Breeding biology of the Chilean Elaenia Elaenia chilensis, a long-distance migratory passerine in South America

CRISTIAN GOROSITO; V. R. CUETO; D. T. TUERO

ARDEA

NEDERLANDSE ORNITHOLOGISCHE UNIE

Año: 2022 vol. 110 p. 227 - 238

0373-2266

Studies examining breeding biology provideinformation about reproductive parameters, which are useful in formulatinglife-history theories. Although these studies have notably increased in theNeotropics in recent years, some gaps remain; thus, more research is needed tobetter understand life-history strategies of New World birds. Furthermore,research into the breeding biology of migratory birds is crucial to advance ourunderstanding of trade-offs between reproduction and migration in Neotropicalaustral migrant birds. Our aims were to describe in detail the breeding biologyof the Chilean Elaenia Elaenia chilensis,a long-distance Neotropical austral migrant, and to discuss currentlife-history theories for New World passerines. We monitored 113 nests duringfour consecutive breeding seasons (2014/2015–2017/2018) in theAndean-Patagonian Forest. The breeding season lasted 77 days and the nestingperiod, from egg laying to fledging, had a mean duration of 29.9 days. Meanclutch size was 2.4 eggs (range: 1–3) and decreased throughout the breedingseason. The incubation and nestling stages lasted c. 14 days each. Fledglingnumber also decreased as the season progressed. The mean ± SE daily nestsurvival rate was 0.960 ± 0.005, corresponding to an overall nest success of29.5%. Predation was the main cause of nest loss (61.1%). Reproductiveparameters of the Chilean Elaenia coincide with characteristics ofhigh-survival species that invest little in reproduction. Despite being along-distance migrant, its life-history strategy does not seem to be muchfaster than that of its tropical resident congeners. This might not support theresult reported in the Northern Hemisphere that migratory birds have a fasterpace of life than resident birds.