More is better: predator dilution effect increases Chilean Elaenia (Elaenia chilensis) nest survival

GOROSITO, C.A.; TUERO, D.T.; CUETO, V.R.

Journal of Ornithology

Springer Science and Business Media Deutschland GmbH

Año: 2023

Nest survival may be afected in several ways by predator-mediated interactions. According to the “predator dilution efecthypothesis”, the daily nest survival rate (DSR) can be density-dependent, because the probability of nest predation decreasesas the number of active nests increases. Additionally, parental activity may increase with clutch size, nest age, and after lowtemperature periods, while climatic components such as air humidity and moderate winds can increase odour dissipation fromnests. Consequently, predators can use these cues to locate nests, reducing the DSR. Determining such predator-mediatedinteractions is important to understand how multiple causes can afect avian reproductive success. Thus, we evaluated theefects of predation and predator-mediated interactions of abundance of active nests, parental investment and climate onannual and seasonal variations in DSR of the Chilean Elaenia (Elaenia chilensis), a long-distance migratory passerine thatbreeds in the Andean-Patagonian Forest. We monitored nests over four breeding seasons and modelled DSR for 86 nests. Themean ± SE DSR was 0.960 ± 0.005, corresponding to an overall nest success of 29.5%. DSR increased with the abundanceof active nests, but it did not vary among years or throughout the breeding season, nor was it afected by other variables.Hence, there was no infuence of parental investment and climate on predation. Instead, the increase in abundance of activenests towards the middle of the breeding season reduces the probability of predation per nest, resulting in greater ChileanElaenia nest survival, and providing empirical support for the “predator dilution efect hypothesis”.