Aplomado banks into a dive 



birds. Some of the species in the 

 web, such as the meadowhrk, reside 

 in the grasslands year-round; others, 

 such as the chestnut-collared 

 longspur, arrive from northern 

 prairies in fall and depart in spring. 

 Both are important, but the pres- 

 ence of wintering birds is cru- 

 cial, particularly at the begin- 

 ning of the aplomado nesting 

 season. That's when the falcons 

 are storing fat to produce and 

 incubate their eggs. Thus, the 

 aplomado also depends on the 

 habitats that nurture the mi- 

 grants — some from as far away 

 as Alberta, Canada. 



Alberto Macias-Duarte, now 

 at the University of Arizona in 

 Tucson, studied the migrants 

 and other factors affecting aplo- 

 mado ecology at Tinaja Verde 

 and at the neighboring Coyamito Ranch. He ex- 

 amined the impact of bird abundance on falcon 

 breeding success, and showed how both were af- 

 fected by the severe drought that has gripped the 

 region since 1993. The drought, he suggests, has led 

 to such severe declines in the abundance of prey 

 birds that the falcons must travel extra distances from 

 their nests to forage. That demands more energy, 

 and exposes the young falcons to increased preda- 

 tion by ravens and others. 



Releases of aplomados on two cattle ranches in 

 west Texas began in 2002, but they are still in the 

 early stages. Unlike southern Texas, where food is 

 abundant and predation is the central issue, food may 

 be the biggest challenge for aplomados in the desert 

 grasslands. Time will tell whether west Texas, with 

 its vast open lands and vegetation so similar to that 

 of neighboring Chihuahua, will have enough doves, 

 meadowlarks, and other medium-size birds to sup- 

 port a breeding population of aplomado falcons. 



In the tall weeds of a derelict landing strip on the 

 far end of Matagorda Island, Texas, two of us 

 (Hunt and Cade) have joined Erin J. Gott and Paul 

 W. Juergens, both biologists for the Peregrine Fund. 

 Gott and Juergens are taking turns peering through 

 a telescope, attempting to identify the band num- 

 bers of a pair of aplomados perched on a low shrub. 

 The falcons are trying to decide whether to accept 

 the new nesting platform provided for them, or to 

 lay their eggs in an abandoned nest in a nearby bush. 

 The male glances up and spies a white-tailed hawk 

 casually soaring 400 feet above. Flashing off his low 



perch and climbing effortlessly at a steep angle, the 

 falcon begins to attack the much larger hawk. In a 

 matter of thirty seconds, the falcon is above the 

 hawk; he stoops sideways and down, as the hawk 

 flips over to present its talons. The hawk soars high- 

 er. The observers are spellbound. 



The hawk and his mate are neighbors of the nest- 

 ing aplomado pair. We see the female hawk take off 

 from a bush near her nest and join her mate; the two 

 birds soar high over their nesting territory. The male 

 aplomado intensifies his attack on both hawks, fly- 

 ing back and forth from one to the other, executing 



shallow, slashing stoops 

 over their backs, some- 

 times actually hitting 

 them. After several min- 

 utes our group begins tim- 

 ing the encounter, which 

 lasts about forty minutes; 

 never once does the little fal- 

 con stop attacking or set his 

 wings in a glide or soar. Run- 

 ning at fifteen to twenty times his resting metabolic 

 rate, he is consuming a huge amount of energy in the 

 continual, rapid beat of his wings. Nothing is more 

 important for survival and reproduction than de- 

 fending his nest and food supply, and his behavior 

 shows it. According to Juergens, the falcon and hawk 

 pairs fought relentlessly during last year's breeding 

 season, but both still managed to raise their young. 



In spite of such tenacity, aplomados have disap- 

 peared from much of their former range. That is 

 one reason the U.S. Fish and Wildlife Service list- 

 ed them as an endangered species in 1986, even 

 though the population in coastal eastern Mexico is 

 extensive. There is little immediate hope for an aplo- 

 mado comeback in much of the drier ancestral re- 

 gion to the north, because of the large-scale brush 

 invasion. But, as Enrique Baeza has learned, what 

 is good for aplomados is good for cattle ranching. 

 Biologists are pinning their hopes for the species on 

 that fact. The presence of this beautiful falcon is a 

 sign of prosperity, of landscape richness; its reap- 

 pearance is a sign that things are going well. 



If the aplomado makes a full recovery over the 

 long term, breeding aplomados will spread across 

 the Chihuahuan Desert grasslands of northern Mex- 

 ico and the southwestern U.S. For an increasing 

 number of us, the sight of two adult aplomados 

 perched together on the spike of a tall yucca, look- 

 ing out across a sea of yellow grasses for the move- 

 ment of an oriole or longspur, or racing together 

 toward a soaring, absent-minded redtail, is a re- 

 minder of how much our lives and livelihoods are 

 nourished by such natural processes. □ 



N AT UK A I insioRY May 2006 



