The Northern Aplomado Falcon was once a part of the dynamic and diverse wildlife community associated with our southwestern grasslands, but the species disappeared during the early 20th century. Restoring this species underscores the need to conserve important habitats. This effort is an ideal vehicle to promote creative solutions to problems associated with the Endangered Species Act, such as the innovative “Safe Harbor” permit, which has enrolled more than 2 million acres of potential Aplomado Falcon habitat in the interest of conservation.
Field studies are being conducted to document the current status of Aplomado Falcons and to understand their ecology. This effort provides a unique opportunity to study a new population as it begins to occupy both traditional and novel habitats. The Aplomado Falcon is an important “indicator species” for environmental quality due to its unique ecology and propensity to accumulate environmental contaminants. Addled eggs and tissue samples are being analyzed to gain knowledge of contaminant levels throughout the Aplomado Falcon’s range.
At the northern extent of the species’ range in Texas, the Aplomado Falcon is regaining its place as an integral part of the grassland ecosystem from which it has been absent for more than 50 years.
We again deployed the unique artificial nest structure that we developed to improve Aplomado Falcon nest success and productivity. To date, we have installed 101 structures throughout the range of the recovering South Texas population. Among the 28 known breeding pairs, 24 are using our artificial structures. Such approaches allow for the type of adaptive management necessary for a restoration program to work efficiently and effectively in the contemporary landscape.
Furthermore, we are working with the U.S. Fish and Wildlife Service to identify areas of habitat management need, particularly where brush has invaded grassland habitat not long ago occupied by breeding Aplomado Falcons. The initial phases of habitat management by Laguna Atascosa National Wildlife Refuge staff and cooperators have proven effective, and plans to continue and expand the management of falcon habitat are forthcoming.
Aplomado Falcon Releases
During the final release, we released 52 Aplomado Falcons from three sites in Texas: 30 falcons released at two sites at Mustang Island State Park and 22 on Laguna Atascosa National Wildlife Refuge land on South Padre Island. Forty-six of the 52 released falcons survived (88%). LightHawk and its team of volunteer pilots and one private pilot safely transported the falcons from our breeding facility in Boise to Texas, greatly reducing the stress on the falcons associated with extended travel time.
Two female falcons released on South Padre Island were fitted with satellite PTT transmitters in an effort to further understand falcon survival and dispersal in southern Texas. One of the falcons travelled north up the barrier islands approximately 50 miles from the release site. The second falcon has made several trips to falcon habitat on the mainland; however, she is currently on South Padre Island approximately 5 miles north of the release site. We also monitored one remaining falcon fitted with a PTT that was released in 2012 at one of the Mustang Island release sites. She has almost exclusively remained on the Texas coastal barrier islands, traveling as far as 100 miles north and 30 miles south. We will continue to monitor the movements and fates of these falcons throughout the coming months.
Aplomado Falcon Monitoring
We continued to focus our survey efforts in South Texas on determining occupancy at all known territories. We observed a total of 64 falcons. Of the 21 territories in the Matagorda Island National Wildlife Refuge survey area, 14 (67%) were occupied. In the Laguna Atascosa National Wildlife Refuge area, 14 out of 27 (47%) territories surveyed were occupied. Overall, while the number of occupied territories remained the same as the previous year, a decline in individual falcons, which includes unpaired adult female falcons at nest sites, reveals a continuing decline in the population first observed after the 2011 survey. We also continue to see juvenile males paired with adult females. While this illustrates recruitment of males into the breeding population, it also demonstrates a lack of available non-breeding adult males.
Although the area still continues to suffer from drought conditions, prey in the form of small birds and insects (e.g., cicadas) seems to remain in ample supply. While prey availability is not a concern, we are finding that loss of habitat to brush encroachment and potential development is a major concern in the Laguna Atascosa study area. The two most common woody plant species responsible for the encroachment of brush into falcon habitat are mesquite and huisache and could be closely related to the territory occupancy problems we are seeing in this part of Texas. Fortunately, the Refuge has begun to clear mesquite and huisache and re-open the grassland habitat in the Bahia Grande Unit of the refuge. Hopefully in short order, the size and scope of the habitat improvement projects will grow and have a positive impact on the falcon in southern Texas.
We also conducted Aplomado Falcon surveys in the Chihuahuan Desert area of west Texas and New Mexico. The previous falcon surveys revealed no nesting and only one individual adult falcon in each area. In the recent survey, one individual falcon was observed and one failed nesting attempt by a pair in southwestern New Mexico was documented. The surveys provide strong evidence that recovery of the Aplomado Falcon in the Chihuahuan Desert is unlikely.
We placed 14 new nest structures: two on San Jose Island, four on Matagorda Island and eight in the Laguna Atascosa area. We also serviced 30 nest structures to ensure they were suitable for use during the nesting season. Most structures required a minimal amount of maintenance. The new structure design has effectively ensured their use only by Aplomado Falcons and provides security from predation.
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 decreased because of drought and the conversion of grasslands to agriculture. Native grasslands, particularly at the Sueco area, continue to be converted to farmland with several territories still threatened by agriculture. We are working with state and federal agencies and conservation organizations in Mexico and the United States to address this issue. If the current trends in grassland conversion and reproductive success continue, the last known desert-dwelling Aplomado Falcon population in Chihuahua will become extinct during this decade.
|Project History||Notes From The Field|
|Publications and Data||Other Information|
|Photos and Videos|
|Video: Artificial insemination technique|