28-3 Sat Jan 2 Interspecific isotopic niche differentiation among Darwin’s finches in Santa Cruz Island, Galápagos Villegas, M*; Hobson , KA; Soos, C; Jiménez-Uzcátegui, G; University of Saskatchewan and Environment and Climate Change Canada, Saskatoon, SK, Canada; University of Western Ontario, London, ON and Environment and Climate Change Canada, Saskatoon, SK, Canada; University of Saskatchewan and Environment and Climate Change Canada, Saskatoon, SK, Canada; Estación Biológica Charles Darwin, Puerto Ayora, Galápagos, Ecuador mariana.villegas@gmail.com
Darwin’s Finches on the Galápagos Islands are a classic example of adaptive radiation and ecological segregation. Here we build upon this extensive foundation by using stable isotope analyses of feathers to examine the isotopic niche and trophic segregation among Darwin’s finches. We analyzed stable carbon, nitrogen and hydrogen values (δ13C, δ15N and δ2H) in wing secondary coverts from live birds (sampled in 2019) and museum specimens belonging to eight Darwin’s finch species from Santa Cruz Island. Insectivorous finches had higher δ15N and δ2H values and lower δ13C values compared to other guilds. Herbivorous finches had the largest isotopic niche followed by granivorous finches and lastly by insectivorous finches; although there was considerable overlap among guilds. Analyses proposed by Rossman et al. (2016), allowing for the use of three stable isotope dimensions, showed that when adding δ2H values in the description of trophic niche, insectivorous finches differentiate better from the other guilds. There was a significant difference in isotope values among habitats (i.e. dry, transition, humid zones and farms) only for δ13C values. Our study shows that even though some species are categorized to one guild (e.g., granivorous or insectivorous), dietary generalist species (those with a wide range of δ13C and δ15N values) dominate the bird community. Our results on isotope data indicate a greater dietary and ecological overlap among Darwin’s finches than previously described, especially among ground finches.