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Abstract Animals that feed socially can sometimes better locate prey, often by transferring information about food that is patchy, dense, and temporally and spatially unpredictable. Information transfer is a potential benefit of living in breeding colonies where unsuccessful foragers can more readily locate successful ones and thereby improve feeding efficiency. Most studies on social foraging have been short term, and how long‐term environmental change affects both foraging strategies and the associated benefits of coloniality is generally unknown. In the colonial Cliff Swallow (Petrochelidon pyrrhonota), we examined how social foraging, information transfer, and feeding ecology changed over a 40‐year period in western Nebraska. Relative to the 1980s, Cliff Swallows in 2016–2022 were more likely to forage solitarily or in smaller groups, spent less time foraging, were more successful as solitaries, fed in more variable locations, and engaged less in information transfer at the colony site. The total mass of insects brought back to nestlings per parental visit declined over the study. The diversity of insect families captured increased over time, and some insect taxa dropped out of the diet, although the three most common insect families remained the same over the decades. Nestling Cliff Swallow body mass at 10 days of age and the number of nestlings surviving per nest declined more sharply with colony size in 2015–2022 than in 1984–1991 at sites where the confounding effects of ectoparasites were removed. Adult body mass during the provisioning of nestlings was lower in more recent years, but the change did not vary with colony size. The reason(s) for the reduction in social foraging and information transfer over time is unclear, but the consequence is that colonial nesting may no longer offer the same fitness advantages for Cliff Swallows as in the 1980s. The results illustrate the flexibility of foraging behavior and dynamic shifts in the potential selective pressures for group living.
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Developmental stage‐dependent effects of perceived predation risk on nestling tree swallows ( Tachycineta bicolor )
Abstract The risk of predation directly affects the physiology, behavior, and fitness of wild birds. Strong social connections with conspecifics could help individuals recover from a stressful experience such as a predation event; however, competitive interactions also have the potential to exacerbate stress. Few studies have investigated the interaction between environmental stressors and the social landscape in wild bird populations. In 2 years of field studies, we experimentally simulated predation attempts on breeding female tree swallows (Tachicyneta bicolor). At the same time, we manipulated female breast plumage color, a key social signal. Simulated predation events on tree swallows early in the nestling period reduced young nestlings' mass by approximately 20% and shortened telomere lengths. Ultimately, only 31% of nestlings in the predation group fledged compared with 70% of control nestlings. However, the effects of experimental manipulations were timing dependent: the following year when we swapped the order of the experimental manipulations and simulated predation during incubation, there were no significant effects of predation on nestling condition or fledging success. Contrary to our expectations, manipulation of the social environment did not affect the response of tree swallows to simulated predation. However, manipulating female plumage during the nestling period did reduce nestling skeletal size and mass, although the effects depended on original plumage brightness. Our data demonstrate that transient stressors on female birds can have carry‐over effects on their nestlings if they occur during critical periods in the breeding season.
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- Award ID(s):
- 2128337
- PAR ID:
- 10506145
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology
- Volume:
- 105
- Issue:
- 6
- ISSN:
- 0012-9658
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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