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Boreal owl

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This article is about the owl species. For the women's national football team of Finland, seeThe Boreal Owls.

Boreal owl
Amherst Island, Ontario, Canada
CITESAppendix II(CITES)[2]
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Strigiformes
Family: Strigidae
Genus: Aegolius
Species:
A. funereus
Binomial name
Aegolius funereus
Subspecies

7, seetext

Range ofA. funereus
Resident
Non-breeding
Synonyms[3]
  • Nyctala tengmalmi(Gmelin, 1788)
  • Cryptoglaux tengmalmi(Gmelin, 1788)
  • Glaux funerea(Linnaeus, 1758)
  • Strix funereaLinnaeus, 1758
  • Strix tengmalmiGmelin, 1788

Theboreal owl(Aegolius funereus) orTengmalm's owlis a smallowlin the "true owl" familyStrigidae.It is known as the boreal owl in North America and as Tengmalm's owl inEuropeafter Swedish naturalistPeter Gustaf Tengmalmor, more rarely, Richardson's owl afterSir John Richardson.[3][4]

Due to the boreal owl's shyness and evasive reaction to human activities,nocturnal habitsand preferred inaccessibletaigaforest habitat, it is rarely seen by humans.

Taxonomy

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The boreal owl wasformally describedby the Swedish naturalistCarl Linnaeusin 1758 in thetenth editionof hisSystema Naturae.Linnaeus placed it with all the other owls in thegenusStrixand coined thebinomial nameStrix funerea.[5]The Eurasian scops owl is now placed in the genusAegoliusthat was introduced in 1829 by the German naturalistJohann Jakob Kaupwith the boreal owl as thetype species.[6][7]The genus name isLatinfor ascreech owl,the word came from theAncient Greekaigōliosmeaning "a bird of ill omen". The specific epithetfunereusis Latin meaning "funereal".[8]

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Congeners includenorthern saw-whet owl(A. acadicus),unspotted saw-whet owl(A. ridgwayi), andbuff-fronted owl(A. harrisii), all found in theNew World.[9]

Subspecies

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Sevensubspeciesare recognized:[7]

Fossil History

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Remains of the boreal owl dating back to thePleistocene erawere found in a cave in southern New Mexico.[10]Bones were found in a pueblo in north-central New Mexico that has been inhabited from around A.D. 1250 to the present.[11]

Description

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The boreal owl is small with a large head and long wings. Both sexes are similar in appearance, though females are larger. Males typically measure 21–25 cm (8.3-9.8 in) in length, with a wingspan of 55–58 cm (21.7-22.8 in), while females are larger – 25–28 cm (9.8–11 in) – with a wingspan of 59–62 cm (23.2-24.4 in). A female is heavier than a male bird and weighs 132-215 g (4.7-7.6 oz) compared to 93-139 g (3.3-4.9 oz) for a male bird.

Adult identification

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The plumage is brown above, with white flecking on the shoulders and whitish underparts with rust-colored streaks. Its large head has yellow eyes and an olive-brown crown with small white droplets and larger central spots. The dull whitefacial discis framed with a dark border and white “eyebrows” often described as giving the owl a "surprised" expression. The underparts are cream-white with russet-brown streaks, while the tail has olive-brown feathers with narrow bars.Flight feathersare dark olive-brown with contrasting white spots. Theprimariestypically have up to five rows of white spots, while the tail has three distinct rows of spots.[9]Unlike other owl species, these spots remain separated even when the tail is folded closely together.[12]The beak is light yellow, rather than dark like its relative thenorthern saw-whet owl.[13]The ears are asymmetrical in multiple bones, which enhances their hunting success. The boreal owl's flight is relatively noiseless and straight.[14]

Juvenile identification

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Juvenile of Aegolius funereus

Juvenile boreal owls, at about 3 weeks old, have a completely dull, chocolate-brown upperparts and underparts, with a dark brown facial disc bordered by black and white markings near the bill. Uponfledging,their plumage remains similar but with white markings on the neck, scapulars, flight feathers, and tail. They develop a broad white "X" between the eyes and distinct white streaks along the face, with cream-colored belly and flanks streaked in dark gray-brown.[9]

Moults

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Boreal Owls have two primarymoultingphases. ThePrebasic I moltoccurs around the age of two months, between August and September. It only affects the head, body, and wing coverts. The flight feathers, tertials, greater primary coverts, and tail are unaffected.[12]TheDefinitive Prebasic moltis also partial, affecting all of the head, body, and wing coverts, as well as the tail, but only a portion of the flight feathers, which are replaced in a specific order each year. Males in Idaho moult from June to October, while females do so from May to October.[12]

Vocalizations

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Vocalizations and related functions can be challenging to interpret because of their nocturnal and evasive lifestyle. Starting at one week old, young owls produce a harsh "peep" or "chirp" that softens after fledging. Comprehensive studies in North America has found 8 different types of vocalizations that play an important role in communication, mating, and territorial behaviour:[15][16]

  • ThePrimary Song- loud trill sung by males to attract females and establish territory[15]
  • TheProlonged Song- softer courtship melody sung by males from beginning of courtship to incubation to strengthen bonds[15]
  • TheDelivery Call- soft call by male to signal the transfer of prey to a female or young[16]
  • TheScreech- a load contact call made while flying or from a perch[15]
  • ThePeeping Call- soft vocalization by females throughout breeding to respond to males' calls
  • TheWeak Call- single note repeated rapidly from females in nest after hatching[15]
  • TheChuuk Call- harsh response call by females on male's territory[16]
  • TheHiss Call- defensive call by females when the nest is disturbed

Bill clapping is used as a protective sound by both adults and juveniles, and is frequently associated with vocal hiss. Young develop bill clapping at least one week before fledging. Adults reply with a bill clap when humans handle them or enter the nest cavity.[9]

Calls are similar in sound to the "winnowing" of the North AmericanWilson's snipe.[17][18]

Distribution and habitat

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The boreal owl breeds in denseboreal,subalpine forestas well asmixed woodland.The preferred habitats areold-growth forestsas they provide shelter from avian predators and an abundant number of preys.[19]Breeding habitats include boreal forests of black and white spruce,[19]birch and aspen across northern North America and thePalearctic,and in mountain ranges such as theAlpsand theRockies.Nests can be found in aspen and mixed forests, while individuals roost in conifers of about 6 meters high.[9]This species can travel long distances but are known to breed within 500 meters of their natal sites.[9]Males have a higher site fidelity than females and occupy stable year-long home ranges. However, northern populations maymigratesouth in response to snow depth and poor prey availability, but eventually return to their breeding grounds.[20][21][22]

Behaviour

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Breeding

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Egg, CollectionMuseum Wiesbaden

Boreal owls aremonogamousand raise a single brood once they reach one year of age. The breeding begins with a lengthy courtship process where males sing for up to 102 days, starting from mid-February to mid-April, depending on environmental factors like prey availability and weather.[23]The nest is usually a hole in a tree often made by a woodpecker, but the birds also readily usenest-boxes.Nesting period last for 28–36 days.[24]The clutch is usually 3-7 eggs which are laid at 2-day intervals. They are glossy white and measure 33 mm × 26 mm (1.3 in × 1.0 in) and weigh around 11.7 g (0.41 oz). The eggs are incubated only by the female beginning with the second egg and incubation lasts on average 29 days for the first egg and 2.6 days less for the last one.[9]They hatch asynchronously after 25–32 days. Females take care of the young and brood the nestlings for an average of 21 days. Food is brought by males during the first 3 weeks to the nest and female will tear apart the food for 2 weeks until young are able to eat unassisted. The young fledge after 28–36 days and become independent at 3 to 6 weeks outside the nest cavity.[25][9]Breeding densities fluctuate based on prey availability, ranging from 0.6 to 26 nests per square kilometer across different regions.[26][27]

Food and feeding behaviour

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This small owl eats mainlyvolesand othermammals(such asmice,chipmunks,othersquirrels,gophers,moles,shrewsandbats),[28][29]but alsobirdsas well as smallamphibians,[29]insects(such asbeetles)[29]and other invertebrates. In North America, they have been observed preying onsouthern red-backed voles,western heather voles,jumping mice,northern pocket gophersandnorthern flying squirrels.[28]Birds preyed upon includedark-eyed juncos,American robinsandcommon redpolls.[28]It is largelynocturnal,though in the northernmost parts of its range, it has to hunt during daylight because of the very short nights in summer. This species is asit-and-waitpredator meaning it does not pursue animals within 10 meters of its hunting perch. Their extreme asymmetrical skulls leads to sound localization in both horizontal and vertical directions and allow them to capture preys under snow and dense vegetation.[30]

Threats

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Biological resource use - timber harvest

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Logging activities have a negative impact on prey availability, foraging efficiency and suitable nesting sites.[31]Since the 1990s, significant population declines in northern Europe have been attributed toclear-cutting.Moreover, pesticides from agriculture and forestry effluents are damaging to the species' health.[32]The slow forest succession in spruce-fir ecosystems disrupts the recovery of critical habitat which impacts the species' ability to thrive.[19]Theblack woodpecker (Dryocopus martius)population decline in Eurasia has also led to a reduced number of nesting cavities.[33]

Predation

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Martenspecies (Martes spp.) andtawny owls (Strix aluco)are the predominant predators of boreal owl owlets and adult females at nest locations, with martens preying on 48% of Norwegian clutches.[34]Other predators includepine squirrels(Tamiasciurus hudsonicus),cooper's hawk (Astur cooperii),northern Goshawk,great horned owl(Bubo virginianus)andural owl(Strix uralensis).[35]Moreover,nuthatches(Sitta europaea) have been observed blocking the entrance of nests with mud, occasionally trapping females inside and starving them to death.

Mortality

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Boreal owl mortality rates vary by region and age. In Idaho, adult annual survival rate was 46%,[36]while in Finland, first-year males had a survival rate of 50%, and adult males 67%. Most fledgling males (78%) died before their first breeding attempt.[37]Overall, adult survival ranges from62% to 72%across studies.[38][39]Moreover, the average lifespan of breeding males is 3.5 years, and can go up to 11 years.Bandedboreal owls have been known to live up to 16 years.

Relationship to humans

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Owls have played an important role in myths and cultural belief, seen as both feared and worshiped creatures.[40]They are linked to death and seen as messengers between the living and the dead among Native Americans and the mountain tribes of Myanmar. In India, they are linked to cemeteries and are believed to keep the spirit of the deceased. However, they are associated to good fortune in Hindu mythology.[40]Furthermore, owls were important in art and symbolism in East Central Europe, especially the Pavlovian culture. Their appearance in art reflect a deep bond between humans and owls, based on shared environment and a strong "sense of place."[41]

Conservation status

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The current population trend is stable with 730,000 - 1,810,000 mature individuals: the species is currently listed underLeast Concernedunder CITES Appendix II, the EU Birds Directive Appendix I, and Raptors MOU Category 3.[1]Nevertheless, the species' lifestyle makes it hard to monitor the decline in some subpopulations. The USDA Forest Service Regions 1, 2, 3, 4 and 9 designated the species as a "sensitive species".[9]In Europe, systematic breeding surveys are being conducted in order to monitor its population status.[42]Nest boxes are implemented to create suitable nesting sites and ensure reproductive success.[19]The preservation of old-growth forests - with selective tree harvest to allow tree removal while maintaining suitable habitats[9]- and protectionblack woodpeckers(Dryocopus martius), that provide nesting cavities, are mandatory for the species' long-term survival.

References

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  1. ^abBirdLife International (2021)."Aegolius funereus".IUCN Red List of Threatened Species.2021:e.T22689362A201898946.doi:10.2305/IUCN.UK.2021-3.RLTS.T22689362A201898946.en.Retrieved12 November2021.
  2. ^"Appendices | CITES".cites.org.Retrieved2022-01-14.
  3. ^ab"Aegolius funereus".Avibase.
  4. ^Beolens, Bo; Watkins, Michael (2003).Whose bird?: Men and women commemorated in the common names of birds.London: Helm.ISBN0713666471.
  5. ^Linnaeus, Carl(1758).Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis(in Latin). Vol. 1 (10th ed.). Holmiae (Stockholm): Laurentii Salvii. p. 93.
  6. ^Kaup, Johann Jakob(1829).Skizzirte Entwickelungs-Geschichte und natürliches System der europäischen Thierwelt(in German). Vol. c. 1. Darmstadt: Carl Wilhelm Leske. p. 34.
  7. ^abGill, Frank;Donsker, David;Rasmussen, Pamela,eds. (January 2022)."Owls".IOC World Bird List Version 12.1.International Ornithologists' Union.Retrieved2 March2022.
  8. ^Jobling, James A. (2010).The Helm Dictionary of Scientific Bird Names.London: Christopher Helm. pp.33,166.ISBN978-1-4081-2501-4.
  9. ^abcdefghijHayward, G. D.; Hayward, P. H. (2020-03-04), Billerman, Shawn M. (ed.),"Boreal Owl (Aegolius funereus)",Birds of the World,Cornell Lab of Ornithology,doi:10.2173/bow.borowl.01,retrieved2024-10-14
  10. ^"Google Scholar".scholar.google.Retrieved2024-10-14.
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  12. ^abcHandbook of the birds of Europe the Middle East and North Africa: the birds of the Western Palearctic.Oxford [u.a.]: Oxford University Press. 1977.
  13. ^Bull, Farrand (1994).National Audubon Society Field Guide to North American Birds: Eastern Region.New York: Alfred A. Knopf. p. 554.ISBN0-679-42852-6.
  14. ^Svensson, Lars; Mullarney, Killian; Zetterström, Dan (2009).Collins Bird Guide(2nd ed.). London: HarperCollins. p. 226.ISBN978-0-00-726814-6.
  15. ^abcdeMeehan, R. H. (1980). Behavioral significance of Boreal Owl vocalizations during breeding season. Master's Thesis, Univ. Alaska, Fairbanks.
  16. ^abcBondrup-Nielsen, S. (1984)."Vocalizations of the boreal owl, Aegolius funereus richardsoni, in North America".Canadian Field-Naturalist.98(2): 191–197.doi:10.5962/p.355125.
  17. ^Alaska Department of Fish and Game The Boreal Owl.[1],Retrieved on May 10, 2013.
  18. ^"Boulder County Nature Association".RetrievedMay 10,2013.
  19. ^abcdKorpimäki, Erkki; Hakkarainen, Harri (2012-09-27).The Boreal Owl: Ecology, Behaviour and Conservation of a Forest-Dwelling Predator(1 ed.). Cambridge University Press.doi:10.1017/cbo9780511844164.ISBN978-0-511-84416-4.
  20. ^Löfgren, O.; Hörnfeldt, B.; Carlsson, B. -G. (1986-06-01)."Site tenacity and nomadism in Tengmalm's owl (Aegolius funereus (L.)) in relation to cyclic food production".Oecologia.69(3): 321–326.Bibcode:1986Oecol..69..321L.doi:10.1007/BF00377051.ISSN1432-1939.PMID28311331.
  21. ^Korpimäki, Erkki (1986-05-01)."Gradients in population fluctuations of Tengmalm's owl Aegolius funereus in Europe".Oecologia.69(2): 195–201.Bibcode:1986Oecol..69..195K.doi:10.1007/BF00377621.ISSN1432-1939.PMID28311358.
  22. ^Sonerud, Geir A.; Solheim, Roar; Prestrud, Kristen (1988)."Dispersal of Tengmalm's Owl Aegolius funereus in Relation to Prey Availability and Nesting Success".Ornis Scandinavica (Scandinavian Journal of Ornithology).19(3): 175–181.doi:10.2307/3676555.ISSN0030-5693.JSTOR3676555.
  23. ^Journal of Raptor Research (2024-01-06)."Habitat Selection, Movements and Activity of Boreal and Saw-whet Owls".Journal of Raptor Research.21(1).
  24. ^Korpimaki, E. (1981). On the ecology and biology of Tengmalm's Owl (Aegolius funereus) in southern Ostrobothnia and Suomenselka, western Finland. Acta Univ. Ouluensis A 118 Biol. 13:1-84
  25. ^März, R. (1968). Der Rauhfusskauz. Wittenberg-Lutherstadt: Die Neue Brehm-Bücherei 394.
  26. ^Joneniaux, A. and G. Durand. (1987). Forest management and population ecology of Tengmalm's Owl. Rev. Ecol. Terre et la Vie, Supl. 4:84-87
  27. ^Korpimäki, Erkki; Norrdahl, Kai (1989)."Predation of Tengmalm's Owls: Numerical Responses, Functional Responses and Dampening Impact on Population Fluctuations of Microtines".Oikos.54(2): 154–164.Bibcode:1989Oikos..54..154K.doi:10.2307/3565261.ISSN0030-1299.JSTOR3565261.
  28. ^abc"Aegolius funereus (Boreal owl)".Animal Diversity Web.
  29. ^abc"Boreal Owl | the Peregrine Fund".
  30. ^Norberg, R. A. (1978-03-09)."Skull asymmetry, ear structure and function, and auditory localization in Tengmalm's owl, Aegolius funereus (Linné)".Philosophical Transactions of the Royal Society of London. B, Biological Sciences.282(991): 325–410.Bibcode:1978RSPTB.282..325N.doi:10.1098/rstb.1978.0014.ISSN0080-4622.
  31. ^Holt, Denver W.; Berkley, Regan; Deppe, Caroline; Enríquez, Paula L.; Petersen, Julie L.; Rangel Salazar, José Luis; Segars, Kelley P.; Wood, Kristin L.; Bonan, Arnau (2020-03-04), Del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi; Christie, David; De Juana, Eduardo (eds.),"Buff-fronted Owl (Aegolius harrisii)",Birds of the World,Cornell Lab of Ornithology,doi:10.2173/bow.bufowl1.01,retrieved2024-10-14
  32. ^König, Claus, and Weick (2008).Owls of the world.A&C Black.{{cite book}}:CS1 maint: multiple names: authors list (link)
  33. ^Mikkola, Heimo Juhani (January 1983).Owls of Europe(1st ed.). A.D. & T. Poyser.ISBN0-85661-034-8.{{cite book}}:CS1 maint: date and year (link)
  34. ^Sonerud, G. A. (1985). "Nest Hole Shift in Tengmalm's Owl Aegolius funereus as Defence Against Nest Predation Involving Long-Term Memory in the Predator".The Journal of Animal Ecology.54(1): 179–192.Bibcode:1985JAnEc..54..179S.doi:10.2307/4629.JSTOR4629.S2CID86967254.
  35. ^Herrera, Carlos M.; Hiraldo, Fernando (1976)."Food-Niche and Trophic Relationships among European Owls".Ornis Scandinavica (Scandinavian Journal of Ornithology).7(1): 29–41.doi:10.2307/3676172.ISSN0030-5693.JSTOR3676172.
  36. ^Piorecky, Mark D.; Prescott, David R. C. (2004).Distribution, abundance and habitat selection of northern pygmy and barred owls along the Eastern Slopes of the Alberta Rocky Mountains /.[Edmonton]: Alberta Sustainable Resource Development, Fish & Wildlife Division, Resource Data and Species at Risk Section.doi:10.5962/bhl.title.113788.
  37. ^Korpimäki, Erkki (1992)."Fluctuating Food Abundance Determines the Lifetime Reproductive Success of Male Tengmalm's Owls".Journal of Animal Ecology.61(1): 103–111.Bibcode:1992JAnEc..61..103K.doi:10.2307/5513.ISSN0021-8790.JSTOR5513.
  38. ^Sonerud, Geir A.; Solheim, Roar; Prestrud, Kristen (1988)."Dispersal of Tengmalm's Owl Aegolius funereus in Relation to Prey Availability and Nesting Success".Ornis Scandinavica.19(3): 175.doi:10.2307/3676555.ISSN0030-5693.JSTOR3676555.
  39. ^Korpimäki, Erkki (1986)."Gradients in population fluctuations of Tengmalm's owl Aegolius funereus in Europe".Oecologia.69(2): 195–201.Bibcode:1986Oecol..69..195K.doi:10.1007/bf00377621.ISSN0029-8549.PMID28311358.
  40. ^abCocker, Bruce Marcot, David Johnson, Mark."Owls in Lore and Culture (Page 2 of 3)".The Owl Pages.Retrieved2024-10-15.{{cite web}}:CS1 maint: multiple names: authors list (link)
  41. ^Hussain, Shumon T. (2019-10-02)."Gazing at Owls? Human-strigiform Interfaces and their Role in the Construction of Gravettian Lifeworlds in East-Central Europe".Environmental Archaeology.24(4): 359–376.Bibcode:2019EnvAr..24..359H.doi:10.1080/14614103.2018.1434854.ISSN1461-4103.
  42. ^Ornithology, British Trust for (2019-03-21).A review of raptor and owl monitoring activity across Europe: its implications for capacity building towards pan-European monitoring.

Sources

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  • Cramp, Stanley,ed. (1985). "Aegolius funereusTengmalm's Owl ".Handbook of the Birds of Europe the Middle East and North Africa. The Birds of the Western Palearctic.Vol. IV: Terns to Woodpeckers. Oxford: Oxford University Press. pp. 606–616.ISBN978-0-19-857507-8.
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