Competitive Positioning as an Indicator of Nestling Survival in Red-cockaded Woodpeckers

摘要

Nestling behavior in five populations of red-cockaded woodpeckers (Picoides borealis)in peninsula Florida from 1997-2003 and 2007 revealed novel mechanisms andbehavioral positioning of crossed, disproportionately long necks in all nestlings (Stage I,<10 days of age) and a behavior of cavity wall climbing, flipping-over and blockingthe cavity entrance from the other nestling in stage II broods (>10-17 days of age).Nest observations in Stage I showed that the crossed neck behavior occurred in allbroods of two or more, and facilitated dominant nestlings to beg sooner, reach higher,and to knock aside their smaller siblings, effectively controlling the central point belowthe nest cavity entrance. Stage II and III nestlings (11-17 and >18 days, respectively)were generally satiate in the cavity bottom on most occasions. Compared to satiatenests, those with elevated levels of aggressive behavior fledged significantly feweryoung. Aggressive positioning behavior, fighting, and pecking occurred in Stage II andwere an indication of later mortality. Blocking the cavity entrance by climbing thecavity wall and flipping over was observed in the majority of mortality broods in StageII. Vigorous pecking occurred in a few Stage III broods and was an indicator of latestage mortality. These behavioral mechanisms have not been previously reported forRed-cockaded or other woodpecker species. The model we developed of competitiveinteractions at each nestling stage for red-cockaded woodpeckers is consistent withother species with competition and aggression in broods.