Breeding biology of the Wren-like Rushbird (Phleocryptes melanops) in the southeast Pampas of Argentina

Abstract

Between 2013-2015, we conducted a study on the breeding biology of the Wren-like Rushbird (Phleocryptes melanops) in wetlands of the Pampas region, Argentina. The search for rushbird nests was conducted by several researchers walking into the wetlands, in three ways: by observing adults carrying material, through singing adults next to the nest or from the active search for nests in the vegetation. Nests were visited at intervals of 3-5 days. Of the 245 nests that we encountered (153 nests in 2013-2014 and 92 nests in 2014-2015), we found eggs in 97. The egg-laying period lasted almost 3 months (late Sept-late Dec). The mean clutch size was 2.7 ± 0.5 eggs (mean ± SD) (range = 1-3; n = 63), and the total nesting period was 34 ± 2.5 days (mean ± SD), with incubation and chick-rearing periods of 18 ± 1.63 days and 16 ± 0.50 days, respectively. From the total number of nests found, 43% of them were abandoned during building, 38% of nests were depredated, 14% of nests (n = 33) were successful, while 5% of nests were destroyed. Nest predation was higher during the incubation (80%) than during chick-rearing period (20%). The nesting success was on average of 23% (25% for the 2013-14 and 21% for the 2014-2015) for the entire nesting period. We also observed relatively higher plasticity than previously reported in relationship to vegetation used to fix nests (80% rushes, 20% other plants). Finally, we observed an abrupt termination of the reproductive period after desiccation of the wetlands; 90% of active nests failed (75% depredated and 25% abandoned) when the wetland was dried.