according to the different types of behaviours they display during their foraging trips: walking, tobogganing, standing on land, lying on land, resting at the water surface, porpoising and diving. To illustrate the potential of this new technique, we compared the behaviour of Adelie penguins during the chick-rearing period in a fast sea-ice region and an ice-free region. The proportion of time spent standing, lying on land and walking during foraging trips was greater for penguins in the sea-ice region (37.6+/−13.3% standing, 21.6+/−15.6% lying and 5.9+/−6.3% walking) than for those in the ice-free region (12.0+/−15.8 % standing, 0.38+/−0.60% lying and 0 % walking), whereas the proportion of time spent resting at the water surface and porpoising was greater for birds in the ice-free region (38.1+/−6.4% resting and 1.1+/−1.1% porpoising) than for those in the sea-ice region (3.0+/−2.3% resting and 0% porpoising; means +/− s.d., N=7 for the sea-ice region, N=4 for the ice-free region). Using this new approach, further studies combining the monitoring of marine resources in different Antarctic sites and the measurement of the energy expenditure of foraging penguins, e.g. using heart rates, will constitute a powerful tool for investigating the effects of environmental conditions on their foraging strategy. This technique will expand our ability to monitor many animals in the field.