No abstract

Between 2013Between -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 6 0.5 eggs (mean 6 SD) (range ¼ 1-3; n ¼ 63), and the total nesting period was 34 6 2.5 days (mean 6 SD), with incubation and chick-rearing periods of 18 6 1.63 days and 16 6 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 ¼ 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.

Author's personal copy mo ¨gliche Geschlechtsunterschiede in der Brutpflege durch die beiden Eltern am Nest gelegt. Das Brutpflegevehalten wurde u ¨ber zwei Brutzeiten hinweg beobachtet und die Elterntiere gefangen, um ihre Ko ¨rpermaße zu bestimmen und Blutproben fu ¨r eine molekulare Geschlechtsbestimmung zu entnehmen. Wir fanden heraus, dass beim Braunru ¨cken-Sumpftyrann die Brutpflege eher von den Weibchen u ¨bernommen wurde: das Bru ¨ten selbst lag ausschließlich bei den Weibchen, und 74 % aller Aktivita ¨ten ums Bru ¨ten und Fu ¨ttern herum wurden ebenfalls von den Weibchen durchgefu ¨hrt. Ferner fanden wir a ¨ußere Geschlechtsunterschiede: fu ¨r Gro ¨ße und Gefieder waren sie eher kleiner, deutlich auffa ¨lliger jedoch in der Schnabelfa ¨rbung. Trotz der relativ kleinen Geschlechtsunterschiede war das Brutpflegeverhalten am Nest bei den Weibchen sta ¨rker ausgepra ¨gt; die Unterstu ¨tzung durch die Ma ¨nnchen war sehr unterschiedlich und korrelierte nicht mit der Gelegegro ¨ße. Diese Ergebnisse legen nahe, dass das soziale System der Gattung Pseudocolopteryx mo ¨glicherweise anders und unu ¨blich fu ¨r die u ¨brigen Tyranni ist.

No abstract