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Recently-adopted foraging strategies constrain early chick development in a coastal breeding gull.

ABSTRACT: Human-mediated food sources offer possibilities for novel foraging strategies by opportunistic species. Yet, relative costs and benefits of alternative foraging strategies vary with the abundance, accessibility, predictability and nutritional value of anthropogenic food sources. The extent to which such strategies may ultimately alter fitness, can have important consequences for long-term population dynamics. Here, we studied the relationships between parental diet and early development in free-ranging, cross-fostered chicks and in captive-held, hand-raised chicks of Lesser Black-backed Gulls (Larus fuscus) breeding along the Belgian coast. This traditionally marine and intertidal foraging species is now increasingly taking advantage of human activities by foraging on terrestrial food sources in agricultural and urban environments. In accordance with such behavior, the proportion of terrestrial food in the diet of free-ranging chicks ranged between 4% and 80%, and consistent stable isotope signatures between age classes indicated that this variation was mainly due to between-parent variation in feeding strategies. A stronger terrestrial food signature in free-ranging chicks corresponded with slower chick development. However, no consistent differences in chick development were found when contrasting terrestrial and marine diets were provided ad libitum to hand-raised chicks. Results of this study hence suggest that terrestrial diets may lower reproductive success due to limitations in food quantity, rather than quality. Recent foraging niche expansion toward terrestrial resources may thus constitute a suboptimal alternative strategy to marine foraging for breeding Lesser Black-backed Gulls during the chick-rearing period.

SUBMITTER: Sotillo A

PROVIDER: S-EPMC6626513 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Recently-adopted foraging strategies constrain early chick development in a coastal breeding gull.

Sotillo Alejandro A Baert Jan M JM Müller Wendt W Stienen Eric W M EWM Soares Amadeu M V M AMVM Lens Luc L

PeerJ 20190710

Human-mediated food sources offer possibilities for novel foraging strategies by opportunistic species. Yet, relative costs and benefits of alternative foraging strategies vary with the abundance, accessibility, predictability and nutritional value of anthropogenic food sources. The extent to which such strategies may ultimately alter fitness, can have important consequences for long-term population dynamics. Here, we studied the relationships between parental diet and early development in free- ...[more]

PMID: 31333907

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Project description:BackgroundIn species with biparental care both members of the breeding pair cooperate to raise the offspring either by assisting each other in every reproductive task or by specializing in different ones. The latter case is known as reproductive role specialization. Raptors are considered one of the most role-specialized groups, but little is known about parental behavior away from the nest. Until the advent of biologgers, avian role specialization was traditionally studied with direct observations at the nest because of the difficulties of following and recording the behavior of free-ranging individuals. In this paper we analyze how the role specialization of the lesser kestrel (Falco naumanni) influences foraging movement patterns throughout the breeding season. We tracked 30 lesser kestrel breeders from two breeding colonies using high-frequency GPS-dataloggers during four consecutive breeding seasons.ResultsWe found no differences between sexes in lesser kestrel foraging movements early in the breeding season before the formation of the breeding pair. However, we observed sexually distinct foraging movement strategies later in the breeding season once breeding pairs were formed. Lesser kestrel males performed a large number of short foraging trips while females made a few long ones. This maximized the provisioning rate by males to feed their mates and offspring. Meanwhile, lesser kestrel females spent more time at the colony than males in order to defend the nest, incubate the eggs and brood the nestlings. Females also helped their mates to provision the nestling once these had grown and required more food and less protection. Furthermore, lesser kestrels showed a sexual spatial segregation in foraging areas, with males foraging closer to the colony than females.ConclusionsThe lesser kestrel responds to changes in energy demand throughout the breeding season with its foraging movement strategy, but in a different way depending on parental sex. The sexual spatial segregation observed is likely to be the result of an adaptive foraging strategy based on role specialization to reduce prey depletion close to the colony and intersexual competition in order to improve breeding success.

Project description:Herring gulls (Larus argentatus) are opportunistic feeders, resulting in contaminant exposure depending on area and habitat. We compared contaminant concentrations and dietary markers between two herring gull breeding colonies with different distances to extensive human activity and presumed contaminant exposure from the local marine diet. Furthermore, we investigated the integrity of DNA in white blood cells and sensitivity to oxidative stress. We analyzed blood from 15 herring gulls from each colony-the urban Oslofjord near the Norwegian capital Oslo in the temperate region and the remote Hornøya island in northern Norway, on the Barents Sea coast. Based on d13 C and d34 S, the dietary sources of urban gulls differed, with some individuals having a marine and others a more terrestrial dietary signal. All remote gulls had a marine dietary signal and higher relative trophic level than the urban marine feeding gulls. Concentrations (mean ± standard deviation [SD]) of most persistent organic pollutants, such as polychlorinated biphenyl ethers (PCBs) and perfluorooctane sulfonic acid (PFOS), were higher in urban marine (PCB153 17 ± 17 ng/g wet weight, PFOS 25 ± 21 ng/g wet wt) than urban terrestrial feeders (PCB153 3.7 ± 2.4 ng/g wet wt, PFOS 6.7 ± 10 ng/g wet wt). Despite feeding at a higher trophic level (d15 N), the remote gulls (PCB153 17 ± 1221 ng/g wet wt, PFOS 19 ± 1421 ng/g wet wt) were similar to the urban marine feeders. Cyclic volatile methyl siloxanes were detected in only a few gulls, except for decamethylcyclopentasiloxane in the urban colony, which was found in 12 of 13 gulls. Only hexachlorobenzene was present in higher concentrations in the remote (2.6 ± 0.42 ng/g wet wt) compared with the urban colony (0.34 ± 0.33 ng/g wet wt). Baseline and induced DNA damage (doublestreak breaks) was higher in urban than in remote gulls for both terrestrial and marine feeders. Environ Toxicol Chem 2022;41:2466-2478. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

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Project description:The feeding strategies of Ocypode gaudichaudii at two sandy beaches, Culebra Beach (CB) and Playa Venao (PV) in Panama, were studied via three experiments. Two separate manipulative in situ experiments were conducted to determine how the densities of food resources and the size of the supplemented food offered to the crabs can affect their diet and food handling behavior. The third experiment, a transplantation study, was also conducted to determine the plasticity of the feeding behavior of the displaced crabs. In the first experiment, freshly-emerged crabs showed different feeding modes when washed-sediment was seeded with different densities of diatoms and rove beetles, which suggests that they are optimal foragers. Crabs hoarded food in the second experiment when food augmentation was performed, in which small and large food pellets were placed around the burrows at the beginning and end of the crabs' feeding cycle. All freshly-emerged crabs from both sites foraged on the small pellets outside their burrows and did not cache food; when pellets were provided at the end of the feeding cycle, crabs from CB fed on some of the small pellets and returned to their burrows with the uneaten pellets left on the surface, whereas crabs at PV picked up all the small food pellets and transferred them into their burrows over several trips before plugging their burrow entrances. Only the crabs from PV carried the large food pellets supplemented at the start and end of the feeding cycle into their burrows. In contrast, the crabs at CB often left behind the partially-eaten pellets on the sand surface, probably due to the increased risk of predation associated with the prolonged handling time of the large food pellets. Excavation of the burrows of the crabs that hoarded food showed that all the pellets were deposited at the bend of the burrows, indicating that they were not consumed immediately. Crabs that fed in droves at PV stopped droving and foraged around their burrows after being transplanted to CB. This is the first documentation of food hoarding in a sandy beach macroinvertebrate at a resource-impoverished habitat. The plasticity of feeding strategies adopted by the painted ghost crab in response to different densities of food resources in the habitat could be an adaptation to the dynamic sandy beach environment.

Dataset Information

Recently-adopted foraging strategies constrain early chick development in a coastal breeding gull.

Publications

Recently-adopted foraging strategies constrain early chick development in a coastal breeding gull.

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