Competitive Positioning as an Indicator of Nestling Survival in Red-cockaded Woodpeckers
ROBERT J. EPTING AND ROY S. DELOTELLE
Environmental Consulting & Technology, Inc., Gainesville, Florida
DeLotelle and Guthrie, Inc., Gainesville, Florida
Nestling behavior in five populations of red-cockaded woodpeckers (Picoides borealis) in peninsula Florida from 1997–2003 and 2007 revealed novel mechanisms and behavioral 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 blocking the 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 all broods 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 below the 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 satiate nests, those with elevated levels of aggressive behavior fledged significantly fewer young. Aggressive positioning behavior, fighting, and pecking occurred in Stage II and were an indication of later mortality. Blocking the cavity entrance by climbing the cavity wall and flipping over was observed in the majority of mortality broods in Stage II. Vigorous pecking occurred in a few Stage III broods and was an indicator of late stage mortality. These behavioral mechanisms have not been previously reported for Red-cockaded or other woodpecker species. The model we developed of competitive interactions at each nestling stage for red-cockaded woodpeckers is consistent with other species with competition and aggression in broods.
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