Saw-whet Owl

The northern saw-whet owl was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the other owls in the genus Strix and coined the binomial name Strix acadicus. Gmelin based his description on the "Acadian owl" from Nova Scotia that had been described and illustrated in 1781 by the English ornithologist John Latham in his multi-volume work A General Synopsis of Birds. The northern saw-whet owl is now one of five species placed in the genus Aegolius that was introduced in 1829 by the German naturalist Johann Jakob Kaup. The genus name is Latin for a screech owl, the word came from the Ancient Greek aigōlios meaning "a bird of ill omen". The specific epithet acadicus is from "Acadia", the name of a former French colony in Nova Scotia. Two subspecies are recognised: * A. a. acadicus (Gmelin, JF, 1788) – south Alaska, Canada, north, southwest USA and north Mexico * A. a. brooksi (Fleming, JH, 1916) – Haida Gwaii (formerly the Queen Charlotte Islands) (off British Columbia, Canada)

The northern saw-whet owl makes a repeated tooting whistle sound. Some say they sound like a saw being sharpened on a whetstone. These calls are usually produced by males searching for mates, so they can be heard more often beginning in January and continuing through the end of the breeding season in early July. Despite being more common in spring, they do vocalize year round. The advertising too-too-too call has been heard up to 300 meters away through forest. the Rapid call, Whine, Ksew call, Tssst call, Squeaks, Twittering call (similar to an American Woodcock), Guttural chuck, and begging calls of nestlings. Two additional calls only recorded in brooksi include the Transition Call and Alternate Whine. Non-vocal sounds such as bill snapping are used as a warning call by adults, juveniles and nestlings usually when approached up close or when in the hand.

The bird's habitat is coniferous forests, sometimes mixed or deciduous woods, across North America. Most birds nest in dense coniferous forests near wetlands during the breeding season, but may also breed in mixed-deciduous forests at the southern edge of their range in the eastern United States. Wintering birds prefer conifer stands or shrub thickets near water, but may occasionally be found in mixed-deciduous forest. They are secondary cavity nesters, meaning they do not make their own nest cavities but rather rely on naturally occurring holes or cavities excavated by other animals. Some are permanent residents, while others may migrate south in winter or move down from higher elevations. Their range covers most of North America south of the boreal forest, including southeastern and southcentral Alaska, southern Canada, most of the United States and the central mountains in Mexico. Some have begun to move more southeast in Indiana and neighboring states. Buidin et al. did a study of how far north the northern saw-whet owls breed and they found that they can breed northward of 50° N, farther than ever recorded before. Their range is quite extensive and they can even breed in the far north where most birds migrate from to breed. They are an adaptive species that can do well in the cold. There are two semi-isolated permanent populations in the eastern part of the United States. This first is a population along the West Virginia border in the Allegheny Plateau. The second population is in the higher elevations (>4000 ft) of the southern Appalachian Mountains of western North Carolina, eastern Tennessee, and southwestern Virginia. Although there are abundant populations in the Northern and Western Regions of North America, in some counties of North Carolina, it is currently listed as a threatened species due to a decline in suitable habitat. This is due to loss of boreal forests from hemlock woolly adelgid, logging, and pollution.

===Breeding=== Northern saw-whet owls lay about four or six white-colored eggs in natural tree cavities or woodpecker holes. Males will often sing from a nest site This type of mating is sequential polyandry. They compete with boreal owls, starlings and squirrels for nest cavities and their nests may be destroyed or the nestlings eaten by those creatures as well as nest predators such as martens and corvids. Saw-whet owls of all ages may be preyed upon by any larger species of hawks or owls, of which there are at least a dozen that overlap in range including Accipiter hawks, which share with the saw-whet owls a preference for wooded habitats with dense thickets or brush. In 2014 nesting northern saw-whet owls were found in breeding nest boxes in the Southern Appalachian mountains. This is the most southeastern known breeding area in the United States.

]] The northern saw-whet owl has vertically asymmetrical ears and different shapes of the ear openings. Because the sound reaches the ears at a different time and is of different intensity, the northern saw-whet owl can very precisely localize its prey. Such accurate sound localization allows it to hunt in complete darkness by hearing alone. A study by Beatini et al showed that the northern saw-whet owl had a possible frequency sensitivity of 0.7 to 8.6 kHz with the best sensitivity ranging from 1.6 to 7.1 kHz. This allows it to hunt in the dark purely by sound. The birds wait on a high perch at night and swoop down on prey. They mainly eat small organisms with a strong focus on small mammals in their diet. Swengel and Swengel (1992) reviewed ten studies that found northern saw-whet owls eating almost exclusively mammals (88% to 100%), with most of the mammals being rodents (85% to 99+%). Specifically in their Wisconsin study, the Swengels counted saw-whet owls as most often eating deer mice (Peromyscus; ~68% of captured prey), voles (Microtis pennsylvunicus and M. ochrogaster; ~16%), and shrews (~9%; Blarina brevicauda and Sorex cinereus). A similar study by Holt and Leroux (1996) in Montana found saw-whet owls eating more voles (60%) than other mammal species. Engel et al. (2015) also found in the saw-whet owl a strong preference for small mammals (89%), with 55% of prey being two species of voles. Holt and Leroux compared the eating habits of northern saw-whet owls to northern pygmy owls and found that they prey on different animals for their main food source, with the saw-whet owl's diet 98% small mammals, while for pygmy owls over one-third of their prey was birds. Their study concluded that these owls could adapt depending on the prey and also with the other predators in the areas where they live. Engel et al. (2015) in Chain O'Lakes State Park, Illinois, during the winter of 1987–88, compared northern saw-whet owls to long-eared owls. Engel confirmed the saw-whet owl's strong preference for small mammals. Their diet appeared varied in the winter, and was less tied to one mammal than was the long-eared owl; at times, northern saw-whet owls hunted larger prey, such as the meadow vole (M. pennsylvanicus). Other mammals preyed on occasionally include shrews, squirrels (largely chipmunks and red squirrels), various other mice species, flying squirrels, moles and bats. Also supplementing the diet are small birds, with passerines such as swallows, sparrows, kinglets and chickadees favored. However, larger birds, up to the size of rock dove (which are typically about 4 times as heavy as a saw-whet owl) can even be taken. On the Pacific coast they may also eat crustaceans, frogs and aquatic insects. Like many owls, these birds have excellent hearing and exceptional vision in low light.

An adult female northern saw-whet owl was found dehydrated and hungry within the wrapped branches of the Rockefeller Center Christmas Tree during its installation on November 16, 2020. The bird was discovered by workers who transported the spruce from Oneonta, New York to New York City. The feathered stowaway, named Rockefeller (Rocky), endured the three-day road trip and generated much public interest and media coverage. She was taken to a wildlife center for a check-up and nursed to full strength before being released on the grounds of the wildlife center in Saugerties, New York. Rocky gained more fame when Frontier Airlines announced that her image will be featured on the aircraft tails in their fleet.