| Aegolius | |
|---|---|
 | |
| Boreal owl (Aegolius funereus) | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Strigiformes |
| Family: | Strigidae |
| Genus: | Aegolius Kaup, 1829 |
| Type species | |
| Strix tengmalmi [1] = Strix funereus Linnaeus, 1758 | |
| Species | |
See text | |
Aegolius is a genus of small true owls. The genus name is from Latin, aegolius, is a type of screech owl that was thought to be a bird of ill omen.
The genus Aegolius was introduced in 1829 by the German naturalist Johann Jakob Kaup with the boreal owl (Aegolius funereus) as the type species. [2] [3] The genus name is Latin for a screech owl, the word came from the Ancient Greek aigōlios meaning "a bird of ill omen". [4] In Greek mythology, Aegolius was originally a man whom Zeus transformed into an owl. [5]
The genus contains five species: [6]
Aegolius owls are small, stout, short-tailed, and broad-winged, with large, round facial discs. The species varies from 18 to 27 cm in length. These owls take mainly rodents and other small mammals as their prey, but also feed on birds, bats, insects, and other invertebrates according to what is available. They are dark brown or black above, and whitish or buff below, marked with streaks or spots in the two northern forms. The head is large, with yellow eyes and a well-defined facial disc. The flight is strong, agile, and direct. They breed in tree holes, laying several eggs. They have repetitive whistling calls in the breeding season.
Three of the extant species are restricted to the New World, but the boreal owl has a circumpolar range through North America, Eurasia, the Alps, and the Rockies. Essentially nocturnal woodland owls of temperate or colder climates; the two northern species breed in North America's coniferous forests, and the unspotted saw-whet owl and buff-fronted owl (Central and South America, respectively) are species of mountain, cloud, or oak forests. They are mainly resident birds, but the northern species at least sometimes move south or to lower altitudes in autumn. The movements are difficult to monitor due to the problems of detecting these nocturnal owls outside the breeding season, when they are not calling.
Aegolius owls have a very diverse mating system containing multiple strategies. Although there are five species within this genus, one of which is extinct, the majority of the information known about the mating system is based on research from the boreal owl (A. funereus) and the northern saw-whet owl (A. acadicus) in North America. [7] Both species have been shown to exhibit both monogamous and polygamous lifestyles with a focus on bigyny. [8] However, the boreal owl has been shown to exhibit biandry as well. [9]
Mate choice in this genus is largely related to auditory vocalizations (a form of sensory exploitation). A quiet species through most of the year, the northern saw-whet owl male produces a bell-like or “series song” advertisement call. [10] [11] Generally, it can be heard early morning or on bright nights from March – May (the breeding season) to attract females. [12] The calls are believed to be relatively different between individuals, suggesting they may play a role in individual identification by the females. [13] After pairing with a mate, vocalizations are very limited and appear to be related to territory or offspring defence. [14]
In contrast, the boreal owl produces a “staccato song” starting around dusk, and ending around midnight in the late winter and early spring. The call serves to attract females and becomes increasingly persistent as time without a mate passes. [15] [16] Some research suggests that unlike the Northern saw-whet owl, a variation of the male call persists after mating throughout the reproductive cycle for defense, aggression, or to convey information about prey. This suggests that vocalization may be used in this species beyond mate attraction and possibly as a contact call. [17]
Aside from vocalization, females in this genus may choose males based on nest or territory quality. For example, in boreal owls, the number and quality of nest holes or boxes defended by males is a factor in female reproductive effort. [18] The number and quality of nests appear to serve a direct benefit to females (direct benefit hypothesis), as it provides protection from predation, as well as access to food resources, as good nest quality can be indicated by access to prey (i.e. small mammals). [18] Female boreal owls' reproductive success can decline in polyterritorial polygamous situations, as females are unable to discriminate previously paired and unpaired males (also known as the deception hypothesis). It is also important to note that increasing polygamy levels leads to decreased reproductive success in secondary females. [18] Limited research has been conducted into mate choice of the Northern saw-whet owl in relation to territory quality. Some researchers suggest they follow a similar trend to boreal owls, where the quality of nests is a direct benefit to the female and therefore a determining factor. [19] Northern saw-whet owls' nest locations appear less linked to the availability of small mammals, as they have a greater variety of prey options and tend to be more nomadic after each breeding season. [19] [20]
Lastly, size of males may play a role in mate choice in some species. The males in this genus provide direct benefit to females such as protection, territory, and resources. As a result, large male size (and smaller female size) would theoretically be more advantageous. However, in the boreal owl, this is not the case. Females tend to be larger and heavier than the male mates they choose, some suggesting this is the result of the starvation hypothesis (selection acts on females to increase ability to withstand long periods of time without food in polygamous lifestyles). [21] Another theory suggests that females purposely choose short-winged, light males, as they would be able to hunt at lower energetic costs and compete for territory more efficiently than larger, long-winged individuals. [21] [22] This would provide the female with greater material benefits for her offspring. Reversed size dimorphism is also observed in northern saw-whet owls, but the differences are much more difficult to observe, as the species is smaller overall; the role of this in mate choice is unclear. [23]
Relating to the observed size dimorphism in males, most species compete for territory in this genus, as it indirectly relates to better female mates. [21] [22] [18] The intraspecific competition tends to be dependent on individual flight ability, individuals that can fly more efficiently and effectively tend to get better territory. [21] However, interspecific competition also plays a role. Species in this genus are often smaller than other owls that have similar ranges; as a result, they often are outcompeted for territory by other species. [7] [24] This is especially true in boreal owls, as their range overlaps with the much larger Ural ( Strix uralensis) and Eurasian eagle owls ( Bubo bubo). As a result, when these species are present, the boreal owl often mates with less desirable subdominant females. [24]
Parental care in the boreal and northern saw-whet owls is quite similar; females incubate and brood eggs, while males often provide protection, and resources such as food and nesting sites. [7] This trend likely applies across the species in this genus, as some species may be conspecifics (i.e. northern saw-whet and unspotted saw-whet owls). [25]
In boreal owls, the level of investment provided by the male is directly related to the level of parental care effort in brooding by the female. [26] Increased resources (i.e. food) provided by the male during the nesting stage increases female effort in brooding of the offspring. [26] This is similar to the differential allocation hypothesis, which suggests that females increase their reproductive effort overall when offspring are the result of ideal mates. Brooding behavior is key to the success of owl fledglings, so when males provide adequate food, females provide adequate care. [27] [26] Fewer or lighter individual fledglings are produced as polygamy rate increases and the amount of male effort becomes increasingly important in predicting female brooding effort. [28]
Information on parental care effort is limited on the northern saw-whet owl, and likely related to male provisioning rates, the extent, however, is unclear. Current research examines the effect of habitat loss on the male provisioning rates. [29]
The snowy owl, also known as the polar owl, the white owl and the Arctic owl, is a large, white owl of the true owl family. Snowy owls are native to the Arctic regions of both North America and the Palearctic, breeding mostly on the tundra. It has a number of unique adaptations to its habitat and lifestyle, which are quite distinct from other extant owls. One of the largest species of owl, it is the only owl with mainly white plumage. Males tend to be a purer white overall while females tend to more have more extensive flecks of dark brown. Juvenile male snowy owls have dark markings that may appear similar to females until maturity, at which point they typically turn whiter. The composition of brown markings about the wing, although not foolproof, is the most reliable technique to age and sex individual snowy owls.
The common goldeneye or simply goldeneye is a medium-sized sea duck of the genus Bucephala, the goldeneyes. Its closest relative is the similar Barrow's goldeneye. The genus name is derived from the Ancient Greek boukephalos, a reference to the bulbous head shape of the bufflehead. The species name is derived from the Latin clangere.
The rough-legged buzzard (Europe) or rough-legged hawk is a medium-large bird of prey. It is found in Arctic and Subarctic regions of North America, Europe, and Russia during the breeding season and migrates south for the winter. It was traditionally also known as the rough-legged falcon in such works as John James Audubon's The Birds of America.
The long-eared owl, also known as the northern long-eared owl or, more informally, as the lesser horned owl or cat owl, is a medium-sized species of owl with an extensive breeding range. The scientific name is from Latin. The genus name Asio is a type of eared owl, and otus also refers to a small, eared owl. The species breeds in many areas through Europe and the Palearctic, as well as in North America. This species is a part of the larger grouping of owls known as typical owls, of the family Strigidae, which contains most extant species of owl.
The dunnock is a small passerine, or perching bird, found throughout temperate Europe and into Asian Russia. Dunnocks have also been successfully introduced into New Zealand. It is by far the most widespread member of the accentor family; most other accentors are limited to mountain habitats. Other common names of the dunnock include: hedge accentor, hedge sparrow, hedge warbler, and titling.
The northern hawk-owl or northern hawk owl is a medium-sized true owl of the northern latitudes. It is non-migratory and usually stays within its breeding range, though it sometimes irrupts southward. It is one of the few owls that is neither nocturnal nor crepuscular, being active only during the day. This is the only living species in the genus Surnia of the family Strigidae, the "typical" owls. The species is sometimes called simply the hawk owl; however, many species of owls in the genus Ninox are also called "hawk owls".
The Eurasian pygmy owl is the smallest owl in Europe. It is a dark reddish to greyish-brown, with spotted sides and half of a white ring around the back of the neck. This species is found in the boreal forests of Northern and Central Europe to Siberia.
The northern saw-whet owl is a species of small owl in the family Strigidae. The species is native to North America. Saw-whet owls of the genus Aegolius are some of the smallest owl species in North America. They can be found in dense thickets, often at eye level, although they can also be found some 20 ft (6.1 m) up. Saw-whets are often in danger of being preyed upon by larger birds of prey. The northern saw-whet owl is a migratory bird without any strict pattern.
The boreal owl or Tengmalm's owl is a small owl in the "true owl" family Strigidae. It is known as the boreal owl in North America and as Tengmalm's owl in Europe after Swedish naturalist Peter Gustaf Tengmalm or, more rarely, Richardson's owl after Sir John Richardson.
The blue-headed vireo is a Neotropical migrating song bird found in North and Central America. There are currently two recognized subspecies that belong to the blue-headed vireo. It has a range that extends across Canada and the eastern coast of the United-States, Mexico and some of Central America. It prefers large temperate forests with a mix of evergreen trees and deciduous under growth.
The Carolina wren is a common species of wren that is a resident in the eastern half of the United States of America, the extreme south of Ontario, Canada, and the extreme northeast of Mexico. Severe winters restrict the northern limits of their range, while favorable weather conditions lead to a northward extension of their breeding range. Their preferred habitat is in dense cover in forest, farm edges, and suburban areas. This wren is the state bird of South Carolina.
The spotted owlet is a small owl which breeds in tropical Asia from mainland India to Southeast Asia. A common resident of open habitats including farmland and human habitation, it has adapted to living in cities. They roost in small groups in the hollows of trees or in cavities in rocks and buildings. It nests in a hole in a tree or building, laying 3–5 eggs. The species shows great variation including clinal variation in size and forms a superspecies with the very similar little owl.
The Ural owl is a large nocturnal owl. It is a member of the true owl family, Strigidae. The Ural owl is a member of the genus Strix, that is also the origin of the family's name under Linnaean taxonomy. Both its common name and scientific name refer to the Ural Mountains of Russia where the type specimen was collected. However, this species has an extremely broad distribution that extends as far west as much of Scandinavia, montane eastern Europe, and, sporadically, central Europe, thence sweeping across the Palearctic broadly through Russia to as far east as Sakhalin and throughout Japan. The Ural owl may include up to 15 subspecies, but most likely the number may be slightly fewer if accounting for clinal variations.
The elf owl is a small grayish-brown owl about the size of a sparrow found in the Southwestern United States, central Mexico, and the Baja California peninsula. It has pale yellow eyes highlighted by thin white "eyebrows" and a gray bill with a horn-colored tip. The elf owl frequently inhabits woodpecker holes in saguaro cacti; it also nests in natural tree cavities. It is nocturnal and feeds primarily on insects.
The buff-fronted owl is a small owl. It is found in widely separated areas in every South American country except French Guiana and Suriname.
The unspotted saw-whet owl is a small "typical owl" in subfamily Surniinae. It is found in Costa Rica, El Salvador, Guatemala, Mexico, and Panama.
The northern pygmy owl is a small owl native to western North America.
The Kentish plover is a small wader of the family Charadriidae that breeds on the shores of saline lakes, lagoons, and coasts, populating sand dunes, marshes, semi-arid desert, and tundra. Both male and female birds have pale plumages with a white underside, grey/brown back, dark legs and a dark bill; however, additionally the male birds also exhibit very dark incomplete breast bands, and dark markings either side of their head, therefore the Kentish plover is regarded as sexually dimorphic.
The northern boobook belongs to the family Strigidae and is a raptorial owl endemic to eastern and southern countries of Asia. The species was considered, until recently, a conspecific of Ninox scutulata or brown boobook, a species of similar distribution encompassing 11 subspecies. The species currently includes two subspecies, the migrant Ninox japonica japonica and the non-migrant Ninox japonica totogo. Despite being considered as the most common breeding owl in Japan, little research has been conducted on the species and subspecies and the taxonomic classification of N. j. totogo and N. j. japonica has been a subject of debate. There are no indications of significant decline in northern boobook populations and therefore its conservation status has been classified as least concern by the IUCN Red List.
| Authority control databases: National |
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