Identity and characteristics of feathers used as lining in Tree Swallow (Tachycineta bicolor) nests in Indiana and Ohio

Nest building represents an important part of parental investment and can significantly impact reproductive success in many bird species. Tree Swallows (Tachycineta bicolor) are secondary cavity nesters that readily accept nest boxes and construct basic grass nest cups lined with molted feathers from other bird species. We identified and described the characteristics of the feathers used as nesting materials by Tree Swallows in 4 different habitats in Indiana and Ohio. We monitored 41 nest boxes in 2017 and 53 nest boxes in 2018. After chicks fledged, we collected feathers from nests, counted them, and characterized them by size, color, and type. Brown, medium length (5–10 cm), and contour feathers were significantly more common than other types of feathers. We compared the prevalence and characteristics of feathers in nests across different habitat types, with results showing that nests located near lakes had significantly more feathers than those in agricultural habitats. We identified which species feathers belonged to using molecular techniques and morphological comparisons and found that they belonged to 26 species from 19 families and 11 orders: Galliformes, Anseriformes, Columbiformes, Gruiformes, Charadriiformes, Pelecaniformes, Accipitriformes, Strigiformes, Piciformes, Cathartiformes, and Passeriformes, including 20 previously unreported species within those orders. Thus, feathers used as nest lining by Tree Swallows are more diverse than previously reported. Feather identities from each habitat matched avian communities in those areas, suggesting that Tree Swallows are generalist feather collectors and that the number and characteristics of feathers used as lining depends on feather availability near the nesting site.We find and monitored Tree Swallow (Tachycineta bicolor) nests in eastern Indiana and western Ohio across 4 habitats (Agricultural, Prairie/early successional, Near lake, and Wetland), in June and July 2017 and May and June 2018. Once chicks had fledged, we collected all feathers from 41 nests in 2017 and 11 nests in 2018. To investigate the characteristics of feathers that were used as nest lining, we first counted all feathers from each nest. Then we categorized the size, type, and color of all feathers that were collected from nests. Size was measured with 1 cm precision and size categories were: 10–15 cm (large), and >15 cm (extra-large). Categories of feather type were contour, flight, down, and semiplume. To assign colors to feathers found in nests, we compared them against Ridgway (1886) color plates and categorized them as black, brown, gray, white, or other. We compared the number of feathers of each size, color, and morphological type in nests to determine which feathers were most used. In addition, we identified to which species feathers belonged to by: (1) extracting DNA from feathers, and amplifying and sequencing the cytochrome oxidase I gene; and (2) conducting morphological comparisons of feathers with museum specimens. Ridgway R. 1886. A nomenclature of colors for naturalists: and compendium of useful knowledge for ornithologists. New York (NY): Little, Brown, and Company; p. 141–178