Puerto Rico's endangered forest hawks

Two subspecies found only here

The Puerto Rico Breeding Bird Atlas describes the Broad-winged Hawk as a rare, endemic, non-migratory subspecies, and the Sharp-shinned Hawk as an endangered breeding resident subspecies tied to montane forest and shade coffee. Both were added to the federal endangered list on October 11, 1994, and DRNA Regulation 6766 lists them as critically endangered.

They share a 1997 recovery plan, amended in 2019. To be delisted, each must occupy at least 75% of its suitable habitat, have three stable or growing populations in protected areas, and have corridors between them; according to the latest reviews, no criterion has been fully met. Genetic evidence proposes raising the Sharp-shinned Hawk to a full species, Accipiter venator, though the federal Service has not yet adopted it.

Sharp-shinned Hawk: from a low of 19 to about 40 birds

In 1992 about 150 Sharp-shinned Hawks were estimated on the island. After Hurricane María the population fell to a low of 19 individuals. The Peregrine Fund has run annual surveys since 2015: from 2018 to 2022 they documented 22 to 37 adults a year, with 8 to 11 territorial pairs, and by June 2023, with the season still under way, they had recorded 41 individuals.

Today the strongholds are Toro Negro, Guilarte together with Casa Pueblo's Bosque La Olimpia, and Maricao. Carite had no detections from 2018 to 2022, and El Yunque only one in 2022. The subspecies lives in mature, dense-canopied montane forest, and most post-María locations were above 650 meters elevation. A fledgling can travel up to 28 kilometers from its nest, so populations may be less isolated than once thought.

Broad-winged Hawk: the northern karst as refuge

The Broad-winged Hawk population was estimated at 124 birds in 1997 and in 2010, and at 123 in 2016–2017. After María, a rapid survey of Río Abajo and its surroundings counted 19 to 34, plus 13 seen on other visits. In 2022, The Peregrine Fund covered 137 survey points and detected 43 birds in total, about a third of the pre-hurricane figure.

When listed, it was known from Río Abajo, Carite, and El Yunque. Today its core is the northern karst: in 2022, surveyors counted 20 birds in the Arecibo sector, 8 in Utuado, and 9 in Río Abajo State Forest, plus 4 in El Yunque and 1 in Guilarte; Carite, Maricao, and Toro Negro had no detections. Most suitable habitat lies on private land around Río Abajo, which makes conservation on private property essential.

What threatens them

Loss and fragmentation of mature forest, from agriculture, roads, power lines, and development, is the underlying threat. Hurricanes make it worse: María caused vegetation losses of 31% to 51% in its impact zone and hit the karst and Cordillera Central hard. Climate projections point to more intense hurricanes and less rain in the central mountains.

At the nest, Philornis fly larvae once caused up to 69% of Sharp-shinned Hawk nest failures at the fledgling stage in Maricao; Pearly-eyed Thrashers take eggs and rats take nestlings. Red-tailed Hawks prey on Sharp-shinned fledglings and nesting females and compete with Broad-winged Hawks: in a 2021 pilot study at Río Abajo, Red-tailed Hawks rose 82% while Broad-winged Hawks fell 82%.

How to recognize them

The Sharp-shinned Hawk is small, 25 to 36 centimeters long, with a small head, short rounded wings, and a long square-tipped tail. It flies with quick flaps and glides and slips between trees chasing small birds. Adults are blue-gray above and reddish below; females are noticeably larger than males.

The Broad-winged Hawk is about crow-sized, with a dark back, reddish chest, and broad tail bands; from below the wing looks pale with dark tips, and its voice is a thin whistle. The Red-tailed Hawk is much larger, with a rufous tail in adults, and is the one you see along highways and open country. The sound archive includes a Broad-winged Hawk recording made at Tanamá, Arecibo, in January 2023.

Nesting, management, and responsible birding

The Sharp-shinned Hawk builds a twig platform high in a tree or palm; the atlas found activity from November to June and in August, peaking in March. The Broad-winged Hawk builds a large stick nest; the literature gives January to July, and the atlas recorded a peak in April. Since 2018, The Peregrine Fund has removed clutches to hatch and release, prompting pairs to lay a second clutch, and treats nests against Philornis before hatching.

For birders: do not look for nests, do not play recordings to attract them, and do not publish territory coordinates. If you see one of these raptors, report it on eBird or to DRNA with a photo and a description of tail, wings, and behavior. Protecting mature forest, public and private, is the measure that helps both most.

Is the Puerto Rican Sharp-shinned Hawk endangered?

Yes. The Puerto Rican Sharp-shinned Hawk has been federally endangered since 1994 and is critically endangered under DRNA Regulation 6766. It fell to 19 individuals after Hurricane María, and 41 were counted in 2023.

How many Puerto Rican Broad-winged Hawks are left?

The most recent survey cited by the U.S. Fish and Wildlife Service detected 43 Broad-winged Hawks in 2022, about a third of the 123 estimated in 2016–2017. Most live in the northern karst around Río Abajo, Arecibo, and Utuado.

Where does the Puerto Rican Broad-winged Hawk live?

In closed-canopy forest, mainly in the northern karst: Río Abajo State Forest and nearby private lands in Arecibo and Utuado. In 2022 there were also detections in El Yunque and one in Guilarte.

How is the Broad-winged Hawk different from the Red-tailed Hawk?

The Broad-winged Hawk is much smaller, about crow-sized, with broad dark and pale tail bands, and tied to mature forest. The Red-tailed Hawk is larger, has a rufous tail as an adult, and is common along highways, towns, and open country.

What is the Philornis fly and why does it affect these hawks?

It is a fly whose larvae parasitize nestlings. At Maricao it once caused up to 69% of Sharp-shinned Hawk nest failures at the fledgling stage, and it has also been documented on a Broad-winged Hawk fledgling.

Why did Hurricane María hit these hawks so hard?

Because they depend on mature closed-canopy forest, and María caused vegetation losses of 31% to 51% in its impact zone, especially in the karst and Cordillera Central. The more generalist Red-tailed Hawk also appears to have benefited from the opened forest.