Partial Depredations on Northern Bobwhite Nests
Document Type Article
Copyright 2012 University of California Press. Used by permission.
Partial clutch loss following a predation event is rarely studied in ground-nesting birds despite predation often being the leading cause of nest failure. Partial nest depredation occurs when predators attack but leave some eggs intact. Using continuous video monitoring, we documented a total of 372 initial predation events at nests of Northern Bobwhites (Colinus virginianus). From these, we observed a sample of partial nest predation events (n = 47). Partial predation events resulted in three outcomes: (1) The nest failed due to parental abandonment; (2) adult stayed with the nest, but clutch failed to hatch, usually due to further predation events; or (3) adult stayed with nest and the remaining eggs hatched, adding to the reproductive fitness of the adult. Most common predators causing partial depredations were ratsnakes (Pantherophis alleghaniensis and P. guttatus), kingsnakes (Lampropeltis getula), and fire ants (Solenopsis spp.). We used logistic regression and model selection methods to assess six cues that parents may use to determine the value of remaining offspring and resulting abandonment decision. Overall, nests with fewer eggs remaining after the predation event or those predated early in the incubation period were more likely to be abandoned; juveniles appeared more likely to abandon than adults. Future studies will be needed to confirm our findings of the relationships between cues and abandonment decisions, and video surveillance systems will be a necessary component of these studies.