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Different individual-level responses of great black-backed gulls
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.
Journal Article
Dinglehoppers and thingamabobs
\"Ahoy matey! I'm Scuttle. Welcome to my rock. Do you want to see my collection of treasures? You won't believe what they can do!\"--Page 4 of cover.
BOOK
How do gulls synchronize every-other-day egg laying?/?Como sincronizan las gaviotas la puesta de huevos en días alternos?
Increased sea-surface temperatures lead to increased egg cannibalism in Glaucous-winged Gulls (Larus glaucescens). Under these conditions, female gulls, which lay an egg approximately every 2 d, can synchronize egg laying with other females on an every-other-day schedule. Eggs that are laid synchronously are less likely to be cannibalized. The mechanism for synchronization has remained unknown. We studied the relationship between egg laying and mounting in a colony of Glaucous-winged Gulls on Protection Island. Washington, for clues to a synchronizing mechanism. We found that for an individual female an oviposition event reduced the likelihood of mounts for that day as compared to the day before, and that for sampled areas of the colony, total numbers of mounts and eggs laid occurred in an out-of-phase rhythm. These findings support the following conceptual model: early in the breeding season, individual females that have begun laying exhibit a daily alternation of higher and lower mounting activity caused by their natural 2 d oviposition oscillation. By social facilitation, these mounting oscillations of early layers synchronize mounting across the colony, including mounting events involving females that are not yet laying. Mount synchronization eventually leads to every-other-day egg laying synchronization. Received 10 February 2020. Accepted 4 August 2021.
Journal Article
Body Design or Behavior? What Explains the Performance of Slender-Billed Gulls in Salt Pans?
How animals perform vital tasks for their survival and reproduction is a crucial question to understand their current lifestyle and its evolution. Here we focus on the food acquisition by adult gulls feeding on small shrimp in salt pans in Camargue, France. The rate at which these gulls capture and ingest shrimp is extremely high. We calculate that this rate is high enough that it covers the energy requirement of an adult gull at its peak during the breeding season in less than 6 h. By analyzing slow-motion videos of feeding gulls, we were able to show that this performance is not achieved using particular, specialized morphological structures but rather by optimizing the suite of behaviors associated with locomotion, food capture, and food transport. This suite of behaviors is comparable to that used by two species of phalaropes that are not gulls but shorebirds, which also feed on prey captured at the saltwater surface. This raises the question of the similarity of these food acquisition behaviors in species belonging to different lineages, either due to their convergent evolution in the face of common environmental constraints or due to their maintenance during the diversification of lineages along the tree of life.
Journal Article
Bad badger
\"An eccentric badger ventures out to find his missing seagull friend\"-- Provided by publisher.
BOOK
Landscape, Environmental, and Socioeconomic Impacts of an Invasive Bird Species: The Yellow-Legged Gull
The yellow-legged gull (Larus michahellis) increased its population throughout the 20th century in its worldwide distribution area. In the Salinas de San Pedro del Pinatar, the population increased from having two breeding pairs in 1993 to 676 pairs in 2010 and from a wintering population of approximately 100–200 individuals in the 1980s to 1500–2000 individuals recorded in the 2010s, which has led to changes in habitats due to guano deposition, bird predation, incidents involving workers, and salt production. The objective of this study is to analyze the impacts of L. michahellis on the landscape, habitats, waterfowl, salt production, and workers, as well as to evaluate the effectiveness of control activities. Censuses of wintering L. michahellis have been carried out between 1990 and 2021, of nesting aquatic birds between 1994 and 2021, and nests and eggs of L. michahellis have been eliminated between 2000 and 2021. The result has been a decrease in pairs of L. michahellis, recovery of waterfowl populations, colonization of new bird species, absence of incidents with workers, and reduction in damage to salt production. Importantly, to reach a definitive solution, measures should be adopted to prevent L. michahellis from accessing the main sources of human food: urban solid waste dumps, aquaculture farms, and fish discards.
Journal Article