Sharp-shinned Hawk

Accipiter striatus

Gavilßn Pajarero, Gavilßn de Sierra

Audio 3
(D. Von Gausig, R. Rodrφguez Mojica)

IDENTIFICATION: A small forest hawk, dark blue-gray above, barred with rufous below. The wings are broad, and the barred tail is proportionately long, an adaptation for rapid turns and maneuvering as it chases small birds through the forest. The Puerto Rican subspecies (Accipiter striatus venator) has darker gray upperparts, darker tail barring and browner thigh feathers than most other subspecies of Sharp-shinned Hawk. Immatures are brown above and streaked below. Length: 25-34 cm.; weight: males 95 g., females 171 g.; wingspan 51-69 cm.

VOICE: The call is a rapid series of high-pitched, reedy, "kek" notes. Audio 3
(D. Von Gausig, R. Rodrφguez Mojica).

HABITAT: Currently restricted in Puerto Rico to five isolated mountain forest areas.

HABITS: Feeds primarily on small birds ranging in size from a tanager down to a hummingbird. Its long tail allows it to turn sharply as it flies after birds in dense vegetation. Prey is plucked at regular "butcher blocks." The adult female is larger than the male (as much as 50% larger), a characteristic called sexual dimorphism. This allows each sex to focus on different-sized prey species, as the birds partition the resources in their home range. In one study in Maricao, the average weight of birds that males captured was 13 g., compared to 45 g. for femalesÆ prey. Half of all prey brought to nests in that study were Bananaquits. The Puerto Rican subspecies of Sharp-shinned Hawk inhabits both natural forests and plantations (especially of the María tree, Calophyllum calaba). Each pair requires a home range of about 150 hectares. In December and January the male stakes out his territory in the morning by soaring and calling above the forest canopy. The male and female cooperate in January and February to build a stick platform nest just under the forest canopy, and will often improve on a nest used in previous years. When the white eggs are laid in March and April, the female spends most of her time incubating, and relies on the male for food. Average clutch size in one Puerto Rican study was 2.6 eggs, with an incubation period of 32 days. The young fledge and leave the nest about 30 days after hatching. But the adults continue to feed the young for a few more weeks. As they start to hunt on their own, the fledglings initially may have more success in capturing lizards than birds.

STATUS AND CONSERVATION: Common in North America, but the smaller, darker subspecies in Puerto Rico is on the federal endangered species list, with a total estimated population of only 154 individuals in 1992. The subspecies experienced a 40% decline in population from 1985 to 1992. Although the regeneration of natural forest since the early 20^th Century has helped this bird, recent deforestation due to construction of roads, power lines, and communication facilities, have reduced habitat. In addition, nest failures have been attributed to fledglings infested with bot fly larvae (Philornis sp.). Pearly-eyed Thrashers may prey on hawk nests directly, but also rob the nests of small bird species and thus reduce bird populations that the Sharp-shinned Hawk depends on. Sharp-shinned Hawks will occasionally kill young chickens, and as a result, farmers have persecuted the hawks. However, all birds of prey are currently protected by law. Coordination of forest management to protect and enhance the hawksÆ forest habitat is essential for their long-term survival in Puerto Rico, as is protecting active nest sites from disturbance. Eventually it may be possible to reintroduce Sharp-shinned Hawks to forest areas that they formerly occupied, if their habitat can be protected.

RANGE: Breeds from central Alaska and Canada south to central Mexico, and on the islands of Cuba, Hispaniola and Puerto Rico. The endemic subspecies in Puerto Rico is now found only in five public forest areas: Maricao, Toro Negro, Guilarte and Carite State Forests, and Caribbean National Forest (El Yunque). The highest density in recent surveys has been at the Maricao Forest, but you have to count yourself as very fortunate if you see one of these birds.

TAXONOMY: FALCONIFORMES; ACCIPITRIDAE; Accipitrinae. Very closely related species also breed in the Andes and in eastern South America.

References

Blidstein, K. L. and K. Meyer. 2000. Sharp-shinned Hawk (Accipiter striatus). No. 482 in The birds of North America (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.

Delannoy, C.A. 1997. Status of Broad-winged Hawk and Sharp-shinned Hawk in Puerto Rico. Carib. J. Sci. 33(1-2):21-33.

Delannoy, C.A. and A. Cruz. 1988. Breeding biology of the Puerto Rican Sharp-shinned Hawk (Accipiter striatus venator) Auk 105:649-662.

Delannoy, C.A. and A. Cruz. 1999. Patterns of prey abundance and use by male and female Puerto Rican Sharp-shinned Hawks. Carib. J. Sci. 35(1-2):38-45.

del Hoyo, J., A. Elliott, and J. Sargatal, eds. 1994. Handbook of Birds of the World, Vol. 2, New World vultures to guineafowl. Lynx Edicions, Barcelona.

Griffiths, C. S. 1999. Phylogeny of the Falconidae inferred from molecular and morphological data. Auk 116(1):116-130.

Johnsgard, P.A. 1990. Hawks, eagles, and falcons of North America: Biology and natural history. Smithsonian Institution Press. Washington, DC.

Liguori, J. 2000. Identification review: Sharp-shinned and Cooper's Hawks with an emphasis on a challenging wing-on perspective. Birding 32:428-433.

Pérez-Rivera, R, and R. Cotté-Santana. 1977. Algunas notas sobre los falconiformes residentes en Puerto Rico. Science-Ciencia 4:89-95.

Raffaele, H.A. 1989. A guide to the birds of Puerto Rico and the Virgin Islands. Princeton.

Raffaele, H.A. 1989. Una guía a las aves de Puerto Rico y las Islas Vírgenes. Publishing Resources, Inc., Santurce, PR.

Raffaele, H.A., J.W. Wiley, O.H. Garrido, A.R. Keith, and J.I. Raffaele. 1998. Guide to the birds of the West Indies. Princeton.

Rivera-Milán, F.F. 1995. Distribution and abundance of raptors in Puerto Rico. Wilson Bull. 107(3):452-462.

Scholz, F. 1993. Birds of prey. Stackpole Books, Mechanicsburg, PA.

Seutin, G. and V. Apanius. Gray Flycatcher predation on a hummingbird. Wilson Bull. 107(3):565-567.

Tossas, A. G. 2001. Two new avian host records for Ornithoctona erythrocephala (Diptera: Hippoboscidae) in Puerto Rico. Carib. J. Sci. 37:115-116.

US Fish & Wildlife Service. 1997. Puerto Rican Broad-winged Hawk and Puerto Rican Sharp-shinned Hawk recovery plan. U.S. Fish & Wildlife Service, Atlanta, GA.

http://www.macintech.net/

Raptors in general in Puerto Rico: http://netdial.caribe.net/~falconpr/

Sharp-shinned Hawk, Spanish text

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