Unspotted saw-whet owl

The unspotted saw-whet owl (Aegolius ridgwayi) is a small owl belonging to the subfamily Surniinae, native to the mountainous regions of Central America. Its taxonomy is subject to some debate, with some authorities recognizing three subspecies while others consider it monotypic. The species is closely related to the northern saw-whet owl, with some suggesting they could be a single species.

Physical Description and Identification

This owl measures between 18 and 21.5 cm (7.1 to 8.5 inches) in length and weighs approximately 80 to 90 grams (2.8 to 3.2 ounces). Its plumage is distinctive, featuring plain sepia brown on the upperparts, throat, and upper breast, contrasting with a plain cinnamon buff on the lower breast and belly. The wings are generally a grayer brown, and the tail is a darker brown. A notable feature is its brown facial disk, bordered by a narrow white rim, with whitish lores, chin, and 'eyebrows'. It possesses bright yellow eyes.

Distribution and Habitat

The unspotted saw-whet owl is found in humid temperate montane forests across Central America. The nominate subspecies inhabits areas from central Costa Rica into western Panama. Other subspecies are recorded in Mexico's Chiapas state, and in Guatemala and northwestern El Salvador. Its preferred habitat includes humid oak forests, cloud forests, and pine-oak forests, where it typically resides in the forest canopy but may also be found in more open areas with scattered trees near forest edges. Its altitudinal range varies by region, generally between 1,700 and 3,500 meters (5,600 to 11,500 feet).

Behavior and Ecology

As a nocturnal species, the unspotted saw-whet owl is primarily active at night. It is usually solitary outside of the breeding season and is believed to maintain territorial boundaries. Its flight is described as 'fluttery' and agile, characterized by quick wingbeats. The species is resident throughout its range, meaning it does not undertake long-distance migrations.

Diet

The precise diet of the unspotted saw-whet owl has not been extensively documented. However, it is presumed to subsist primarily on small mammals such as shrews and rodents. There is also an assumption that it preys upon birds and bats.

Breeding

Details regarding the breeding phenology of this owl are not well-known. The breeding season appears to occur at some point between March and July. Nests are typically found in tree cavities, which can be natural hollows or those previously excavated by woodpeckers. It is estimated that the female lays between five and six eggs.

Vocalization

The vocalizations of the unspotted saw-whet owl are distinctive. The male's territorial call is a whistled 'hoo hoo hoo…', repeated about ten times over three to five seconds. Females produce a high, slightly hissing 'ssirr'. Both sexes are capable of emitting a surprisingly loud shriek and a shrill, short chipper. These calls can be easily confused with the vocalizations of certain tree frogs from the genus Anotheca.

Conservation Status

The unspotted saw-whet owl was once assessed as Near Threatened by the IUCN but has since been reclassified as Least Concern as of 2004. Despite this designation, its population is estimated to be between 20,000 and 50,000 mature individuals and is believed to be declining. The primary threat is habitat loss due to widespread deforestation for timber, agriculture, and pasturing, particularly at lower elevations within its range. Mexican conservation authorities recognize the species as being in peril of extinction within that country.