Northern saw-whet owl

The northern saw-whet owl (Aegolius acadicus) is one of North America's smallest owl species, recognized by its distinctive call that echoes the sound of a saw being sharpened. This secretive bird inhabits a wide range across the continent, favoring dense coniferous forests but also found in mixed and deciduous woods.

Description and Identification

Adults typically measure between 17 and 22 cm in length with a wingspan of 42 to 56.3 cm. They possess a round, pale face with brown and cream streaks, yellow eyes, and a dark beak. The upper parts are brown or reddish with white spots, while the underparts are pale with darker markings. A notable feature is a distinct white, Y-shaped marking between their eyes. While plumage does not differ between sexes, females are generally larger than males. Interestingly, their flight feathers fluoresce a neon pink under UV light, a trait used for aging.

Habitat and Distribution

The northern saw-whet owl's range spans most of North America, extending from Alaska and Canada south through the United States and into central Mexico. They are most commonly found nesting in dense coniferous forests near wetlands, though they may also breed in mixed-deciduous forests at the southern reaches of their territory. Wintering birds seek out conifer stands or shrub thickets near water. While many populations are migratory, some are permanent residents, particularly in isolated areas like the Allegheny Plateau and the southern Appalachian Mountains.

Diet and Hunting Behavior

These owls are adept hunters, primarily feeding on small mammals, with a strong preference for rodents such as deer mice and voles. Their hunting prowess is enhanced by vertically asymmetrical ears, which allow for extremely precise sound localization, enabling them to hunt effectively by hearing alone in complete darkness. They perch on high vantage points at night and then swoop down on their unsuspecting prey. While mammals form the bulk of their diet, they will also consume small birds, and in coastal areas, may eat crustaceans, frogs, and aquatic insects.

Vocalization and Behavior

The characteristic call of the northern saw-whet owl, which gives it its name, is a repeated tooting whistle. Males are particularly vocal during the breeding season, which generally runs from January to early July, using these calls to attract mates. Researchers have identified at least 11 different vocalizations, including advertising calls, rapid calls, and whines. They are secondary cavity nesters, utilizing existing holes and cavities for their nests. The species exhibits sequential polyandry, where females may mate with multiple males in a single breeding season.

Conservation Status

Globally, the northern saw-whet owl is listed as a species of low conservation concern, with an estimated global breeding population of 2 million. However, habitat loss due to factors like logging and pollution has led to declines in certain regions, with local populations in areas like North Carolina and British Columbia facing threats. Efforts to mitigate habitat loss include the use of nest boxes, which the owls readily adopt.