High individual flexibility in the foraging behavior of a marine predator, the common murre

Gulka, Julia; Davoren, Gail K.

doi:10.1007/s00227-019-3530-4

Cited by 20 publications

(16 citation statements)

References 89 publications

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“…spawning) Capelin availability. This delineation was corroborated by Capelin biomass estimates from weekly hydroacoustic surveys (Gulka & Davoren 2019).…”

Section: Methodssupporting

confidence: 55%

“…Murres had the narrowest niche breadth and were most enriched in δ 15 N and δ 13 C (plasma only) among the alcids during higher Capelin availability. This suggests an initial mid‐trophic level diet for Murres, followed by a strong shift to a predominantly Capelin‐based diet if available (Gulka & Davoren 2019), corroborated by> 94% Capelin delivered to Murre chicks in the study area (Davoren & Montevecchi 2003, Burke & Montevecchi 2008). As Murres provision chicks with a single food item at a time (i.e.…”

Section: Discussionmentioning

confidence: 68%

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Seabird species‐ and assemblage‐level isotopic niche shifts associated with changing prey availability during breeding in coastal Newfoundland

Jenkins

Davoren

2020

Ibis

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Shifting prey availability can lead to altered species interactions, indicated by variation in the dietary niche breadth and position of species within an assemblage. On the Newfoundland coast, annual inshore spawning migration of the dominant forage fish, Capelin Mallotus villosus, provides an excellent opportunity to investigate the influence of varying prey availability on dietary niche breadth and position among species. During June–August 2017, we investigated species‐ and assemblage‐level dietary responses to shifting Capelin availability of three Capelin‐eating, sympatrically breeding auk species, the Atlantic Puffin Fratercula arctica, Razorbill Alca torda and Common Murre Uria aalge. The diet of Leach's Storm Petrels Oceanodroma leucorhoa, which breed alongside the three auk species but are not known to rely on Capelin, was also examined to determine dietary shifts throughout breeding that were unrelated to Capelin availability. We quantified stable isotope ratios (δ15N, δ13C) in seabird blood components (plasma, cellular component) collected both before and after spawning Capelin arrived in the study area and compared isotopic niche breadth within a Bayesian framework. At the species level, auk trophic position increased and isotopic niche breadth narrowed after Capelin arrived, suggesting a more Capelin‐based diet. Simultaneously, trophic diversity of the auk assemblage, reflecting the extent of spacing among niches of species, decreased after spawning Capelin arrived inshore. Contrastingly, increased trophic position but broader isotopic niche breadth during higher relative to lower Capelin availability for Leach's Storm Petrel confirm that this species is probably not affected by the inshore arrival of Capelin, but instead that isotopic changes may be more related to a shift in breeding stage to chick‐rearing. Overall, our findings reiterate the importance of Capelin as a prey resource for breeding auks in coastal Newfoundland, but that the degree of reliance on Capelin varies among species, possibly allowing coexistence of these ecologically similar species. The findings highlight potential changing species interactions, such as increased competition, under declines in Capelin biomass.

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“…spawning) Capelin availability. This delineation was corroborated by Capelin biomass estimates from weekly hydroacoustic surveys (Gulka & Davoren 2019).…”

Section: Methodssupporting

confidence: 55%

Section: Discussionmentioning

confidence: 68%

Seabird species‐ and assemblage‐level isotopic niche shifts associated with changing prey availability during breeding in coastal Newfoundland

Jenkins

Davoren

2020

Ibis

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“…2°C; Davoren et al 2006), presumably to locate suitable spawning habitat (Davoren 2013b). Owing to the spatial predictability of capelin aggregations, on both a fine scale (spawning sites) and mesoscale (migratory routes), shearwaters may use memory to return to these specific and general areas, similar to other marine predators in the study area (Davo ren et al 2003, Gulka & Davoren 2019. If shearwater species use other features, such as distance to shore (a proxy of depth in our study area), to return to areas where capelin schools are predictably abundant and accessible throughout the water column, this might explain shearwater density and distributional patterns being more influenced by depth than fish density.…”

Section: Discussionmentioning

confidence: 99%

Associations of non-breeding shearwater species on the northeastern Newfoundland coast

Carvalho¹,

Davoren²

2019

Mar. Ecol. Prog. Ser.

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Prey aggregations are not uniformly distributed, driving predator species to aggregate in specific areas of high food availability. On the east coast of Newfoundland, capelin Mallotus villosus, a small forage fish, migrate inshore to spawn during the summer, providing an abundant food source for marine predators. During this period, non-breeding great shearwaters Ardenna gravis (GRSH) and sooty shearwaters A. grisea (SOSH), both long-distance migratory sea birds, aggregate in coastal Newfoundland, but it is unclear what drives their distributional patterns within this region. Using at-sea surveys, we investigated whether the density and distributional patterns of GRSH or SOSH were influenced by sea surface temperature, depth and fish (prey) density as well as the number of the other seabird species or other shearwater species (i.e. GRSH or SOSH). The presence and number of GRSH and SOSH were positively influenced by the density of the other sympatric shearwater species but were not influenced by the densities of other seabird species. These findings suggest that the benefits of foraging in close association may outweigh costs. Fish density was less important in explaining the presence and number of GRSH and SOSH than depth, as both species were mainly found together in shallow areas (< 50 m) along the coast. As fish density was primarily distributed in shallow areas, reflecting predictable locations of and migratory routes to capelin spawning sites, depth (or distance from shore) and the distribution of other shearwaters may provide important cues to locate regions of high prey availability in coastal Newfoundland.

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“…Individuals must respond quickly and favourably to these anthropogenic-induced changes for populations to persist. Phenotypic plasticity, or the variation in expression of a trait (i.e., physiological, morphological, behavioural) across environmental gradients [2], allows individuals to express traits that maximize fitness under varying environmental conditions [3,4] and in turn can help populations or species buffer against environmental change [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…generalist diet) may be comprised of generalist individuals, specialist individuals that feed on different prey types, or a combination of the two [13]. Under an increase in prey availability, generalist individuals would modify their foraging behaviour to take advantage of newly abundant resources, while the behaviour of specialist individuals should be unaffected [4,14]. Specialization, however, can be contextual, whereby a individual may be a specialist under stable conditions, but shifts to a generalist strategy when conditions change (released from competition, increase in prey availability) [5,15].…”

Section: Introductionmentioning

confidence: 99%

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

Maynard

Gulka

Jenkins

et al. 2021

Preprint

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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 eight 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.

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High individual flexibility in the foraging behavior of a marine predator, the common murre

Cited by 20 publications

References 89 publications

Seabird species‐ and assemblage‐level isotopic niche shifts associated with changing prey availability during breeding in coastal Newfoundland

Seabird species‐ and assemblage‐level isotopic niche shifts associated with changing prey availability during breeding in coastal Newfoundland

Associations of non-breeding shearwater species on the northeastern Newfoundland coast

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

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