Northern Aplomado Falcon

Falco femoralis septentrionalis

Description

The northern aplomado falcon is a distinctive bird of prey; dull red underparts, a gray back, a long and banded tail, and a striking black and white facial pattern distinguish adults. The lower breast sports a broad, blackish band or cummerbund with small, whitish crossbars. Feet are bright yellow and the sexes are similar, with males noticeably smaller than females. The aplomado falcon (Falco femoralis ) has been divided into three subspecies. The northern aplomado is the largest of the three, displaying a body length from 14.9-16.5 in (38-42 cm) and a wingspan from 40-48 in (102-122 cm). This is intermediate in size between the American kestrel and peregrine falcon.

The two other subspecies—F. f. pichinchae and F. f. femoralis —are found south of Central America and can be distinguished from the northern aplomado falcon by different dimensions, by the configuration of the abdominal bands, and by the relative darkness of their plumage.

Behavior

Aplomado falcons are predatory and feed on birds, insects, rodents, small snakes, and lizards. Although the bird feeds heavily on insects, smaller birds make up over 90% of the diet in terms of bulk. The northern aplomado falcon typically glides horizontally from tree perches in pursuit of small birds and insects. The approach ranges from a slow flapping flight to a full-powered sprint. Males and females sometimes hunt together: while the male hovers overhead, the female pursues the prey by hopping along the ground. Aplomado falcons have occasionally been observed stealing prey from other birds—a practice known as kleptoparasitism. Like most raptors, the species is territorial during the breeding season, likely remaining in the same area throughout the year in eastern Mexico. When nesting, they usually hunt close to their nest—within 546.8 yd (500 m). Courtship consists of aerial displaying by the male, and mutual soaring and diving by the pair.

These falcons do not construct their own nests but must depend on the availability of platforms and nests constructed by other hawks, ravens, or jays. In eastern Mexico, falcons nest during the dry season from January to June, producing eggs throughout this time. Most clutches of two or three eggs are laid in March through May. In the United States, most egg laying was recorded in April or May. The incubation period lasts about a month; nestlings fledge within 40 days of hatching and remain dependent for another month.

Habitat

This falcon prefers open rangeland and savannah—semi-arid grasslands with scattered trees and scrub growth. Associated trees are the oaks, acacias, or palms. In the United States, the species was found in the coastal prairies along sand ridges, in woodlands along desert streams, and in desert grasslands with scattered mesquite and yucca. In central Mexico the falcon has been found in open pine woodland. Individuals nest in trees with a density of 19 per 100 acres (40 hectares) and an average height of 29.5 ft (9 m). Taller trees provide better perches from which to spot prey. Similarly, sparser ground cover provides less cover for prey.

Distribution

The aplomado falcon has a wide geographic distribution that includes most of South America and parts of Central America. It has ranged into the desert grasslands and coastal prairies of the southwestern United States. The northern subspecies was first described from a specimen taken in 1887 near Ft. Huachuca, Arizona. The breeding range of this subspecies extended from Guatemala through central Mexico into southeastern Arizona, southern New Mexico, and southern Texas. Although the northern aplomado nested occasionally in New Mexico until 1952, it disappeared from most of its U.S. range by 1940. In Mexico, the breeding range encompassed the states of Tamaulipas, Chiapas, Campeche, Tabasco, Chihuahua, Coahuila, Sinaloa, Jalisco, Guerrero, Veracruz, Yucatan, and San Luis Potosí. In Guatemala, the subspecies was found along the Pacific slope of the Central American cordillera.

This falcon has been extirpated as a breeding species from the United States. It nests regularly only along the Gulf Coast of Mexico in portions of northern and central Veracruz, northern Chiapas, western Campeche, and eastern Tabasco. Population estimates are unavailable, but the species is considered uncommon and declining in its home range. The falcon's last known nesting in the United States occurred in Luna County, New Mexico in 1952. It has been irregularly sighted in southern Texas, New Mexico, and Arizona since then.

Rays of light in recent years have included the discovery, in 1995, of a falcon nest in Brownsville, Texas. The nesting pair of falcons was part of the Peregrine Fund's release program in either 1993 or 1994. This was the first new nest discovered in 54 years, and came as a delightful surprise to the release team, which had not anticipated the falcons released 1993-94 to nest until 1997 at the earliest. The status of the Central American population is unknown.

Threats

Habitat degradation is probably responsible for the disappearance of the subspecies from the United States. Thousands of acres of grassland habitat have been lost in the twentieth century because of a natural climatic drying trend and by conversion of prairie to agricultural uses. Much of the open grasslands of Arizona, New Mexico, and the Texas coastal plain have been gradually overgrown by shrubs and small trees; denser vegetation makes it difficult for the falcon to take its prey. In many places, permanent desert streams have been channelized and riparian habitats eliminated with catastrophic effects on local fauna. Along the coast, grazing cattle have damaged or destroyed wetlands where many bird species historically bred. A decline in numbers of smaller birds has meant a decline in falcon prey. Pesticide use in the United States probably contributed to the overall degeneration in habitat quality. Although now banned in the United States, the pesticides DDT and DDE continue to be used in Mexico. During a recent survey, falcons in Veracruz were found to be severely contaminated by pesticides. These pesticides disrupt the falcon's reproduction by causing extreme eggshell thinning. Nestings in Veracruz in the 1960s and 1970s have been observed to fail due to eggshell breakage during incubation. Experiences with the peregrine falcon show that pesticide contamination can lead to severe, rapid population declines.

Conservation and Recovery

Efforts are underway to reintroduce the northern aplomado falcon into its historic range in the southwestern United States. In 1983, the Peregrine Fund established a captive breeding population with seven birds at its facility in Santa Cruz, California. The hatching success rate has been poor, but through 1988 over 20 young had been reared.

Potential reintroduction sites have been surveyed. In Arizona, scientists have examined the Ft. Huachuca Military Reservation, the Research Ranch near Elvin, the San Pedro River National Wildlife Refuge (NWR), and the Santa Rita Experimental Range southeast of Tucson. In Texas, suitable habitat exists at the Laguna Atascosa NWR, the King Ranch near Kingsville, and the Attwater Prairie Chicken NWR near Eagle Lake. Researchers are examining sites on the White Sands Missile Range and on the Animas NWR in New Mexico.

The Peregrine Fund has released nestlings at the King Ranch and at Laguna Atascosa with some success. Scientists hope to improve the chances of these reintroduction efforts by using wild-caught nestlings from Mexico, as well as propagated birds. While assisting the reintroduction effort, the U. S. Fish and Wildlife Service (FWS) plans to recommend that suitable habitat in the southwestern United States be protected through acquisition or negotiation. Proper management techniques will need to be applied to maintain and restore a healthy grassland ecosystem. Such techniques would include prescribed burns and brush removal.

The goal of the 1990 Recovery Plan is to achieve a self-sustaining population of at least 100 breeding pairs in the United States. If this goal is reached and maintained for three years, the FWS will consider reclassifying the falcon to Threatened. The goal, however, is many years away.

Achieving a stable population of at least 200 breeding pairs in Mexico may require the elimination of DDT and DDE within the breeding range of the falcon.

As part of the Peregrine Fund's release program, 101 aplomado falcons had been released as of 1996; 72 of them had reached independence successfully. The Peregrine Fund plans to expand the program into New Mexico and Arizona.

Contact

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6911
Fax: (505) 248-6915
http://southwest.fws.gov

References

Hector, D. P. 1980. "Our Rare Falcon of the Desert Grassland." Birding, 3 (12): 92-102.

Hector, D. P. 1989. "Northern Aplomado Falcon Recovery Plan [Technical/Agency Review Draft]." U.S. Fish and Wildlife Service, Albuquerque.

Kiff, I. F., et al. 1978. "Eggshell Thinning and Organochlorine Residues in the Bats and Aplomado Falcons in Mexico." Proceedings of the 17th International Ornithological Congress. pp. 949-952.

New Environmentalism. "Private Stewardhip in Texas." http://newenvironmentalism.org/falcons.htm (12 July 2000).

U.S. Fish and Wildlife Service. 1990. "Endangered and Threatened Species Recovery Program: Report to Congress." U.S. Fish and Wildlife Service.