Social foraging and the associated benefits of group-living in Cliff Swallows decrease over 40 years
Data files
Feb 07, 2024 version files 48.69 MB
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Data_for_EM.xlsx
48.68 MB
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README.md
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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 1980’s, 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 among 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 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 are unclear, but the consequence is that colonial nesting may no longer offer the same fitness advantages for Cliff Swallows as in the 1980’s. The results illustrate flexibility of foraging behavior and dynamic shifts in the potential selective pressures for group-living.
README
README file for Data from Ecological Monographs, “Social foraging and the associated benefits of group-living in Cliff Swallows decrease over 40 years.” It is requested that any user of these data notify the corresponding author, Charles R. Brown, charles-brown@utulsa.edu. Each tab in the data file is keyed to a specific analysis in the paper, as described by the Table No. in the tab title. Note that for colony site, the same code is used for any given site across all analyses. Colony size refers to the number of cliff swallow nests active at the site. In some cases, SAS was used to concatenate variables in the Excel files to create new variables, and these variables do not show here. In cases where all data in an analysis are given in the paper (e.g., main Table 1, Table S7) or the information is descriptive (Table S1), they are not shown here.
If data are missing for a given cell, it is denoted with “.” (or in some cases by a blank).
Table S2-S4: Each row contains data for each scan at a colony on a given day. Contains (in this order) check (or scan) number, year, date within season (1 = 1 May), colony site (each site has the same designation in all years), weighted mean foraging group size (no. birds) on the scan; weighted average distance from colony (km) of foraging groups on the scan, sum of all group sizes (no. birds) per scan, site grouping (W= Whitetail, C = canal colonies), year-colony, percent of total residents in colony foraging on the scan, decade (E = 1984-1988, T= 2016-2022), year-colony-date, colony size (no. nests), circular mean angle for that scan, circular angular deviation for that scan.
Table S8: Each row is a watch at a single nest. Contains (in this order) year, date (1 = 1 May), colony site (same designation of a site in all years), nest identification number, year-colony, colony size (no. nests), time watch started, number of food deliveries, brood size (number of nestlings in nest), nestling age (in days), temperature (in degrees F), wind speed (km/h), and rad flux (lumens).
Table S9-S10: Each row is a bolus sample. Contains (in this order) year, sample number, number of insects in sample, decade (E = 1983-1988, T= 2016-2018), colony site (each site designated the same in all years), colony size (no. nests), year-colony, Shannon Index for that sample based on families.
Table S11-S12: Each row is a nest. Contains (in this order) nest identification number, colony site (each site designated the same in all years), colony size (no. nests), first egg date (1 = 1 May), clutch size (no. eggs), number of young survived, year, decade (E = 1984-1991, T = 2015-2022), year-colony.
Table S13: Each row is a nestling. Contains (in this order) year, colony site (each site designated the same in all years), colony size (no. nests), nest identification number, date of weighing (1 = 1 May), brood size (no. nestlings in nest), mass (g), year-nest.
Table S14-S16: Each row is an adult bird. Contains (in this order) year, sex, colony site (each site designated the same in all years), colony size (no. nests), body mass (g) during early period, body mass (g) during middle period, body mass (g) during late period, year-colony.