The Effect of Supplemental Feeding on the Known Survival of Reintroduced Aplomado Falcons: Implications for Recovery

The northern Aplomado Falcon (Falco femoralis septentrionalis) inhabited the inland and coastal grasslands of Texas, New Mexico, and Arizona until about 1930, when records of aplomados in the United States decreased. In 1986, the species was classified as endangered under the Endangered Species Act. Among other recovery efforts, 102 birds were released from 2006 through 2011, in its former range in New Mexico at the Armendaris Ranch in the south-central portion of the state. To promote their survival, an extended supplemental feeding program was conducted. From 2006 through 2008, supplemental food was provided daily, whereas from 2009 through 2011 food was provided every other day. Providing food once daily corresponded with an increase in the known survival of the aplomados, where known survival was obtained from the recorded observations of falcons at feedings, and the establishment of nearby nesting pairs. Unfortunately, this increase in known short-term survival and reproduction did not seem to lead to long-term survival or retention. This may be attributable to a lack of available prey throughout the Chihuahuan Desert as a result of ongoing drought, significant brush encroachment caused by historic over-grazing by cattle, the eradication of prairie dogs, and decreased summer and increased winter precipitation, as well as a possible increase in predation influenced by brush encroachment and the fact that the Armendaris Ranch sits at the northernmost edge of the aplomados' historical range. If the reintroduction on the Armendaris Ranch, and other areas with similar levels of prey, is to continue, our research supports the incorporation of an extended daily supplemental feeding program and efforts to improve access to prey, possibly by removing brush and restoring grasslands.