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Northern Aplomado Falcon Restoration – 2008 Report
(TPF) The Peregrine Fund — in Aplomado Falcon Restoration    Share

In 2008, the Aplomado Falcon restoration program had 34 Aplomado Falcons lay 156 fertile eggs that hatched, and 152 (97%) survived to release age. One of the ovulating falcons was a first-time layer. One falcon, which ovulated in 2007, did not lay in 2008. In addition to the captive eggs, three eggs were removed from a nest that was in jeopardy in South Texas and brought to the Boise facility. The three eggs hatched and all survived to release age. Including the wild eggs, 190 were fertile, 159 hatched, and 155 survived to release age.

New-laying Falcons

One falcon laid for the first time in 2007. This five-year-old female laid seven eggs. Three (43%) were fertile, three (100%) hatched, and three (100%) survived to release age.

Non-laying Falcons

Three breeding age (2+ years) female Aplomado Falcons did not lay. Two two-year-old females will remain paired with their males and should lay next year. A sixteen-year-old female, which laid eleven eggs in 2006, did not lay this year and will be repaired with a proven male for 2009.

Egg Production

Thirty-four Aplomado Falcons ovulated in 2008. Twenty-one were artificially inseminated, nine copulated and were artificially inseminated and four females (three because of old age and the fourth an imprint on display at the VMIC and therefore a single bird) did not copulate and no artificial inseminations were performed.

Twenty-one females were artificially inseminated and produced 222 eggs. One-hundred-five (47%) were fertile, 86 hatched (82%), and 84 (98%) survived to release age. Semen was obtained by stripping the paired males and was generally high quality.

Young Dying

Four young Aplomado Falcon chicks died in 2008. Three chicks hatched with unretracted yolk sacs, most likely from poor natural incubation because of the unusually cold spring. The yolk sacs were either reinserted into the abdominal cavity or removed but it appeared there were egg infections and antibiotics were administered. These chicks died a few hours after hatching. The fourth chick appeared normal until it arrived at the release site. At that time it had reduced control of its legs. The chick was euthanized and the necropsy revealed a trauma to the spinal column indicated by loose and easily manipulated vertebrate.

Young Retained for Breeding

Six young male Aplomado Falcons were retained for breeding. These birds were chosen based on genetic representation in the captive population. The males will be paired and placed in breeding chambers in the future. These young were retained to ensure we meet our proposed production goals.

Peregrine Falcon Incubation of Aplomado Falcon Eggs

Aplomado Falcon clutches are easily extended to more than eight eggs. This can greatly increase the potential production of the population. However, Aplomado Falcons only incubate three eggs at a time and natural incubation generally doubles hatchability. Our solution is to obtain natural incubation of Aplomado Falcon eggs from Peregrine Falcons. Incubation of Aplomado Falcon eggs by Peregrine Falcons is necessary to produce large numbers of young Aplomado Falcons on an annual basis.

Vitamin/Mineral Supplementation

Vitamin supplementation in the quail feed was similar to previous years. Additional vitamin E and biotin were added at the rate of 3.14 pounds and 0.86 pounds, respectively, to 1996 pounds of Purina Turkey Starter®. This supplementation provides the quail with 4 µgs. The vitamin E supplement causes similar circulating levels of vitamin E in the captive adult Aplomado Falcons compared to wild Aplomado Falcons. In addition we used Purina Turkey Starter® which contained 30 pounds per ton of marigold seeds. The marigold seeds contain high levels of beta carotene which enhances the skin color of the falcons. The two rations were fed to the quail at a ratio of two to one. Other vitamin/mineral supplements used in 1996 through 2007 were used in 2008. Dynamite Zoo Formula®, Dynamite Marketing Inc., was administered daily, at one-quarter teaspoon in the food items. This supplementation regime will be used prior to and during the 2009 breeding season.

Aplomado falcons on hack box


Release of Falcons

During the 2008 field season, a total of 149 Aplomado Falcons were released from three sites in New Mexico and four sites in West Texas. Our overall success rate for this year resulted in 88 (59%) falcons successfully reaching independence. A total of 1,542 captive-bred falcons have now been released in Texas and New Mexico, and during the previous five years, 444 of 650 (68%) falcons released became independent.

In New Mexico we continued our release efforts at the site on land administered by the Bureau of Land Management, White Sands Missile Range, and New Mexico State Lands Office and on the Armendaris Ranch (Engle, New Mexico). A total of 70 falcons were released in New Mexico in 2008; 32 at the aforementioned site and another 38 at two sites on the Armendaris Ranch. These falcons were released under the 10(j) Rule which designates the population in New Mexico and Arizona as a “Nonessential - Experimental Population.” Seventy-nine falcons were released at four sites in West Texas.
Mortality factors after release remained much the same as in previous years. This included premature dispersal and predation by Great Horned Owls and coyotes. Low condition of the falcons caused by high ambient air temperatures and subsequent dehydration and lack of appetite as well as adverse weather conditions, predominantly high wind, contributed to poor release success early in the season at two locations. We quickly responded to the problem by providing bath pans inside of the hack boxes and also fed pre-release falcons more quail mush. This presented problems later during release when falcons emerged from the hack box and showed little to no interest in the food available on the tower. The falcons fledged without making an association with the tower which led to premature dispersal. We adjusted to this problem by reinstituting removing food from the hack box and fasting the falcons the day prior to release to increase their hunger on release day. This worked very well and releases progressed as expected thereafter.

Depredating Peregrine Falcons were not a problem at release sites this year; however, southern New Mexico and West Texas received little to no rainfall between the months of October 2007 and June 2008 making it one of the driest winters and springs on record. This apparently had a huge negative impact on early nesting birds like raptors, and very few immature raptors were observed in the area during the hack season. These conditions most likely relate to the absence of Peregrine Falcons as depredating birds at hack sites this season, but we anticipate, once weather and range conditions improve in the area, Peregrines will again present a potential problem.

Nesting and Survey Results for Texas and New Mexico

Survey efforts in South Texas were focused on determining occupancy and productivity in all known territories as well as searching for falcons outside the current survey area; a total of 73 falcons were observed. This includes 31 territorial pairs and 11 individuals. Out of the 73 falcons sighted, we were able to determine if 35 (48%) were banded. We found 11 were un-banded and 24 were banded, of which 16 were identified. We surveyed 38 territories in South Texas of which 31 (82%) were occupied. Of the 15 territories in the Matagorda Island National Wildlife Refuge (MINWF) survey area, 14 (93%) were occupied. Eleven pairs attempted to nest and four were successful at fledging 12 falcons. Nest success was particularly low compared to the Laguna Atascosa National Wildlife Refuge survey area. Seventeen (74%) out of 23 territories surveyed in the Laguna Atascosa National Wildlife Refuge (LANWR) area were occupied; 14 pairs attempted to nest. One pair was still active at the completion of the survey and 10 pairs successfully fledged 26 falcons making this one of the highest productivity rates observed yet in the LANWR area at 2.0 fledglings per nest. Overall, occupancy was lower this year than in previous years with 31 out of 38 (82%) territories occupied; this is down from 2007 (91%). The occupancy rate for the LANWR area dropped from last year's 89% to 74%, and it appeared that a large amount of turnover occurred, especially in the male component of the population.

Of particular concern, aside from the number of unoccupied territories (n=4), was the presence of un-paired adult females on territories (n=2) and the presence of juvenile males paired with females on territories (n=4). Furthermore, the prey in LANWR wasn't very abundant, at least when compared to what we've seen before. The area had not received any rainfall between November of 2007 and June of 2008. Perhaps a lack of prey created a situation of unoccupied territories and apparent low condition in falcons occupying territories; nevertheless, fewer occupying pairs managed to fledge a considerable number of falcons despite the habitat and prey conditions earlier in the year. On MINWR, everything seemed normal with regards to falcons occupying territories and prey populations being substantial; however, nest depredation, even at artificial nest structures, depressed the observed productivity in this survey area. Likely predators include raccoons and Crested Caracaras.

Minimal survey work occurred in West Texas and New Mexico. Four territorial falcons were observed in New Mexico and five in West Texas. One pair fledged one falcon from a nest north of Valentine, Texas. In addition, we collected two addled eggs for contaminant analysis from an abandoned nest in one of the occupied territories in West Texas. Additional surveys were conducted on the King and Kenedy Ranches to check the nest structures and surrounding habitat, and included a road survey west of Raymondville. Overall, no falcons were observed during these surveys.

We placed six artificial nest structures in currently unoccupied habitat and four structures in existing territories as new additions or replacements. Currently, there are 63 nest structures available to falcons in South Texas.

Activity under Safe Harbor Permit

We conducted the first “take” activity under our Safe Harbor Permit since its inception in 1996. A construction project on Port of Brownsville property was approved and works begun prior to notification of The Peregrine Fund, putting a nesting pair of Aplomado Falcons in the middle of the project in jeopardy. After our biologists identified the problem, a meeting was held among all concerned parties. We determined the best course of action for all concerned, including the falcons, would be to pull (take from the nest) the falcons’ eggs and incubate them at our Boise facility. All three eggs were hatched and the young falcons were then sent to one of our West Texas release sites; two survived to independence. An additional, artificial nest structure was provided for the adult falcons approximately a quarter mile away from the construction project. Within days, the falcons had occupied this new structure and within several weeks were incubating another clutch of eggs.

Monitoring Remnant Populations in Mexico

Since 1996 we have monitored nest productivity of a small population of Aplomado Falcons in Chihuahua, Mexico. Since then the population has fluctuated with climatic conditions, particularly precipitation. In recent years the number of the population has also decreased due to conversion of grasslands to agriculture. During the 2008 season survey efforts focused on determining occupancy of known falcon territories within the Tinaja Verde and Sueco study areas. A total of 29 territories were surveyed; 17 (59%) were occupied. This is a decrease from 18 occupied territories observed in 2007. Twelve young fledged from 11 nests for a productivity rate of 1.09 young per occupied territory.

Native grasslands, in particular at the Sueco area, continue to be converted to farmland. During the last three years several territories have been converted to agricultural fields. We continue to work with state and federal agencies, and conservation organizations in Mexico and the United States in addressing this issue.
No falcons have drowned in water storage tanks equipped with these escape ramps. We currently have over 60 wildlife escape ramps operating within our study area. In 2008 we maintained existing escape ramps in the two study areas.

In collaboration with Miguel Mora at Texas A & M University, blood, addled eggs, and eggshells collected in Chihuahua and Veracruz were imported into the U.S. for analysis. We will determine organochlorine and inorganic element contaminant burdens and their potential association with egg failures and reproduction. During 2009 we plan to publish these results in a peer-reviewed journal.
During the 2009 season we will continue to monitor the status of the Aplomado Falcon in Chihuahua, Mexico; our focus will be occupancy surveys. We plan to promote grassland and Aplomado Falcon awareness with conservation groups and agencies in Chihuahua, Mexico.


During 2009 our captive breeding population will remain at 46 pairs. We plan to raise 100-150 falcons for releases at up to ten sites—five in New Mexico and five in West Texas. In collaboration with Miguel Mora environmental contaminants will be monitored at falcon territories in both the U.S. and Mexico.

Additional lands signed into the Safe Harbor program in 2008 totaled over 10,000 acres. Over 2.1 million acres are now enrolled in the Aplomado Falcon Safe Harbor in both South and West Texas. Because of the success experienced in reestablishing nesting pairs and the recent approval of 10(j) status for falcons in New Mexico and Arizona, release efforts are now being concentrated in New Mexico and West Texas. We will continue working with more land owners in order to incorporate additional suitable release and nesting habitat into the Aplomado Falcon Safe Harbor program.

The wild population in South Texas will continue to be monitored, and additional barred nest structures will be placed in both areas with existing falcons and in areas located between the nesting pairs on Matagorda Island and those to the south around Laguna Atascosa National Wildlife Refuge and Brownsville. We will document territory occupancy and productivity from established pairs. We also will inspect and maintain existing nest structures in South Texas. In West Texas and New Mexico we plan to do a systematic survey to locate nesting Aplomado Falcons.

Publications in progress include manuscripts on the importance of yucca grasslands to the Aplomado Falcon’s recovery, artificial nest structures and their usefulness as management tools, the effects of environmental contaminants on the falcon’s productivity, and factors influencing habitat use by grassland birds in Chihuahua. We also plan to develop a yucca grassland management strategy for land managers to implement.

In Chihuahua, Mexico, we will continue monitoring occupancy of the remnant population and promoting awareness of the Aplomado Falcon in the State. We will continue installing wildlife escape ramps to minimize falcon drownings. We plan to publish our work on environmental contaminants and grassland birds.

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