A morphometric sex determination model for adult greater roadrunners (Geococcyx californianus). (11th July 2014) - Montalvo, Andrea E.
ABSTRACT Little is known of the greater roadrunner's (Geococcyx californianus; roadrunner) ecology and many demographic questions are difficult to answer because of our inability to determine adult bird sex in the field. We collected measurements from live‐captured roadrunners of known sex in Fisher County, Texas, USA, and from roadrunner specimens from museums and university biological collections from 2003 to 2012 to develop a predictive logistic regression model for adult sex determination. We measured 433 adult birds of which 80% (n = 346) were randomly chosen to build potential models. Our best model included the variable estimate bill depth, which was found to be larger in males and correctly classified 80% of the birds. We validated the model with the remaining 20% of measurements (n = 87) and correctly identified the sex of 85% of the birds. Because this model incorporated roadrunners from across their range, it provides an easy, inexpensive, accurate, and field‐relevant methodology for sex determination of adult roadrunners at the point of capture. © 2014 The Wildlife Society.