Why the American Kestrel (Falco sparverius) has a low success in natural nests? A study case in Argentina.

LÓPEZ, F. G.; OROZCO, P. M.; BERKUNSKY, I.; GRANDE, J. M.

Boise, virtual

Conferencia; Raptor Research Foundation 2021 Annual Conference; 2021

Raptor Research Foundation and The Peregrine Fund

Reproduction is the most important process in the life of any given species as it allows the persistence of its populations. The availability and quality of nesting sites, predation rates, inter/intraspecific competition and climatic factors among others are key factors to understand how species breeding success is shaped. The American kestrel (Falco sparverius) is a secondary-cavity-nester. They can adopt cavities on trees or artificial nest-boxes, but sometimes use nests of Monk Parakeets (Myiopsitta monachus) or Brown Cachalotes (Pseudoseisura lophotes). Since 2016, we followed 68 American kestrel natural nests (between 20/25 per year; 13 on cavities, 2 on Brown Cacholote nests, and 53 on Monk Parakeet nests) and 21 nest boxes (per year) in semiarid forests of central Argentina. The probability of breeding successfully was lower in natural nests (27%) compared with nest boxes (54%). %). Among natural nests, only breeding attempts in monk parakeet nests were successful (2016/17=20%, 2017/18=33%, and 2018/19=30%). Pairs breeding in natural nests had smaller clutch sizes than pairs breeding in nest boxes (2,4 ± 0,1 vs. 4 ± 0,1) and a smaller number of fledglings (1,6 ± 0,1 vs. 3,4 ± 0,2). Our results suggest that the presence of parakeet nests is critical for the breeding success of Kestrels using natural nests in our study area. Nest-boxes can help to reinforce the kestrel population in our study area, however, the effects of such reinforcement in other species should be carefully analyzed. Further research would be needed to disentangle this different apparent selection of nesting sites.