Nest defense behavior of Greater Roadrunners (Geococcyx californianus) in south Texas

Author(s): Helen T. Davis, Ashley M. Long, Tyler A. Campbell, and Michael L. Morrison

Published: September 2018

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The Greater Roadrunner (Geococcyx californianus) is a medium-sized predatory bird that occurs widely across the southwestern United States. Despite its prevalence in this region, studies examining the nesting and behavioral ecology of this species are limited. In 2015 and 2016, we examined relatively unknown aspects of roadrunner natural history by using infrared video cameras
to observe antipredator behaviors associated with Greater Roadrunner nest defense. Nest predation accounted for all nesting failures in our study. The Great Plains rat snake (Pantherophis emoryi) accounted for 70.0% of nest predation. We observed rat snakes entering the nest and consuming eggs or nestlings for .6 min before roadrunners flushed from nest sites. We also observed 53.3% of roadrunners actively defending nest sites from snake predators and zero defending nests from coyotes (Canis latrans), likely because of the predator size. Active defense sessions in our study lasted 1 min 20 s (95% CI 1 min 17 s) and consisted of 12.0 (95% CI 3.4) bill strikes per min of active defense. We observed no successful nest defenses because partial nest contents were lost during each event; however, .50% of predation events with an active defense
session resulted in preservation of at least one viable egg or chick, indicating nest defense was a valuable behavior. Examining nest defense behaviors in larger, predatory birds may elucidate risks and rewards associated with nest defense that may not be observed in studies focusing primarily on passerines.