Nesting biology of the Hudson´s Canastero ( Asthenes hudsoni ) and the Bearded Tachuri ( Polystictus pectoralis ), two threatened and poorly known birds of the Pampas grasslands

TROFINO FALASCO, CLARA; DI GIACOMO, ADRIÁN SANTIAGO; ARANGUREN, MARÍA FLORENCIA; MARTÍNEZ AGUIRRE, TOMÁS; GRILLI, PABLO; PAZ, ESTEFANÍA LAURA; PIZZARELLO, MARÍA GIMENA; VERA, DAVID GUSTAVO; BERKUNSKY, IGOR

STUDIES ON NEOTROPICAL FAUNA AND ENVIRONMENT

TAYLOR & FRANCIS LTD

Año: 2022 p. 1 - 10

0165-0521

The accelerated rate of grasslands transformation has led to noticeable population declines ofmany grassland bird species. Although several species of the Pampas grasslands are of conservationconcern, the information on their nesting biology is generally sparse. During three consecutivebreeding seasons (2018?2019 to 2020?2021), we studied nesting attempts of two of themost threatened grassland bird species in central-eastern Argentina: the Hudson?s Canastero(Asthenes hudsoni) and the Bearded Tachuri (Polystictus pectoralis). We found 16 nests of Hudson?sCanastero and seven nests of Bearded Tachuri in natural grasslands. In both species, the modalclutch size was three eggs, and predation was the main cause of nest failure. Incubation andnestling periods lasted 15 and 11.5 days for the Hudson?s Canastero and 14.3 and 12 days for theBearded tachuri. Daily Survival Rates were 0.90 and 0.97, resulting in a cumulative survival of 4%for the Hudson?s Canastero and 39% for the Bearded Tachuri. We found that the breeding biologyof the two threatened grassland bird species is strongly tied to tall native grasslands and suggestthat both species could be sensitive to changes in breeding habitat, particularly in the grasslandvegetation structure.