Glaucidium gnoma

Life-forms

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Megaclassis: Osteichthyes
Cladus: Sarcopterygii
Cladus: Rhipidistia
Cladus: Tetrapodomorpha
Cladus: Eotetrapodiformes
Cladus: Elpistostegalia
Superclassis: Tetrapoda
Cladus: Reptiliomorpha
Cladus: Amniota
Classis: Reptilia
Cladus: Eureptilia
Cladus: Romeriida
Subclassis: Diapsida
Cladus: Sauria
Infraclassis: Archosauromorpha
Cladus: Crurotarsi
Divisio: Archosauria
Cladus: Avemetatarsalia
Cladus: Ornithodira
Subtaxon: Dinosauromorpha
Cladus: Dinosauriformes
Cladus: Dracohors
Cladus: Dinosauria
Ordo: Saurischia
Cladus: Eusaurischia
Subordo: Theropoda
Cladus: Neotheropoda
Cladus: Averostra
Cladus: Tetanurae
Cladus: Avetheropoda
Cladus: Coelurosauria
Cladus: Tyrannoraptora
Cladus: Maniraptoromorpha
Cladus: Maniraptoriformes
Cladus: Maniraptora
Cladus: Pennaraptora
Cladus: Paraves
Cladus: Eumaniraptora
Cladus: Avialae
Infraclassis: Aves
Cladus: Euavialae
Cladus: Avebrevicauda
Cladus: Pygostylia
Cladus: Ornithothoraces
Cladus: Ornithuromorpha
Cladus: Carinatae
Parvclassis: Neornithes
Cohors: Neognathae
Cladus: Neoaves
Ordo: Strigiformes

Familia: Strigidae
Subfamilia: Surniinae
Genus: Glaucidium
Species: Glaucidium gnoma
Name

Glaucidium gnoma Wagler, 1832
References

Wagler, J.G. 1832. Mittheilungen über einige merkwürdige Thiere. Isis von Oken 25: 275–282. BHL (German) Reference page. col. 275 BHL

Links

IUCN: Glaucidium gnoma (Least Concern)

Vernacular names
العربية: بوم أقزم شمالي
català: Mussolet muntanyenc
čeština: Kulíšek americký
Cymraeg: Cordylluan y Gogledd
English: Northern Pygmy-Owl, Mountain Pygmy-Owl
español: Mochuelo chico
suomi: Lännenvarpuspöllö
français: Chevêchette naine
Nederlands: Bergdwerguil
norsk: Gnomugle
Diné bizaad: Dziłtah biniiʼdootłʼizh
polski: sóweczka dwuplamista
português: Coruja-anã
русский: Воробьиный сыч-гном
shqip: Huti i maleve
svenska: Mexikansk sparvuggla

The mountain pygmy owl (Glaucidium gnoma) is a small species of owl from the family Strigidae. They reside throughout southern Arizona, New Mexico and Mexico.

There is current taxonomic debate regarding its classification as an independent species or subspecies from that of the northern pygmy owl. Similar plumage colour and different vocal patterns are the primary characteristics fuelling this confusion.

The mountain pygmy owl hunts for small mammals and insects during the day from its high perches in pine-forested mountains, at elevations of 1,500 to 3,500 m. Breeding occurs once the female has chosen the appropriate cavity to form her nest. The female mountain pygmy owl will lay eggs between May and June. Owlets will leave their nests 23-30 days, after hatching. Although the International Union for Conservation of Nature (IUCN), has ranked this species as least-concerned, the increase in deforestation could impact the future population.

Taxonomy

The taxonomy of the pygmy owl genus (Glaucidium), remains disputed amongst taxonomic authorities. The International Ornithologists' Union, considers the Mountain pygmy owl (Glaucidium gnoma) to be a separate species from the Northern pygmy owl (Glaucidium californicum).[3] Whereas, the American Ornithological Society has amalgamated the Mountain, Guatemalan (Glaucidium cobanense), Cape (Glaucidium hoskinsi) and Northern pygmy owl, as the same species (conspecific) and classifies them all under Glaucidium gnoma and further categorizes them into respective subspecies.[4] This northern pygmy owl complex ranges from North America to Central America.[4] However, individuals inhabiting these regions, demonstrate unique vocal patterns, indicating distinct species and population distribution.[4] Although more research is required, genetic sequencing based on cytochrome b and nuclear markers, suggests that Glaucidium gnoma and Glaucidium californicum are not conspecific.[4][5]
Description

The adult mountain pygmy owl is approximately 15–17 cm (5.9–6.7 in) in length.[5] Males weigh between 48–54 g (1.7–1.9 oz); however, reverse sexual dimorphism indicates that adult females are larger in mass reaching between 60–73 g (2.1–2.6 oz).[5] The wing length of a male is 86–89 mm (3.4–3.5 in) and a female is 87–98 mm (3.4–3.8 in) while the tail of both sexes can reach 61–66 mm (2.1–2.6 in).[5][6]

Adult plumage colour is similar to that of most pygmy owls. The chest and throat are white, while the face is a deeper brown.[7] The colour of the facial disk is a pale brownish-red (rufous), containing flecks of cream. In addition, their eyebrows are thin in shape and white in colour.[7] The head, neck, wings and tail have a pale rufous base colour, with a cream spotted pattern. The exterior of the tail has 5 to 6 alternating bands of white and rufous.[7] Whereas, visible on the underside of the tail are 3 to 4 alternating bars.[7] The chest and underside are white with vertical, broken streaks of red-brown. The iris colour is yellow, similar to the colour of the feet and bill.[7]

The plumage of nestlings (chicks) consists of whiteish natal down feathers.[5] Within a few weeks, their second layer of down feathers start to appear. The fledgling (juvenile) plumage resembles that of the adult pygmy owl.[5] However, the crown (top of head) is grey, with minimal spotting on the forehead. Moreover, the eyebrows are white, thicker and more prominent than that of the adult.[5]
Visual identification

The individuals within the northern pygmy owl complex, although similar, each have their own characteristics used for identification. The mountain pygmy owl is small, with a short tail and slightly pointed wing-tips.[8] In comparison to the northern pygmy owl, which is larger in stature with rounded wing-tips and a longer tail.[8] The guatemalan pygmy owl is distinguished by its vibrant red-brown plumage and white centre tail bars surrounded by a dark trim.[8] The cape pygmy owl is also small in size, similar to the mountain pygmy owl, however has rounded wing-tips like that of the northern pygmy owl. In addition, its throat is white in colour.[8]
Habitat and Distribution

The mountain pygmy owl resides in tropical and subtropical forests of Oak, Pine and Evergreens; located in mountainous terrain at elevations from 1,500 to 3,500 m.[5] Although, forests primarily composed of Ponderosa pines are preferential, as the reduced forest understory facilitates their hunting behaviours.[8]

The species is distributed from southern Arizona and New Mexico to Oaxaca, part of the southern tip of Mexico.[5]
Behaviour

Individuals within the northern pygmy owl complex demonstrate similar behaviours, they are known to be aggressive, and relatively unsocial when compared to other owl species.[7][8] They prefer to live alone, when not engaging in breeding pairs.[8]
Vocalization

There is limited information regarding specific seasonal calls or songs, pertaining to the mountain pygmy owl. However, it is suggested that vocal behaviour observed in the Eurasian pygmy owl (Glaucidium passerinum), can be applied to the other pygmy owl species.[8] Pygmy owls in British Columbia to California have a slow single hoot, compared to pygmy owls in southern British Columbia which have a slow double hoot. Whereas, individuals in the interior United States to Arizona have a fast single hoot, and a fast double hoot can be heard from Southern Arizona to Southern Mexico.[7] Calls consist of two categories, primary and secondary. Territorial calls are considered primary and consist of an echoed single and or double "hooting/tooting", which can be heard close to sunrise and after sunset throughout the year. These calls can be heard more frequently in spring and fall.[8] In addition, during nesting season, the male will call ahead with a soft hoot, when approaching the nesting cavity with food. The female has a similar but broken call, which she uses in communication with the male and when in danger.[8] A form of duetting can be heard, where the male will hoot first and the female will answer in a lower tone. The secondary call is a song of increasing pitch that consists of 11 hoots.[8] This call can be heard by both males and females, throughout the year. Furthermore, it is more frequent during autumn, when protecting their territory and encouraging their young to leave the nest.[8]
Diet and Hunting

The diet of the mountain pygmy owl consists of the following: insects, orthopterans (crickets, grasshopper), beetles, small mammals (rodents) and reptiles.[5] Their diet consists of a large portion of songbirds including the American robins and larger species.[9][7]

Pygmy owls have a rather unique feeding habit, as they can consecutively consume prey head first.[8] However, when consuming snakes, they do so tail first. They have a very high metabolism and require a constant food supply.[8] The pygmy owl's lack of a crop and inefficient gastric digestion, inhibits its ability to digest bones, thus causing the formation and regurgitation of pellets.[8]

The pygmy owl is a diurnal hunter but is also known to hunt around dawn and dusk.[8] Interestingly, when in flight, the wings of the pygmy owl make noise, unlike other owl species which are silent fliers.[8] While perching on a high branch it will search for prey, once found, the pygmy owl will dive to the ground to catch it. It is significant to note that, if the attempt fails the owl will immediately search for new hunting grown's.[8] The reason for this behaviour is that the pygmy owl is commonly mobbed by songbirds.[5][8] This is a form of defence, where multiple songbirds will swarm a predator forcing them to leave the area.
Movement

This species is mainly residential, as they do not migrate.[10] The further northern pygmy species have a limited winter migration, descending from mountain regions to closer lowlands.[8]
Reproduction

Little has been observed regarding the social behaviour and reproduction of the mountain pygmy owl, data available is from the Eurasian pygmy owl, but can be generalized and applied to the Northern pygmy complex.[8] Sexual maturity can commence at 5 months of age, followed by breeding at the age of 1 year.[8] Pygmy owls form monogamous pairs, usually span one breeding season. Though, a pairing could return to the same nesting location for up to four years.[8] The male displays courtship behaviour by a series of consistent hoots while jumping from branch to branch within a claimed territory. Initially, both sexes demonstrate hesitation and aggression towards each other.[8] Duet singing decreases when the male demonstrates nesting behaviour.[8] Nests are formed in either hollowed tree cavities or woodpecker holes.[5] Once the male locates a possible nest, he will fly into it and inform the female via his call so that she may inspect it. The female will choose the ideal cavity and begin to clean it; copulation will occur soon after.[8]

Mountain pygmy owls lay eggs between May 19 to June 14.[8] Clutches range between 2 to 4 white eggs, which are laid at the base of the nest.[5] The female will commence the approximate 28 day incubation period, once all the eggs have been laid. This would explain why chicks hatch within a short period of each other.[8] It is thought that the mountain pygmy owl demonstrates similar feeding behaviour to that of the Eurasian pygmy owl. Once the eggs have hatched, the male mountain pygmy owl will provide more food to the female.[8] An estimated 14 days after hatching, nestlings have attained approximately 60% of their mature weight.[8] It has been observed in several pygmy owl species that, within a month of hatching, 23-30 days, juveniles are able to fly and will leave their nests.[8] The parental pair will remain in the vicinity of the nest, and provided protection for upwards of 20-30 additional days.[8]
Grooming

The practice of preening (grooming) is demonstrated across all owl species. They clean their feathers and remove foreign debris by carefully passing the feather through their partially open bill.[8] Waterproofing of feathers is obtained by using their beak to spread the oil from their uropygial gland. This gland is located on the outer-side of the body, at the start of the tail.[8] Facial feathers are maintained by the owl using its talons. Within breeding pairs allopreening, (both owls clean each other) has also been observed in owls of the northern pygmy complex.[8]
Conservation

According to the International Union for Conservation of Nature (IUCN) the mountain pygmy owl is categorized as a least-concern species.[11] However, the species is suspected to be declining in population due to habitat loss, from deforestation and fragmentation.[5][11]
References

BirdLife International (2016). "Glaucidium gnoma". The IUCN Red List of Threatened Species. IUCN. 2016: e.T61791135A95180896. doi:10.2305/IUCN.UK.2016-3.RLTS.T61791135A95180896.en. Retrieved 15 January 2018.
"Appendices | CITES". cites.org. Retrieved 2022-01-14.
"BOW (Birds of the World) – IOC World Bird List". Retrieved 2021-11-12.
Eisermann, Knut; Howell, Steve N. G. (2011). "Vocalizations of the Guatemalan Pygmy-Owl (Glaucidium cobanense)". Journal of Raptor Research. 45 (4): 304–314. doi:10.3356/JRR-10-73.1. ISSN 0892-1016.
König, Klaus (2008). Owls of the world. Friedhelm Weick, Michael Wink (2nd ed.). London: Christopher Helm. pp. 43, 50, 162, 397, 398. ISBN 978-1-4081-3578-5. OCLC 769189719.
Deshler, John F. (2021-04-28). "Higher reversed sexual size dimorphism among nesting pairs of Northern Pygmy-Owls (Glaucidium gnoma) in northwestern Oregon than among specimens collected at the range-wide scale". The Wilson Journal of Ornithology. 132 (3). doi:10.1676/19-132. ISSN 1559-4491.
Howell, Steve N. G. (1995). A guide to the birds of Mexico and northern Central America. Sophie Webb. Oxford: Oxford University Press. pp. 360, 361. ISBN 0-19-854013-2. OCLC 28799888.
Johnsgard, Paul A. (2002). North American owls : biology and natural history (2nd ed.). Washington, D.C.: Smithsonian Institution Press. pp. 33, 35, 139, 140, 142, 141, 143, 144. ISBN 1-56098-939-4. OCLC 48943959.
Hayward, G. D.; Garton, E. O. (1988). "Resource partitioning among forest owls in the River of No Return Wilderness, Idaho". Oecologia. 75 (2): 253–265. doi:10.1007/BF00378606. ISSN 0029-8549.
König, Claus (1999). Owls : a guide to the owls of the world. Friedhelm Weick, J. H. Becking. New Haven: Yale University Press. p. 356. ISBN 0-300-07920-6. OCLC 42890802.
International), BirdLife International (BirdLife (2016-10-01). "IUCN Red List of Threatened Species: Glaucidium gnoma". IUCN Red List of Threatened Species. doi:10.2305/iucn.uk.2016-3.rlts.t61791135a95180896.en.