Breeding biology of the masked gnatcatcher (Polioptila dumicola) in a native woodland of east-central Argentina

Abstract

Breeding biology studies provide valuable baseline information for assessing how species respond to habitat and ecological pressures. During three breeding seasons (2015 to 2018), we monitored 207 nests of the Masked Gnatcatcher (Polioptila dumicola), a resident species in the native woodlands of northeast Buenos Aires province that is susceptible to habitat changes. The breeding season extended from October to mid-February (~140 days). All nests were constructed in native tree species. One hundred and forty-five nests failed, with predation being the primary cause of failure (42%), followed by Shiny Cowbird brood parasitism (17%), and Philornis spp. ectoparasitism (6%). Successful nests produced ~2.4 fledglings on average. A maximum of seven nesting attempts were carried out by a single breeding pair in a single season. The predicted probability of nest survival, as per the quadratic age model was 34% for the 30-day nestling cycle, 83% for egg-laying, 9% for incubation, and 8% for the nestling period. This study contributes to the understanding of the life history traits of southern temperate bird species and provides valuable information on the breeding biology of a species sensitive to habitat modification in an increasingly threatened woodland.