Larus Marinus Research Articles

CGull: A Non-Flapping Bioinspired Composite Morphing Drone.

Despite the tremendous advances in aircraft design that led to successful powered flights of aircraft as heavy as the Antonov An-225 Mriya, which weighs 640 tons, or as fast as the NASA-X-43A, which reached a record of Mach 9.6, many characteristics of bird flight have yet to be utilized in aircraft designs. These characteristics enable various species of birds to fly efficiently in gusty environments and rapidly change their momentum in flight without having modern thrust vector control (TVC) systems. Vultures and seagulls, as examples of expert gliding birds, can fly for hours, covering more than 100 miles, without a single flap of their wings. Inspired by the Great Black-Backed Gull (GBBG), this paper presents "CGull", a non-flapping unmanned aerial vehicle (UAV) with wing and tail morphing capabilities. A coupled two degree-of-freedom (DOF) morphing mechanism is used in CGull's wings to sweep the middle wing forward and the outer feathered wing backward, replicating the GBBG's wing deformation. A modular two DOF mechanism enables CGull to pitch and tilt its tail. A computational model was first developed in MachUpX to study the effects of wing and tail morphing on the generated forces and moments. Following the biological construction of birds' feathers and bones, CGull's structure is mainly constructed from carbon-fiber composite shells. The successful flight test of the proof-of-concept physical model proved the effectiveness of the proposed morphing mechanisms in controlling the UAV's path.

Mercury contamination and potential health risk to French seabirds: A multi-species and multi-site study

Mercury (Hg) is a naturally occurring highly toxic element which circulation in ecosystems has been intensified by human activities. Hg is widely distributed, and marine environments act as its main final sink. Seabirds are relevant bioindicators of marine pollution and chicks are particularly suitable for biomonitoring pollutants as they reflect contamination at short spatiotemporal scales. This study aims to quantify blood Hg contamination and identify its drivers (trophic ecology inferred from stable isotopes of carbon (δ13C) and nitrogen (δ15N), geographical location, chick age and species) in chicks of eight seabird species from 32 French sites representing four marine subregions: the English Channel and the North Sea, the Celtic Sea, the Bay of Biscay and the Western Mediterranean. Hg concentrations in blood ranged from 0.04 μg g−1 dry weight (dw) in herring gulls to 6.15 μg g−1 dw in great black-backed gulls. Trophic position (δ15N values) was the main driver of interspecific differences, with species at higher trophic positions showing higher Hg concentrations. Feeding habitat (δ13C values) also contributed to variation in Hg contamination, with higher concentrations in generalist species relying on pelagic habitats. Conversely, colony location was a weak contributor, suggesting a relatively uniform Hg contamination along the French coastline. Most seabirds exhibited low Hg concentrations, with 74% of individuals categorized as no risk, and < 0.5% at moderate risk, according to toxicity thresholds. However, recent work has shown physiological and fitness impairments in seabirds bearing Hg burdens considered to be safe, calling for precautional use of toxicity thresholds, and for studies that evaluate the impact of Hg on chick development.

Path analysis reveals combined winter climate and pollution effects on the survival of a marine top predator.

Marine ecosystems are experiencing growing pressure from multiple threats caused by human activities, with far-reaching consequences for marine food webs. Determining the effects of multiple stressors is complex, in part, as they can affect different aspects of biological organisation (behaviour, individual traits and demographic rates). Determining the combined effects of stressors, through different biological pathways, is key to predict the consequences for the viability of populations threatened by global change. Due to their position in the food chain, top predators such as seabirds are considered more sensitive to environmental changes. Climate change is affecting the prey resources available for seabirds, through bottom-up effects, while organic pollutants can bioaccumulate in food chains with the greatest impacts on top predators. However, knowledge of their combined effects on population dynamics is scarce. Using a path analysis, we quantify the effects of climate change and pollution on the survival of adult great black-backed gulls, both directly and through effects of individuals' body mass. Warmer ocean temperatures in gulls' winter foraging areas in the North Sea were correlated with higher survival, potentially explained by shifts in prey availability associated with global climate change. We also found support for indirect negative effects of organochlorines, highly toxic pollutants to seabirds, on survival, which acted, in part, through a negative effect on body mass. The results from this path analysis highlight how, even for such long-lived species where variance in survival tends to be limited, two stressors still have had a marked influence on adult survival and illustrate the potential of path models to improve predictions of population variability under multiple stressors.

Plastic ingestion, accumulated heavy metals, and health metrics of four Larus gull species feeding at a coastal landfill in eastern Canada

The objectives of this research were to assess ingested plastics and accumulated heavy metals in four urban gull species. Additionally, the relationships between ingested plastics and selected demographic and health metrics were assessed. Between 2020–2021 during the non-breeding seasons, 105 gulls (46 American herring gulls (HERG, Larus argentatus smithsonianus), 39 great black-backed gulls (GBBG, Larus marinus), 16 Iceland gulls (Larus glaucoides), 4 glaucous gulls (Larus hyperboreus)) were killed at a landfill in coastal Newfoundland and Labrador, Canada, as part of separate, permitted kill-to-scare operations related to aircraft safety. Birds were necropsied, the upper gastrointestinal tract contents were processed using standard techniques, and livers were analyzed for accumulated As, Cd, Hg, and Pb. The relationships between ingested plastics, demographics, and health metrics were assessed in HERG and GBBG. Across all four species, 85 % of birds had ingested at least one piece of anthropogenic debris, with 79 % ingesting at least one piece of plastic. We detected interspecific differences in plastic ingestion and hepatic trace metals, with increased ingested plastics detected in GBBG compared with HERG. For GBBG, levels of ingested plastic were relatively greater for birds with higher scaled mass index, while HERG with more ingested plastic had higher liver lead concentrations.

Physiological effects of PFAS exposure in seabird chicks: A multi-species study of thyroid hormone triiodothyronine, body condition and telomere length in South Western France

There is growing evidence that poly and perfluoroalkyl substances (PFAS) exposure leads to the disruption of thyroid hormones including thyroxine (T4) and triiodothyronine (T3), and may affect telomeres, repetitive nucleotide sequences which protect chromosome ends. Many seabird species are long-lived top predators thus exhibit high contaminant levels, and PFAS-disrupting effects on their physiology have been documented especially in relation to the endocrine system in adults. On the contrary, studies on the developmental period (i.e., chicks), during which exposure to environmental contaminants may have a greater impact on physiological traits, remain scarce to this date. We carried out a multi-species study with the aim to assess whether and to which extent chicks of four gull species (herring gull, great and lesser black-backed gull, yellow-legged gull) in South Western France are contaminated by PFAS, and to bring further evidence about their potential physiological consequences. Linear PFOS showed concentrations of concern as it was generally >10 times higher than the other PFAS, and exceeded a threshold toxicity level (calculated from previous studies in birds) in almost all sampled chicks. Nonetheless, in herring gull male chicks, total T3 levels were significantly and negatively associated with perfluorodecanoate (PFDA) and perfluorododecanoate (PFDoDA) and positively associated with perfluorotetradecanoate (PFTeDA) in female chicks. Total T3 levels were also positively associated with PFDoDA in great black backed gull male chicks and with perfluorotridecanoate (PFTrDA) in lesser black backed gull chicks. In lesser and great black-backed gulls, both females and males showed significant negative associations between several PFAS and their body condition, and a positive association between telomere length and L-PFOS in the yellow-legged gull was also found. These results corroborate previous findings and need to be further explored as they suggest that PFAS may interfere with the physiological status of chicks during the developmental period, potentially inducing long-lasting consequences.

Reduced breeding success in Great Black‐backed Gulls (Larus marinus) due to harness‐mountedGPSdevice

Animal‐borne bio‐logging devices are routinely fitted to seabirds to learn about their behaviour and physiology, as well as their interactions with the marine environment. The assessment and reporting of deleterious impacts from such devices on the individuals carrying them is critical to inform future work and improve data quality and animal welfare. We assessed the impacts of thoracic‐harness attachments on the breeding performance and inter‐annual return rates of Great Black‐backed Gulls. We found that tagged individuals hatched fewer eggs per nest (0.67) than two different control groups (handled but not tagged – 2.0, and not handled – 1.9) and had lower hatching success rates per nest (27% compared with 81% and 82% in control groups). Inter‐annual return rates were similar between tagged and control groups, but the harness attachment potentially caused the death of an individual 5 days after deployment. Overall, the harness attachment was a lead driver of nest failure. We urge extreme caution for those wanting to use harness‐mounted devices on Great Black‐backed Gulls.

Quantifying the impacts of predation by Great Black-backed Gulls Larus marinus on an Atlantic Puffin Fratercula arctica population: Implications for conservation management and impact assessments

The management of predator-prey conflicts can be a key aspect of species conservation. For management approaches to be effective, a robust understanding of the predator-prey relationship is needed, particularly when both predator and prey are species of conservation concern. On the Isle of May, Firth of Forth, Scotland, numbers of breeding Great Black-backed Gulls Larus marinus, a generalist predator, have been increasing since the 1980s, which has led to increasing numbers of sympatrically breeding Atlantic Puffins Fratercula arctica being predated during the breeding season. This may have consequences for species management on the Isle of May and impact assessments of offshore windfarms in the wider Firth of Forth area. We used population viability analysis to quantify under what predation pressure the Atlantic Puffin population may decline and become locally extinct over a three-generation period. The predation level empirically estimated in 2017 (1120 Puffins per year) was not sufficient to drive a decline in the Puffin population. Rather, an increase to approximately 3000 Puffins per year would be required to cause a population decline, and >4000 to drive the population to quasi-extinction within 66 years. We discuss the likelihood of such a scenario being reached on the Isle of May, and we recommend that where predator-prey conflicts occur, predation-driven mortality should be regularly quantified to inform conservation management and population viability analyses associated with impact assessments.

Effects of sodium heparin on δ13C, δ15N and δ34S values in avian whole blood

Anticoagulants are often added to avian blood samples immediately after collection to allow plasma to be extracted at a later time, but the effects of anticoagulants on stable isotope studies are not well understood. We use a Bayesian approach to assess the effects of sodium heparin, one of the most commonly used anticoagulants, on δ13C, δ15N and δ34S values in avian whole blood using Herring Gulls Larus argentatus and Great Black‐backed Gulls Larus marinus as study species. We found that the addition of sodium heparin only had a significant effect on δ34S values (−0.4‰) and that this effect did not meaningfully impact the estimated diet proportions of broad‐scale stable isotope mixing models, and only slightly affected the output of finer‐scale stable isotope mixing models. Our results highlight that researchers should be aware of the possible impacts of sodium heparin on measured stable isotope values in avian blood, particularly for δ34S, and that this effect should be carefully considered relative to the scale and particulars of the study (e.g. generalist versus specialist species and broad‐scale versus fine‐scale analyses).

Predator exclusion fencing improves productivity at a mixed colony of Herring Gulls Larus argentatus, Lesser Black-backed Gulls L. fuscus and Great Black-backed Gulls L. marinus

Predator exclusion fencing improves productivity at a mixed colony of Herring Gulls Larus argentatus, Lesser Black-backed Gulls L. fuscus and Great Black-backed Gulls L. marinus

Predator exclusion fencing improves productivity at a mixed colony of Herring Gulls Larus argentatus, Lesser Black-backed Gulls L. fuscus and Great Black-backed Gulls L. marinus

A large multi-species gull colony at South Walney in Cumbria, northwest England, has suffered declines over the past 20 years, and from 2016 to 2020 no gull chicks fledged despite up to 4,000 pairs of adults attempting to breed each year. The primary cause of nest failure was predation. In an attempt to reverse this decline, a predator exclusion fence was erected around the remnant gull colony in March 2021, and population and productivity surveys were carried out over the 2021 and 2022 breeding seasons. In 2021, 53, 27 and 40 chicks fledged from 263 Herring Gull, 186 Lesser Black-backed and 38 Great Black-backed Gull nests, respectively, resulting in reproductive success rates of 0.20, 0.15, and 1.05 fledglings per nest. Following the fence erection, in 2022 numbers of nesting birds increased by 151% overall to 575 Herring Gull nests, 553 Lesser Black-backed Gull nests and 28 Great Black-backed Gull nests, with reproductive success rates of 0.4, 0.61 and 1.21 respectively.

Nevtollur og nýggjari føroysk lóggáva um oyðing av skaðafugli

The socalled beak duty was an obligation for all grownsup men in the Faroe Islands to deliver one beak of a raven (corvus corax varius) a year. The duty is mentionned as early as in Olaus Magnus (1555), who, to be sure, traces it to Iceland, and presumably it is of mediaeval origin. It was imposed for the purpose of reducing the damage caused to the stock of sheep by the ravens, which especially killed the young lambs. The payment of the beak duty had to be enjoined several times in the course of the 17th century and the beginning of the 18th century, whereupon detailed rules were laid down by Royal Ordinance of November 21, 1741. Pursuant to this ordinance it was possible in addition to beaks of ravens to deliver beaks of eagles (haliaeetus albicilla), of crows (corvus cornix cornix), and of blackbacks (larus marinus). The provision of the ordinance regarding the eagle was of little importance, this bird being already at that time extirpated as a breeding bird, and complete agreement does not seem to have prevailed as to the noxiousness of the crow and the blackback to the stock of sheep. Besides these birds, the great skua (stercorarius skua skua) is known to have been under the beak duty, which, to all appearance, contributed towardsits almost complete extirpation so that a preservation of it had to be effected in 1897, with the result that the stock of this bird has increased again. Svabo suggested about 1780 that the lesser black^backed gull (larus fuscus graellsii) ought to come under the beak duty, too, but his proposal was not carried through. Besides, opinions differed on the noxiousness of this bird. The beak duty was abolished by an Act in 1881, the opinion being that the system gave too much trouble and that it was not necessary any longer. The latter supposition was not right, however, and an awarding of prizes had to be introduced immediately, and it was also necessary by and Act of March 11, 1892 to put landowners under the obligation to seek out the nests of the raven and to destroy the brood. However, this act was never applied to any great extent, whereas the awardingof prizes has been maintained up to our time. At present small prizes are awarded for deliveries of beaks both of the raven and of the crow.

Colonization and Extirpation of Great Black-Backed Gulls (Larus marinus) Nesting on Lake Ontario and the Upper St. Lawrence River

Colonies of Herring (Larus argentatus) and/or Ring-billed Gulls (L. delawarensis) on Lake Ontario and the upper St. Lawrence River were searched annually, 1981–2018, for nesting Great Black-backed Gulls (L. marinus). Great Black-backed Gulls nested at nine sites where both Herring and Ring-billed Gulls nested, at seven sites with only Herring Gulls, and at one site where they nested solitarily. Nests per site ranged from 1–21 on Lake Ontario and 1–5 on the St. Lawrence River. On Lake Ontario, nest numbers increased from six nests in 1981 to 51 nests in 2001 (+ 11.3%/yr), then declined to zero nests in 2008, where they have remained ever since. The decline in nesting Great Black-backed Gulls was due primarily to mortality from Type E botulism that affected that species to a greater degree than other gull species, probably because of their superior ability to dominate and scavenge toxin-laden carrion. Temporal changes in routes and efficiency of botulinum toxin transfer likely explain why Great Black-back Gulls were initially able to colonize Lake Ontario, but have undergone extirpation in recent times. Our results illustrate how changes in disease prevalence in the Great Lakes can degrade environmental quality to the extent that some species simply cannot persist.

Bird eggs

I once spent a summer studying gulls on Appledore Island in the Gulf of Maine, off the east coast of the United States. The rocky island is a breeding colony for herring gulls (Larus argentatus) and great black-backed gulls (Larus marinus), so I had a front-row seat to the dramas that unfolded as birds paired up, laid and incubated eggs, and raised chicks. I saw chicks hatch from large speckled eggs (Figure 1A), a Herculean feat that took over an hour. Eggs and chicks are extremely vulnerable, and many gull offspring do not survive. Now, when a gull soars past - or pilfers my sandwich at the beach - I appreciate the hurdles it overcame just to reach adulthood.

A threat from both sides: Multiple introductions of genetically distinct H5 HPAI viruses into Canada via both East Asia-Australasia/Pacific and Atlantic flyways.

From 2016 to 2020, high pathogenicity avian influenza (HPAI) H5 viruses circulated in Asia, Europe, and Africa, causing waves of infections and the deaths of millions of wild and domestic birds and presenting a zoonotic risk. In late 2021, H5N1 HPAI viruses were isolated from poultry in Canada and also retrospectively from a great black-backed gull (Larus marinus), raising concerns that the spread of these viruses to North America was mediated by migratory wild bird populations. In February and April 2022, H5N1 HPAI viruses were isolated from a bald eagle (Haliaeetus leucocephalus) and broiler chickens in British Columbia, Canada. Phylogenetic analysis showed that the virus from bald eagle was genetically related to H5N1 HPAI virus isolated in Hokkaido, Japan, in January 2022. The virus identified from broiler chickens was a reassortant H5N1 HPAI virus with unique constellation genome segments containing PB2 and NP from North American lineage LPAI viruses, and the remaining gene segments were genetically related to the original Newfoundland-like H5N1 HPAI viruses detected in November and December 2021 in Canada. This is the first report of H5 HPAI viruses' introduction to North America from the Pacific and the North Atlantic-linked flyways and highlights the expanding risk of genetically distinct virus introductions from different geographical locations and the potential for local reassortment with both the American lineage LPAI viruses in wild birds and with both Asian-like and European-like H5 HPAI viruses. We also report the presence of some amino acid substitutions across each segment that might contribute to the replicative efficiency of these viruses in mammalian host, evade adaptive immunity, and pose a potential zoonotic risk.

Recent changes in colony sizes of two seabird species in Scotland are not strongly influenced by Birds Directive status of the colony

Special Protection Areas (SPAs) designated under the EU Birds Directive have improved the conservation status of many terrestrial bird species in Europe, but protecting breeding sites may be less effective for highly mobile birds such as seabirds. Colony census data for Great Skuas Stercorarius skua and Great Black‐backed Gulls Larus marinus in Scotland show that breeding numbers have fared no better in sites where these species are SPA breeding features and, counter‐intuitively, the evidence indicates better performance in non‐SPA colonies, most likely because non‐SPA colonies are generally smaller so are less subject to density‐dependent competition. The main drivers of population change are widespread rather than colony‐based in these two species with recent reductions in carrying capacity. Many other seabird species are vulnerable to similar widespread pressures so seabird conservation strategy needs to focus on mitigating these pressures, as designation of seabird breeding sites as SPAs is not enough to ensure effective seabird conservation.

Blood mercury concentrations in four sympatric gull species from South Western France: Insights from stable isotopes and biologging

Mercury (Hg) is a toxic trace element widely distributed in the environment, which particularly accumulates in top predators, including seabirds. Among seabirds, large gulls (Larus sp) are generalist feeders, foraging in both terrestrial and marine habitats, making them relevant bioindicators of local coastal Hg contamination. In the present study, we reported blood Hg concentrations in adults and chicks of four different gull species breeding on the French Atlantic coast: the European herring gull (Larus argentatus), the Lesser black-backed gull (L. fuscus), the Great black-backed gull (L. marinus) and the Yellow-legged gull (L. michahellis). We also investigated the potential role of foraging ecology in shaping Hg contamination across species, using the unique combination of three dietary tracers (carbon, nitrogen and sulfur stable isotopes) and biologging (GPS tracking). A high concentration of Hg was associated with high trophic position and a marine diet in gulls, which was corroborated by birds’ space use strategy during foraging trips. Adults of all four species reached Hg concentrations above reported toxicity thresholds. Specifically, adults of Great black-backed gulls had a high trophic marine specialized diet and significantly higher Hg concentrations than the three other species. Blood Hg was 4–7 times higher in adults than in chicks, although chicks of all species received mainly marine and high trophic position prey, which is expected to be the cause of blood Hg concentrations of toxic concern. By using both stable isotopes and GPS tracking, the present study provides compelling insights on the main feeding habits driving Hg contamination in a seabird assemblage feeding in complex coastal environments.

Preliminary study of gull (Laridae) scavenging and dispersal of vertebrate remains, Shoals Marine Laboratory, Coastal New England

The taphonomic effects of avian taxa upon forensic scenes has been little researched, and shore species including gulls (Laridae) have received even less attention, despite their well-known behavior as scavengers of human food waste. In order to begin assessing their potential impact, a pilot study was undertaken on Appledore Island, Maine, USA, at the Shoals Marine Laboratory. This location was chosen for its isolation from most other vertebrate scavengers and its large, seasonal breeding colonies of gulls, primarily great black-backed (Larus marinus) and herring (L. argentatus) gulls. Two locations with fresh bones were monitored for scavenging activity, using trail cameras and Tile Mate® tracking chips. In addition, portions of the breeding colonies nesting areas along the rocky coast were surveyed for bones that must have derived at some distance from human-generated trash sources. All (n=16) fresh bones underwent dispersal by gulls, with an average distance of 10m and a maximum distance (in one case) of 85 m. Multiple bones from trash sources were transported a minimum of 150 m if locally acquired and a minimum of 10km if acquired from the mainland. These bones had a maximum length of 192 mm and mass of 46.0g. Gulls, with their global distribution, have the potential to be significant dispersers of human skeletal remains and should undergo additional taphonomic research.

Age and season predict influenza A virus dynamics in urban gulls: consequences for natural hosts in unnatural landscapes.

Gulls are ubiquitous in urban areas due to a growing reliance on anthropogenic feeding sites, which has led to changes in their abundance, distribution, and migration ecology, with implications for disease transmission. Gulls offer a valuable model for testing hypotheses regarding the dynamics of influenza A virus (IAV) - for which gulls are a natural reservoir in urban areas. We sampled sympatric populations of Ring-billed (Larus delawarensis), Herring (L. argentatus), and Great Black-backed Gulls (L. marinus) along the densely populated Atlantic rim of North America to understand how IAV transmission is influenced by drivers such as annual cycle, host species, age, habitat type, and their interplay. We found that horizontal transmission, rather than vertical transmission, played an outsized role in the amplification of IAV due to the convergence of gulls from different breeding grounds and age classes. We detected overlapping effects of age and season in our prevalence model, identifying juveniles during autumn as the primary drivers of the seasonal epidemic in gulls. Gulls accumulated immunity over their lifespan, however short-term fluctuations in seroprevalence were observed, suggesting that migration may impose limits on the immune system to maintain circulating antibodies. We found that gulls in coastal urban habitats had higher viral prevalence than gulls captured inland, correlating with higher richness of waterbird species along the coast, a mechanism supported by our movement data. The peak in viral prevalence in newly fledged gulls that are capable of long-distance movement has important implications for the spread of pathogens to novel hosts during the migratory season as well as for human health as gulls increasingly utilize urban habitats.

Closely related gull species show contrasting foraging strategies in an urban environment

The expansion of urban landscapes has both negative and positive effects on wildlife. Understanding how different species respond to urbanization is key to assessing how urban landscapes influence regional wildlife behavior and ecosystem structure. Gulls are often described as strong urban adapters, but few studies have explored species-specific differences in habitat use. Here, we use GPS tracking in conjunction with stable isotope analysis (SIA) to quantify the habitat use and trophic ecology of great black-backed gulls (Larus marinus) and herring gulls (L. argentatus) in an urbanized area. Non-Metric Multidimensional Scaling (NMDS) of foraging locations revealed significant differences in the habitat use between species. Great black-backed gulls foraged primarily in marine habitats and herring gulls foraged primarily in specific urban habitats (e.g., landfills, dumpsters) and showed higher site fidelity in terms of the proportion of foraging sites revisited. Further, great black-backed gulls had significantly higher δ15N and δ13C than herring gulls, reflecting the use of marine, rather than urban, food sources. This study highlights the variability in urban habitat utilization among closely related species, assesses stable isotope signatures of urban diets in wild birds, and discusses ecological implications of the relative contribution of urban and marine foraging.

Different individual-level responses of great black-backed gulls (Larus marinus) to shifting local prey availability.

To grow, survive and reproduce under anthropogenic-induced changes, individuals must respond quickly and favourably to the surrounding environment. A species that feeds on a wide variety of prey types (i.e. generalist diet) may be comprised of generalist individuals, specialist individuals that feed on different prey types, or a combination of the two. If individuals within a population respond differently to an environmental change, population-level responses may not be detectable. By tracking foraging movements of great black-backed gulls (Larus marinus), a generalist species, we compared group-level and individual-level responses to an increase in prey biomass (capelin; Mallotus villosus) during the breeding season in coastal Newfoundland, Canada. As hypothesized, shifts in prey availability resulted in significantly different individual responses in foraging behaviour and space use, which was not detectable when data from individuals were combined. Some individuals maintained similar foraging areas, foraging trip characteristics (e.g., trip length, duration) and habitat use with increased capelin availability, while others shifted foraging areas and habitats resulting in either increased or decreased trip characteristics. We show that individual specialization can be non-contextual in some gulls, whereby these individuals continuously use the same feeding strategy despite significant change in prey availability conditions. Findings also indicate high response diversity among individuals to shifting prey conditions that a population- or group-level study would not have detected, emphasizing the importance of examining individual-level strategies for future diet and foraging studies on generalist species.