Screech owl

Screech owls are typical owls (Strigidae) belonging to the genus Megascops, with 23 living species known at present, but new ones are frequently recognized and unknown ones are still being discovered on a regular basis, especially in the Andes. For most of the 20th century, this genus was merged with the Old World scops owls in Otus, but nowadays it is again considered separately based on a range of behavioral, biogeographical, morphological, and DNA sequence data.

"Screech owls" redirects here. For the TV series, see Screech Owls.

Screech owl
Temporal range: Miocene to present
Eastern screech owl, Megascops asio
Rufous morph
Gray morph
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Strigiformes
Family: Strigidae
Genus: Megascops
Kaup, 1848
Type species
Strix acio
Linnaeus, 1758
Species

Some 23, see text

Synonyms

Macabra Carlo Bonaparte, 1854

Screech owls are restricted to the Americas. Some species formerly placed with them are nowadays considered more distinct (see below for details). The related barn owl does, as well.

Long-tufted screech owl (Megascops sanctaecatarinae)

Description

Similar to other owls, the screech owl females are larger than the males of their species. They have a compact size and shape. They are small and agile, and about 7 to 10 inches tall and have a wingspan around 18 to 24 inches. They have prominent, wide-set feather tufts with bright yellow/green eyes. They have different brownish hues with whitish, patterned underside. This coloration helps them get camouflage against the tree bark.

Ecology and behavior

Screech owls hunt from perches in semiopen landscapes. They prefer areas that contain old trees with hollows; these are home to their prey, which includes insects, reptiles, small mammals such as bats and mice, and small birds. Screech owls have a good sense of hearing, which helps them locate their prey in any habitat. They also possess well-developed raptorial claws and a curved bill, both of which are used for tearing their prey into pieces small enough to swallow easily. They usually carry their prey back to their nests, presumably to guard against the chance of losing their meal to a larger raptor.

Screech owls are primarily solitary. During the late winter breeding season, however, males make nests in cavities, sometimes reusing abandoned nests of other animals, to try to attract females. The females select their mate based on the quality of the cavity and the food located inside. During the incubation period, the male feeds the female. These birds are monogamous, with biparental care. The young of most screech owls are altricial to semialtricial.[1]

Northern screech owls are found in eastern states, such as New Jersey and New York. The screech owls are named for their piercing calls. Their normal territorial call is not a hoot as with some owls, but a trill consisting of more than four individual calls per second given in rapid succession (although the sound does not resemble screeching or screaming). They also have a kind of "song" used in courtship, and as a duet, between members of a pair. Calls differ widely between species in type and pitch, and in the field are often the first indication of these birds' presence, as well as the most reliable means to distinguish between species. The distinctness of many species of screech owls was first realized when vastly differing calls of externally similar birds from adjacent regions were noted.

Evolution, taxonomy, and systematics

The genus was introduced by German naturalist Johann Jakob Kaup in 1848.[2] The type species is the eastern screech owl (Megascops asio).[3] The evolutionary relationships of the scops and screech owls are not entirely clear. What is certain is that they are very closely related; they may be considered sister lineages which fill essentially the same ecological niche in their allopatric ranges. A screech owl fossil from the Late Pliocene of Kansas[4] (which is almost identical to eastern and western screech owls) indicates a longstanding presence of these birds in the Americas, while coeval scops owl fossils very similar to the Eurasian scops owl have been found at S'Onix on Majorca.[5] The scops and screech owl lineage probably evolved at some time during the Miocene (like most other genera of typical owls), and the three (see below) modern lineages separated perhaps roughly 5 million years ago. Note, no reliable estimate of divergence time is known, as Otus and Megascops are osteologically very similar, as is to be expected from a group that has apparently conserved its ecomorphology since before its evolutionary radiation. Like almost all scops and screech owls today, their common ancestor was in all probability already a small owl, with ear tufts and at least the upper tarsus ("leg") feathered.

However that may be, the hypothesis that the group evolved from Old World stock[6] is tentatively supported by cytochrome b sequence data.[7][8] The screech owls also have a different placement of the procoracoid (less of an anterior incline) and coracoid bones compared to other New World owls.[9]

The splitting of Otus sensu lato
Pacific screech owl (Megascops cooperi)

While late-19th-century ornithologists knew little of the variation of these birds, which often live in far-off places, with every new taxon described a few differences between the Old and New World "scops" owls became more and more prominent. Namely, the scops owls give a whistling call or a row of high-pitched hoots with fewer than four individual hoots per second. This call is given in social interaction or when the owl tries to scare away other animals. The screech owls, though, are named for their piercing trills of more than four individual notes per second, and as noted above, they also have a kind of song, which is absent in the scops owls. A few other differences are seen, such as brown coloration below being common in scops owls and almost never seen in screech owls, but the difference in vocalizations is most striking.

By the mid-19th century, Otus was becoming identified as encompassing more than one genus. First, in 1848, the screech owls were split off as Megascops. Subsequently, the highly apomorphic white-throated screech owl of the Andes was placed in the monotypic genus Macabra in 1854. Gymnasio was established in the same year for the Puerto Rican owl, and the bare-legged owl (or "Cuban screech owl") was separated in Gymnoglaux the following year; the latter genus was sometimes merged with Gymnasio by later authors.

By the early 20th century, the lumping together of taxa had come to be preferred. The third edition of the American Ornithologists' Union (AOU) checklist in 1910, placed the screech owls back in Otus. Although this move was never unequivocally accepted, it was the dominant throughout most of the 20th century. In 1988, attempts to resolve this were made by re-establishing all those genera split some 140 years earlier at subgenus rank inside Otus.[10] Still, the diversity and distinctness of the group failed to come together in a good evolutionary and phylogenetic picture, and until the availability of DNA sequence data,t this could not be resolved. In the mid- to late 1990s, preliminary studies of mtDNA cytochrome b across a wide range of owls found that even the treatment as subgenera was probably unsustainable and suggested that most of the genera proposed around 1850 should be accepted.[7][8] Though some debate arose about the reliability of these findings at first,[11] they have been confirmed by subsequent studies. In 2003, the AOU formally accepted the genus Megascops again.[12]

The bare-legged owl was also confirmed as distinct enough to warrant separation in its own genus. Furthermore, the white-throated screech owl was recognized as part of an ancient lineage of Megascops – including also the whiskered screech owl and the tropical screech owl, which previously were considered to be of unclear relationships – and indeed its call structure is not too dissimilar from the latter. Its distinct coloration, approximated in the southern whiskered screech owl (Megascops trichopsis mesamericanus), is thus likely the result of strong genetic drift.

Additionally, a population of the tropical screech owl from northern Colombia has recently been proposed as the Santa Marta screech owl (Megascops gilesi) to the IOC.[13][14]

Species
Bare-shanked screech owl (Megascops clarkii)
Western screech owl (Megascops kennicottii)
Rufous- and grey-morph individuals of the tropical screech owl (Megascops choliba)

The genus contains 23 species:[15]

References
  1. Ehrlich, Paul R.; Dobkin, David S. & Wheye, Darryle (1988). The Birder's Handbook. A Field Guide to the Natural History of North American Birds. Touchstone, pp. 296–298, ISBN 0671659898/
  2. Kaup, Johann Jakob (1848). "Uebersicht der Eulen (Strigidae)". Isis von Oken (in German). Cols. 753-774 [765,769].
  3. Dickinson, E.C.; Remsen, J.V. Jr., eds. (2013). The Howard & Moore Complete Checklist of the Birds of the World, Volume 1: Non-passerines (4th ed.). Eastbourne, UK: Aves Press. p. 269. ISBN 978-0-9568611-0-8.
  4. Specimen UMMP 50982, a partial left coracoid from Fox Canyon: Ford (1966).
  5. Mlíkovský, Jirí (2002). Cenozoic Birds of the World, Part 1: Europe. Ninox Press, Prague.
  6. Johnson, David (2003). Owls in the Fossil Record. The owl pages.
  7. Heidrich, Petra; König, Claus & Wink, Michael (1995). "Molecular phylogeny of the South American Otus atricapillus complex (Aves Strigidae) inferred from nucleotide sequences of the mitochondrial cytochrome b gene" (PDF). Zeitschrift für Naturforschung C. 50 (3–4): 294–302. doi:10.1515/znc-1995-3-420. PMID 7766262. S2CID 28746107.
  8. Wink, Michael & Heidrich, Petra (1999). Molecular evolution and systematics of owls (Strigiformes). In: König, Claus; Weick, F. & Becking, J.H. (eds.) Owls: A guide to the owls of the world. pp.39–57. Yale University Press, New Haven. ISBN 0-300-07920-6
  9. Ford, Norman L. (1966). "Fossil Owls From the Rexroad Fauna of the Upper Pliocene in Kansas" (PDF). Condor. 68 (5): 472–475. doi:10.2307/1365319. JSTOR 1365319.
  10. Marshall, Joe T. & King, Ben (1988). Genus Otus. In: Amadon, Dean & Bull, J: Hawks and owls of the world: A distributional and taxonomic list. Proceedings of the Western Foundation of Vertebrate Zoology 3: 296–357
  11. "Proposal (#58): Elevate subgenus Megascops (New World Otus) to full generic status". South American Classification Committee. 2003. Retrieved 27 December 2017.
  12. Banks, Richard C.; Cicero, Carla; Dunn, Jon L.; Kratter, Andrew W.; Rasmussen, Pamela C.; Remsen, J.V. Jr.; Rising, James D. & Stotz, Douglas F. (2003). "Forty-fourth supplement to the American Ornithologists' Union check-list of North American birds" (PDF). Auk. 120 (3): 923–931. doi:10.1642/0004-8038(2003)120[0923:fsttao]2.0.co;2.
  13. Krabbe, Niels K. (October 2017). "A new species of Megascops (Strigidae) from the Sierra Nevada de Santa Marta, Colombia, with notes on voices of New World screech-owls" (PDF). Ornitología Colombiana. 16.
  14. "Proposed Splits/Lumps « IOC World Bird List". www.worldbirdnames.org. Retrieved 2018-01-28.
  15. Gill, Frank; Donsker, David, eds. (2017). "Owls". World Bird List Version 7.3. International Ornithologists' Union. Retrieved 23 December 2017.

Further reading
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