Natal Dispersal of Aplomado Falcons in Chihuahua, Mexico

Abstract

The persistence of a species throughout its geographic range requires dispersal among its populations. The study of dispersal is particularly relevant for species whose geographic range has contracted, such as the endangered Northern Aplomado Falcon (Falco femoralis septentrionalis). We used Argos 5-g PTT-100 satellite transmitters to determine the movements of two wild Chihuahuan Desert Aplomado Falcons (one female and one male) from fledging to breeding (male), or transmitter failure (female), at 1062 d and 439 d of age, respectively. Both falcons dispersed from their natal territories 2–3 mo after fledging. These falcons then wandered between activity centers near historic breeding territories and some territories recently converted to farmlands. These two falcons also explored areas outside known breeding areas via some long-distance movements to areas of potential breeding habitat being converted to farmland. In 2 yr, movements of the male covered 7412 km2. This falcon nested unsuccessfully with an unbanded female in a vacant breeding territory 15 km from his natal site. His nesting attempt the following year yielded two fledglings. While a breeding bird, the male falcon had a home range of 200 km2. For 17 mo, the female falcon wandered through an area of 12,136 km2. The farthest distance she traveled from her nest site prior to transmitter failure was 154 km.