Flexible foraging patterns under different time constraints in tropical boobies

doi:10.1016/j.anbehav.2004.04.007

Animal Behaviour

Volume 68, Issue 6, December 2004, Pages 1331-1337

https://doi.org/10.1016/j.anbehav.2004.04.007 Get rights and content

The foraging behaviour of any animal is intricately linked to ecological constraints. Extrinsic factors, such as daylength, may limit the time available for foraging. Intrinsic factors, such as the coordination of mates at a nest site, may exacerbate this limitation. Using activity loggers, we examined the effects of extrinsic and intrinsic limitations on the foraging behaviour of the sympatric red-footed booby, Sula sula, and brown booby, Sula leucogaster, during incubation, and tested the prediction that individuals would work harder when time available for foraging was limiting. Both species share incubation duties and forage by day. Brown boobies made significantly shorter foraging trips than red-footed boobies, and thus, both parents could forage during the same day. Therefore, departure time and time available for foraging will also be influenced by when the partner returns to the colony. Overall foraging trip duration decreased linearly with respect to departure time. Our study suggests that the time available for foraging is limited by a combination of extrinsic and intrinsic processes in both species. Crucially, the rate of flying and diving, indicators of prey search and pursuit, respectively, increased with decreasing time available for foraging, whereas time spent inactive on the sea surface decreased, as did the time between departure and diving. Our data therefore suggest that boobies adjust their foraging behaviour according to extrinsic constraints.

Section snippets

Methods

We carried out the study from 4 to 23 March 2003 at a colony of ca. 450 breeding pairs of brown boobies and ca. 1400 breeding pairs of red-footed boobies on Johnston Atoll (16°N, 169°W) in the central Pacific Ocean. The study site was close to the equator with approximately 12 h of daylight each day. Sunrise and sunset occurred at ca. 0730 and 1930 hours Pacific Time, respectively. The U.S. Fish and Wildlife Service granted access to the Atoll and permission to attach loggers to boobies.

Using a

Results

In both species, activity showed a strong diurnal pattern with foraging occurring during the day and birds incubating at the nest or roosting in the colony at night (Fig. 2). No individual left the colony before ca. 0500 hours and only one of the 56 birds, a red-footed booby, spent the night sitting on the water, returning to the colony the next evening after 2 full days at sea foraging. The mean trip duration of brown boobies was significantly shorter than that of red-footed boobies (Table 1),

Discussion

Boobies had a flexible daily foraging strategy that was linked to the time available to forage. In both species of booby, foraging behaviour during incubation was strongly influenced by daylight. Both measures of dive rate and the proportion of time spent in flight increased as the number of hours of daylight available decreased. The flight duration before the first dive of a trip and the return flight home after the last dive were significantly shorter in trips that departed later in the day.

Acknowledgments

We thank Gerrit Peters for extensive support with the data loggers (PreciTD, earth & OCEAN Technologies, D-24113 Kiel, Germany) and Gary McCloskey and his staff on Johnston Atoll for help with logistics. Thanks to Morten Frederiksen for useful discussion, to David Elston for statistical support and to two anonymous referees for very useful comments. This work was funded by a Small Ecological Project Grant from the British Ecological Society to S.L. and by the U.S. Army Chemical Demil Program to

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Daylight in Europa during the studied seasons was on average 12.5 h and trips lasted on average 6.4 ± 4.4 h, allowing each partner of a pair to make a foraging trip during the same day. If the limited-time of daylight represents a constraint to foraging, it is less apparent in Europa than for example in Johnston Atoll (central Pacific Ocean), where average trip duration of RFB was 14 h (Lewis et al., 2004), i.e. slightly longer than the local daylight duration. Foraging trips at Europa were longer than at Tromelin Island where mean duration was 4 h and maximum range was 31 km (Kappes et al., 2011).
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Despite many biotic, physical, and political challenges for place-based conservation in open ocean environments, conservation of discrete oceanic regions by designating pelagic marine protected areas (PMPAs) has gained considerable traction. In the oligotrophic central Pacific, a patchy and dynamic ecosystem, a robust network of PMPAs has recently been established. However, evaluations of PMPA efficacy in providing appropriate habitat coverage for pelagic species are lacking, particularly in the tropics. Here, we used high resolution GPS tracking and home range analyses of tropical boobies to determine the distribution and foraging habitat use of three sympatric species (Sula sula, Sula dactylatra, and Sula leucogaster) in two PMPAs that varied substantially in size and shape. At each site we characterized the extent and use of foraging habitat inside and outside the PMPA that surrounded each breeding colony. We found profound variation within and among species in foraging behavior and habitat use across the two sites; this was partially explained by variation in bathymetry. Yet, despite variation both in PMPA size and shape, and in foraging behavior of the birds, we determined that the PMPAs each encapsulated more than 85% (n = 216 trips) of foraging habitat for each species, indicating that these PMPAs provided important habitat coverage for highly mobile tropical species. While this study highlights the challenges in effectively designing PMPAs even for relatively well-studied, central place foragers, given strong variation in foraging ecologies across sites, it also suggests that PMPAs do provide meaningful habitat coverage for at least some pelagic species.
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A growing body of evidence suggests that behavioral variability can come under control of discriminative stimuli. The present experiment further examined discriminative control of variability in a novel way by using the discrimination-reversal paradigm. Eight pigeons responded under a multiple schedule of Vary and Yoke components signaled by different-colored keylights. In the Vary component, 4-response sequences that differed from the previous 10 produced food, while in the Yoke component, any 4-response sequence had a fixed probability of producing food, yoked to the prior Vary component. Following stability in this procedure, the key colors signaling the Vary and Yoke components were reversed across four successive conditions. Across the experiment, variability of keypeck sequences was higher in the Vary than in the Yoke component. Across successive reversals, the level of variability in the Vary component adapted more rapidly to the reversed contingencies, while the rate of adaptation in the Yoke component did not change systematically. These results are interpreted in terms of the different contingencies in the Vary and Yoke components. In addition, the improvement in the rate of adaptation across successive reversals in the Vary component appears consistent with a proactive interference account of discrimination-reversal performance. These results join others in suggesting that variability may be an operant dimension of behavior.
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¹: E. A. Schreiber and G. A. Schenk are at the Bird Department, National Museum of Natural History, MRC 116, Washington, D.C. 20560, U.S.A.

²: K. C. Hamer is at the School of Biology, University of Leeds, Leeds LS2 9JT, U.K.

View full text

Flexible foraging patterns under different time constraints in tropical boobies

Section snippets

Methods

Results

Discussion

Acknowledgments

Journal of Thermal Biology

Advanced Studies in Behaviour

Animal Behaviour

Sea bird ecology and the marine environment

Flight energetics of free-ranging red-footed boobies (Sula sula)

Physiological Zoology

Activity-specific metabolic rates of free-living northern gannets and other seabirds

Ecology

Variation in daily and seasonal foraging routines of non-breeding barnacle geese (Branta leucopsis): working harder does not overcome environmental constraints

Journal of Zoology

Rapid-response recorders reveal interplay between marine physics and seabird behaviour

Marine Ecology Progress Series

The prudent parent: energetic adjustments in avian breeding

Ardea

Introduction to REML for Scientists

Sexual dimorphism and sexual segregation in foraging strategies of northern giant petrels, Macronectes halli, during incubation

Oikos

The Oystercatcher: From Individuals to Populations

The effect of time and digestion constraints in common eiders while feeding and diving over blue mussel beds

Functional Ecology

Foraging ranges, diets and feeding locations of gannets Morus bassanus in the North Sea: evidence from satellite telemetry

Marine Ecology Progress Series

Contrasting foraging strategies of gannets Morus bassanus at two North Atlantic colonies: foraging trip duration and foraging area fidelity

Marine Ecology Progress Series

Day length, latitude and behavioural (in)flexibility in baboons (Papio cynocephalus ursinus)

Behavioral Ecology and Sociobiology