Glaucidium gnomamountain pygmy-owl(Also: northern pygmy owl)

Ge­o­graphic Range

There has been much de­bate over the clas­si­fi­ca­tion of Glau­cid­ium gnoma cal­i­for­nicum. Some ex­perts now be­lieve that these G. gnoma cal­i­for­nicum de­serves spe­cific sta­tus as G. cal­i­for­nicum, but the tax­on­omy of the genus Glau­cid­ium is con­tro­ver­sial. Ev­i­dence used in sup­port of their spe­cific sta­tus in­clude their vo­cal­iza­tions. Be­cause owls in gen­eral are pri­mar­ily noc­tur­nal, or ac­tive at dusk and night, their phys­i­cal ap­pear­ance and plumage pat­terns are be­lieved to be less im­por­tant than their calls and songs (Hei­drich et al. 1995). Glau­cid­ium gnoma cal­i­for­nicum, un­like other G. gnoma pop­u­la­tions, pri­mar­ily hunt dur­ing the day. Glau­cid­ium gnoma re­sides on the west coast of North Amer­ica (ex­tend­ing from Canada, down to Cen­tral Amer­ica) (Holt 2000), Glau­cid­ium gnoma cal­i­for­nicum in­hab­its a more com­pact re­gion on the west coast, through the Rocky Moun­tains - from south­ern Alaska to south­ern Cal­i­for­nia (Owl Pages 2000).

Habi­tat

These owls in­habit open conif­er­ous and mixed forests, but are not found in dense, con­tin­u­ous forests. This may have to do with the use of open spaces and clear­ings where they dive down at their prey. They also hunt in open fields, wet­lands, logged areas, and the edge of mead­ows (Owl Pages 2000). Be­cause they rely so heav­ily on old wood­pecker cav­i­ties for their nests, this se­lec­tion of habi­ta­tion may not be solely due to their pref­er­ences, but focus around where these wood­peck­ers re­side as well.

Glau­cid­ium cal­i­for­nicum prefers to roost in quiet, shady alder thick­ets (Owl Pages 2000). (The Owl Pages, 2000)

Phys­i­cal De­scrip­tion

The North­ern Pygmy Owl's most dis­tin­guish­ing fea­ture is its "extra pair of eyes" found on the back of its head. These two black teardrop-shape mark­ings, bor­dered by white, re­sem­ble eyes. The rest of this owl's head is, de­pend­ing on its habi­ta­tion, gray, red, or brown in color - cov­ered on the sur­face by small white dots. Glau­cid­ium cal­i­for­nicum's light belly is ac­cented by thick brown stripes run­ning ver­ti­cally down its chest (Owl Pages 2000).

The males and fe­males are fairly sim­i­lar in ap­pear­ance. Their av­er­age wingspan is 38 cm. The fe­male's av­er­age length, how­ever, is slightly larger: 18.5 cm, com­pared to 16.5 cm in males. Though very small in size, the North­ern Pygmy Owl's tail, which when sit­ting is held slightly cocked up­wards, is com­par­a­tively long and is striped six or seven times by light-white stripes (Owl Pages 2000). Both male and fe­male have large yel­low eyes, a yel­low horn­bill, and gray­ish yel­low-feath­ered legs and toes.

Though the North­ern Pygmy Owl's plumage doesn't show any sea­sonal vari­a­tion, their coat col­ors from the north to down south demon­strates con­sid­er­able dif­fer­ences. In the north­ern re­gions, this bird's upper parts are much grayer than in the south where the bird's feath­ers are browner (Holt 2000). The ju­ve­niles are sim­i­lar in color to their par­ents, but with fluffier unspot­ted plumage, and grayer heads (Owl Pages 2000).

Re­pro­duc­tion

Glau­cid­ium cal­i­for­nicum breed from April to early June (Birds 2000). Though it is not known which sex is re­spon­si­ble for pick­ing and build­ing the nest, the ac­tual sites are al­most al­ways old wood­pecker cav­i­ties. The trees in which these birds nest are usu­ally conif­er­ous, and are found within bo­real and de­cid­u­ous forests. Glau­cid­ium cal­i­for­nicum have clutch sizes that range from 3 to 7, which the fe­male in­cu­bates for about 29 days while the male is re­spon­si­ble for bring­ing back food to the nest. He also de­fends it from any preda­tors. After the fledg­lings hatch, they grow quickly and reach al­most adult size after 2 weeks. They fledge at ap­prox­i­mately 30 days, but are de­fended and cared for by their par­ents for an extra 20 to 30 days (Owl Pages 2000).

Be­hav­ior

Glau­cid­ium cal­i­for­nicum is soli­tary (Holt et al. 1990). Very ter­ri­to­r­ial, these owls -- es­pe­cially the fe­males -- fight by lock­ing feet in the air, and falling to the ground (Holt 2000). This is very dif­fer­ent from courtship, how­ever, where these owls bring food to each other, and have been noted to snug­gle to­gether as well (Owl Pages 2000). Courtship again shows how im­por­tant vo­cal­iza­tions are for owls. The North­ern Pygmy Owl toot and trill in re­sponse to each other from nearby trees. The male then flies to the other, mounts, and cop­u­lates (Holt 2000). Mainly males use calls to de­fend ter­ri­to­ries, and are whis­tled hoots that sound like "too-too-too-too-too-too-too" at in­ter­vals of one or two sec­onds (Owl Pages 2000).

The North­ern Pygmy Owl sleeps with its eyes open -- or so it ap­pears. Ac­tu­ally, after set­tling onto a branch, these birds' clear-white eye­lid (nic­ti­tat­ing mem­brane) cov­ers the eyes. This gives the ap­pear­ance that it's still alert and watch­ing, pos­si­bly to ward off po­ten­tial preda­tors or threats (Holt 2000). When awake, these birds erect their tuft feath­ers as a pos­si­ble mode of con­ceal­ment from prey and preda­tors. These raised ex­ten­sions of the eye­brows re­sem­ble twigs, and are ac­com­pa­nied by an elon­ga­tion of their bod­ies, and press­ing of their feath­ers against their bod­ies (Holt et al. 1990).

Com­mu­ni­ca­tion and Per­cep­tion

Food Habits

Un­like most owls that are ac­tive at night (Hei­drich 1995) and rely mainly on sound or black-and-white vi­sion, Glau­cid­ium cal­i­for­nicum hunts mainly by day. There­fore this bird re­lies mainly on its vi­sion to cap­ture its prey (Owl Pages 2000). An­other no­table dif­fer­ence be­tween this owl com­pared to other owls is its noisy flight. Many owls have spe­cially adapted feath­ers and wings for quiet flight. The North­ern Pygmy Owl's wings not only make noise, but also whis­tle as it soars through the air (Holt 2000).

The North­ern Pygmy Owl is a pre­dom­i­nantly "sit and wait" type of preda­tor. It sits and watches pre­dom­i­nantly from the high­est branches on trees (Owl Pages 2000) mainly for other birds, such as swal­lows, jays and chick­adees, or some­times mam­mals, such as shrews, moles and chip­munks (Holt 2000). When at­tack­ing its prey, it ei­ther dives down to­ward prey on the ground, or jump in a zigzag fash­ion from branch to branch be­fore drop­ping onto its prey with its sharp claws (Holt 2000). These small owls, how­ever, are much more vi­cious than they ap­pear. They at­tack prey or run off preda­tors that are up to sev­eral times their own size (Owl Pages 2000). After they catch a bird, they are plucked and ei­ther eaten en­tirely or only the brains are picked out (Owl Pages 2000).

Con­ser­va­tion Sta­tus

Glau­cid­ium cal­i­for­nicum is cur­rently not en­dan­gered or tar­geted by shoot­ing and trap­ping. As with most for­est-dwelling species, they are sus­cep­ti­ble to habi­tat loss due to log­ging and burn­ing of forests.

Con­trib­u­tors

Gayle Soskolne (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Terry Root (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

visual

uses sight to communicate

Ref­er­ences

Hei­drich, P., C. Koenig, M. Wink. 1995. Bioa­coustics, tax­on­omy and mol­e­c­u­lar sys­tem­at­ics in Amer­i­can Pygmy Owls. Stuttgarter Beitraege zur Naturkunde Serie a (Bi­olo­gie)., 534: 1-47.

Holt, D., R. Kline, L. Sul­li­van-Holt. 1990. A de­scrip­tion of tufts and con­ceal­ing pos­ture in North­ern Pygmy-Owls. J. Rap­tor Res., 24(3): 59-63.

Holt, D., J. Pe­ter­son. 2000. North­ern Pygmy-Owl. Birds of North Amer­ica, 494.

The Owl Pages, 2000. "North­ern Pygmy Owl" (On-line). Ac­cessed Sept 14, 2000 at http://​owlpages.​com/​species/​glaucidium/​californicum/​.