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Miscellaneous => Wild Life => Topic started by: BrokenWing on March 20, 2009, 04:25:58 am

Title: Aplomado Falcon
Post by: BrokenWing on March 20, 2009, 04:25:58 am
BrokenWing Chronicles
Aplomado Falcon (Falco femoralis)

The Aplomado Falcon is a bird of open country such as savanna and cerrado and is found from Central America throughout South America to Tierra del Fuego. In the northern and southern extremes of its range it is migratory and it is only seasonally present in Central America and Patagonia.

The overall population may be increasing as deforestation opens up new potential habitat.
Aplomado Falcon, Emas, Goiás, Brazil, April 2001 - click for larger image    Its pale supercilium extends behind the eye while its whitish throat and cheeks are separated by a dark malar stripe. There is a dark band across the belly and its thighs and lower underparts are rufous. The cere and legs are yellow.

In flight it shows a long tail for a falcon. This is blackish with five off-white bands and a white tip. In the fourth photo you can just make out the indicative white trailing edge to the wing.
Aplomado Falcon, Emas, Goiás, Brazil, April 2001 - click for larger image    Insects and birds form a large part of its diet and it normally spots its prey from a perch above the grasslands as in photos two and three. We normally saw pairs of Aplomado Falcons and they are reported to hunt in tandem with one bird flushing the prey while the other goes for the kill.

This Raptor is very slender, long-winged, and long-tailed, the size of a small Peregrine Falcon (length of 30–40 cm or 12–16 inches, average wingspan of about 90 cm or 36 in) but only half the weight (250–475 g or 9–17 oz). This resemblance in shape to the hobbies accounts for the former name Orange-chested Hobby. "Aplomado" is an unusual Spanish word for "lead-colored", referring to the blue-gray areas of the plumage. Spanish names for the species include Halcón fajado and Halcón aplomado.

Range, history, status

It ranges from northern Mexico and Trinidad locally to southern South America, but has been extirpated from much of its range, including northern and central Mexico except for a small area of Chihuahua. Until the 1950s it was found in the extreme southwestern United States, and reintroduction efforts are under way in West and South Texas. It may be returning naturally to southern New Mexico, as it was seen there every year from 2000 to 2005 and bred successfully in 2002[2]. Expansion of the reintroduction program to that area has met with criticism, because technically, all Aplomado Falcons in New Mexico are now classified as part of an "experimental" (reintroduction) population.


As such, while they are still legally protected from hunting, they are not protected by Endangered Species Act requirements to preserve habitat and the like. It is believed that mainly habitat destruction caused the species' (near-)disappearance from the US and hinders reestablishment of a wild breeding population; thus, a coalition of environmental groups is attempting to have full protection restored so as not to jeopardize the success of the expanding wild population and the reintroduction efforts

The Link.

 Current Listing Status:    Endangered
Date Listed:   Feb 25, 1986
Lead Region:    Southwest Region (Region 2)

States/US Territories in which the Northern aplomado falcon is known to occur:  Texas


Countries in which the Northern aplomado falcon is known to occur:  Guatemala, Mexico

The Link.

Threats and Reasons for Decline

    The Northern Aplomado Falcon was most commonly observed and collected in its U.S. range during the period 1870-1930. The falcon seemingly disappeared in the U.S. after the 1930s for reasons that largely remain a mystery. It is noteworthy to consider that the Aplomado Falcon was at the northern limits of its continental range in southeastern Arizona, southern New Mexico, and western and southern Texas; and, therefore, possibly vulnerable to small changes in habitat quality in this region.

    Severe overgrazing by domestic livestock and resultant brush encroachment in the Southwest, including Texas, has been most frequently implicated as the principal cause for the species' decline. Direct adverse effects of livestock grazing on potential falcon prey species have also been suggested as a possible cause. However, a recent review of the history of livestock trends and practices and other ecological factors in the Southwest in relation to the decline of Aplomados suggests different causes.

    In the late-1800s, large numbers of cattle were introduced onto Southwest grasslands occupied by Aplomados and their numbers remained high through the 1920s. Decades of overstocking had degraded desert grasslands by the 1920s. Recognition of this led to reductions in cattle numbers by the late-1920s and 1930s, particularly after passage of the Taylor Grazing Act in 1934. However, cattle stocking rates may have remained comparatively high in western and southern Texas well into the late- 1900s, since these ranges were mostly in private ownership and not subject to regulation by the federal act. At least at some Arizona and New Mexico sites where Aplomados occurred, brush did not extensively invade into grasslands until after the 1940s

    There is some evidence from early naturalists to support the notion that prairie dogs greatly expanded in the Southwest after the introduction of large cattle herds. Widespread and intensive grazing by cattle may have stimulated such an expansion, since prairie dogs require low-stature grassland habitats. Regardless of the cause, prairie dog numbers and acreages occupied were extremely high during the late-1800s through about 1920. A U.S. government campaign to control prairie dogs on publicly-owned lands in Arizona and New Mexico by use of strychnine poison began in 1912, and a similar state effort was initiated in Texas in 1915. Prairie dogs were substantially reduced through poisoning by the 1920s, their decline peaked in the 1930s, and they were virtually eliminated from southeastern Arizona and southwestern New Mexico by the 1940s and 1950s, respectively. This pattern of decline was probably mirrored in western Texas, except that prairie dogs were never completely eradicated and some populations have persisted there through the present time.

    Historic ranges of the blacktailed prairie dog and the Northern Aplomado Falcon in the Southwest, to include western Texas (prairie dogs never occurred during historic time in southern Texas), matched closely. This has led to speculation that habitat conditions generated by prairie dogs may have benefited Aplomado Falcons. It is reasoned that overall abundance, biomass, and catchability of avian and small mammal prey were greater inside prairie dog towns than in the surrounding grasslands. At least some potentially important avian prey species, such as meadowlarks, some plovers, Mourning Dove, Horned Lark, and others, seem to respond positively to grazing. Others, like the Borrowing Owl, are directly dependent on prairie dog borrows and other prairie dog habitat features for optimal nesting and rearing of young. Insects, reptiles, birds, and small mammals that used prairie dog colonies were probably easier to detect and catch by Aplomados than in surrounding grasslands, where herbaceous vegetation was denser and higher. In similar ways, cattle grazing may have provided short-term benefits to Aplomados.

    The natural coincidence of Aplomado and prairie dog distributions in the Southwest (outside southern Texas) and their simultaneous declines suggest that these events may have been related. Prairie dogs were eradicated by strychnine poisoning. This method of control was nonselective and undoubtedly killed other wildlife in the vicinity of dog towns. Aplomado Falcons could have been adversely affected by feeding on poisoned birds and mammals through relay toxicity. Relay toxicity also could have killed other raptors and ravens that provided nest platforms for Aplomados.

    It appears that a majority of historic encounters with Aplomado Falcons and high numbers and acreage of black-tailed prairie dogs coincided with historically high livestock stocking rates on Southwest grasslands (all between 1870 and 1920). Aplomado falcons and blacktailed prairie dogs, with overlapping distributions, disappeared from the Southwest landscape in the 1930s. Although, it is clear that prairie dogs were intentionally eradicated, causes of the Aplomados disappearance remain obscure. In Arizona and New Mexico, large scale mesquite and other shrub invasion into grasslands appears to have occurred after the demise of the falcon.

    Other factors could have affected the decline. Aplomado Falcons disappeared rapidly throughout their U.S. range, which suggest that a widespread phenomenon such as climate change could have been involved. Throughout the U.S. and Mexican range of the Northern Aplomado Falcon, the long-term, cumulative impact of cattle grazing to the recovery of this subspecies probably has been negative, since it eventually contributed to the evident degradation of desert and coastal grasslands. Grazing by cattle increases the spread of mesquite, diminishes water retention on rangelands through soil compaction and loss of herbaceous plant cover, and interrupts natural fire regimes by reducing plant fuel loads. In southern Texas, relatively high numbers of falcon eggs and specimens were collected by professional collectors during the early-1900s and possibly contributed to the disappearance of Aplomados in that region. Particularly in southern Texas and eastern Mexico, but also portions of the Aplomado's former desert range, large tracts of native grassland have been converted to pasturelands and croplands, thereby further reducing the extent and quality of Aplomado Falcon habitat.

    The pesticides DDT and DDE were not factors in the Alpomado's disappearance, since they were not introduced into the environment until the late-1940s. Even though these pesticides have been banned in the U.S. for over 30 years, heavy concentrations of DDT and DDE persists in potential prey species in the U.S. and northern Mexico. Furthermore, these pesticides are still in use in Mexico and other parts of Latin America. In eastern Mexico, DDT and DDE contamination has led to severe eggshell thinning in Aplomados. Birds and other organisms collected over the past decade from the lower Rio Grande, Laguna Madre, and other southern Texas locations contained heavy loads of PBCs, heavy metals, and organochlorine pesticides. Organophosphate pesticides are still heavily used throughout the range of the Aplomado Falcon, including in the U.S., and remain a serious threat to Aplomados. This group of pesticides has been linked directly to the deaths of thousands of songbirds, waterfowl, and raptors in Argentina and parts of the U.S. Other threats include direct loss of habitat from various forms of human development, secondary lead poisoning through ingestion of game birds (doves and quail), electrocution by improperly designed electrical transmission lines, and human disturbance in breeding areas.

The Link.