DOI: 10.5061/dryad.6djh9w17x
title: Social foraging and the associated benefits of group-living in Cliff Swallows decrease over 40 years

description: 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.
description: 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, .
 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.