Body condition and abundance of endemic Passerines of Fernando de Noronha, Brazil

Habitat quality – resource availability and environmental conditions – affects body condition of birds, and when altered can lead to population decline and extinctions. Thus, we evaluated body condition and abundance of Noronha Elaenia (Elaenia ridleyana) and Noronha Vireo (Vireo gracilirostris) in anthropic and preserved areas in Fernando de Noronha, and sampled vegetation cover and food resource availability. We measured body condition (weight, fat, feather wear, ectoparasites, brood patch and cloacal protuberance) of 45 Noronha Elaenia and 52 Noronha Vireo, food resource availability (10 sample points of malaise trap and 20 of entomological umbrella) and vegetal cover (20 sample points). We observed that feathers were worn in the anthropic area for Noronha Elaenia (X2 = 15.2647; p = 0.009) and Noronha Vireo (X2 = 13.1024; p = 0.0042) and a greater number of Noronha Elaenia individuals with brood patches in the preserved area. The abundance of Noronha Elaenia and Noronha Vireo was greater in the preserved area (GLMM Chi2 = 9.9121, p = 0.001, GLMM Chi2 = 56.615, p <0.000, respectively), being associated with the vegetation cover. The anthropization process, with less food resource availability and vegetation cover in the anthropic area (t = -2.8959, df = 304.76, p-value = 0.004; F = 24.755, p = 0.001, respectively) may be leading to changes in body condition in Noronha Elaenia and Noronha Vireo. Our findings might assist with conservation and management actions, providing ecological information of endemic and threatened species exposed to habitat alteration.