Goals:
Establish a self sustaining population of Aplomado Falcons in the southwestern United States and Northern Mexico through captive propagation, release, and management with the ultimate goal of removing the species from the Endangered Species List.
Background:
The Northern Aplomado Falcon was last seen in the American Southwest in the 1950s, leaving its niche in the grassland ecosystem unfilled for decades. The Peregrine Fund began experimenting with breeding captive Aplomado Falcons and releasing them to the wild in the 1980s. The falcon was put on the U.S. Endangered Species List in 1986.
The recovery effort has been an ideal vehicle to promote creative solutions to problems associated with the Endangered Species Act. To provide suitable habitat, The Peregrine Fund has forged innovative Safe Harbor agreements in Texas that protect private landowners and provide 2.1 million acres of potential Aplomado Falcon habitat. In New Mexico, a 10(j) experimental, non-essential population designation for the endangered species has had similar results that extend beyond private land to lands managed by federal and state agencies.
Aplomado Falcon chicks are produced at the World Center for Birds of Prey and transported to Texas and New Mexico for release. More than 1,500 chicks have been released so far. Large-scale releases began in South Texas in 1993, where a self-sustaining population appears to be thriving, and expanded to West Texas in 2002 and New Mexico in 2006.
Recent Results:
- 107 young Aplomado Falcons were released to the wild from eight sites in New Mexico and West Texas, with more than 70% surviving to independence.
- 24 of 32 breeding pairs in South Texas used artificial structures, proving that they are a valuable management tool to help increase nesting success in the face of high frequency of predation and lack of suitable nest structures. We placed nine new nest structures: six on Matagorda Island and three in the Laguna Atascosa National Wildlife Refuge area and serviced 30 others to ensure they were suitable for use during the nesting season.
- Monitoring showed few breeding pairs in West Texas and New Mexico. We designed a study to determine what factors may be affecting reproduction in those areas of historic habitat.
Propagation
This season, 119 young were produced from 31 pairs of captive falcons. Of the 291 eggs laid, 175 (60%) were fertile. One hundred twenty-three (70%) hatched and 119 (97%) survived to release age. No nutritional or disease-related problems occurred.
Eleven young will augment the captive breeding population, now totaling 41 pairs. The current number of pairs will allow us to continue releasing between 60 and 80 falcons per year. We will continue to maintain as genetically diverse and productive a captive population as possible.
Releases
During the 2010 field season, 107 Aplomado Falcons were released from five sites in New Mexico and three sites in West Texas. Our overall success rate for this year resulted in 75 (70%) falcons successfully reaching independence.
In New Mexico, we continued our release efforts on land administered by Bureau of Land Management, White Sands Missile Range, and New Mexico State Land Office and on the Armendaris Ranch. One new site, named Beck Ranch, was activated on lands administered by Bureau of Land Management. A total of 67 falcons were released in New Mexico under the 10(j) Rule, which designates the population in New Mexico and Arizona as a “Nonessential- Experimental Population.” Forty falcons were released at three sites in West Texas located on private ranches.
Mortality factors after release remained much the same as in previous years. This included premature dispersal and predation predominantly by Great Horned Owls. We continued providing bath pans inside of the hack boxes and also fed pre-release falcons more quail mush to ensure their best condition possible for release.
The non-profit organization LightHawk and its team of volunteer pilots and one independent pilot safely transported the majority of falcons to New Mexico and Texas, greatly reducing the stress on the falcons associated with extended travel time.
Nesting and Survey Results
Aplomado Falcon nesting surveys are annually accomplished in the Chihuahuan Desert area of West Texas. Release efforts shifted to this historical habitat for the falcon in 2005. During spring surveys in 2009, we located 10 breeding pairs of falcons in this new recovery area, but 2010 survey efforts reflected a loss of eight of those pairs. As a result, all released falcons in the Chihuahuan Desert of New Mexico and West Texas during 2011 will be part of an in-depth telemetry study to discover what may have caused the falcons to disappear and whether releases should continue there in the future.
We continued to focus our survey efforts in South Texas on determining occupancy in all known territories. A total of 82 falcons were observed during a survey period of 17 April to 13 May, including 32 territorial pairs and 18 individuals. Of 40 territories surveyed in South Texas, 32 were occupied. Overall, the results mirrored those found in 2009. This indicates stability in the southern Texas population even during recent years of suboptimal weather and habitat conditions.
From winter 2009 to fall 2010 in South Texas, rainfall and habitat conditions improved dramatically after a very long, persistent drought that affected a large portion of Texas, especially along the Gulf Coast. Resulting prey populations were much better than what was observed in 2008 and 2009, especially in the Laguna Atascosa National Wildlife Refuge area area. We hope that these improved conditions will allow falcon occupancy to increase to 2005 and 2006 levels when habitat conditions were similar to those observed this year. Our modifications to new and existing nest structures have remedied the nest depredation problem detected in earlier years.
During a brief survey in March, and including observations during the release season, only two pairs of falcons were observed in West Texas. As a result, a telemetry study is planned for 2011 on all released young to determine why there are so few breeding pairs and whether releases should continue in historical desert ecosystems.
In New Mexico observations revealed only one falcon pair that consequently has not nested and is composed of a juvenile falcon and a sub-adult falcon. Several other sightings were reported throughout the state.
We placed nine new nest structures: six on Matagorda Island and three in the Laguna Atascosa National Wildlife Refuge area. We also serviced 30 nest structures to ensure they were suitable for use during the nesting season. The new nest structure construction included the modifications made in 2009.
Of the known pairs of Aplomado Falcons established in Texas, approximately one-third are located on properties enrolled in our Safe Harbor program. The Safe Harbor permit includes 57 counties in South and West Texas. We met with several private landowners in Texas and New Mexico to discuss the program and the possibility of additional release sites. In New Mexico, these discussions led to one new release site in 2010.
Monitoring Remnant Populations in Mexico
Since 1996, we have monitored nest productivity of a small population of Aplomado Falcons in Chihuahua, Mexico. This population has fluctuated with climatic conditions, particularly precipitation. In recent years the number of territorial pairs also has decreased due to conversion of native grasslands to agriculture.
We continue to work with state and federal agencies and conservation organizations in Mexico and the United States to determine organochlorine and inorganic element contaminant burdens and their potential association with egg failures and reproduction.
Of 28 territories monitored, we observed a marked decrease in the number of occupied territories from 25 per year from 1997-2004 to eight occupied territories in 2010. Only three nesting attempts observed, with one young fledging from those nests. This is the lowest productivity observed since the population was first discovered back in early 1990s.
Project Links:
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Location Note:
Southwestern United States and Northern Mexico
Species involved
- Aplomado Falcon — Falco femoralis
People involved in this project:
Cooperating Partners:
Combined Federal Campaign # 10639
