NORTHERN PYGMY-OWL

Glaucidium gnoma

Northern Pygmy-Owl is an aggressive diurnal predator, often catching prey twice its weight (57-66g [2-2.3 oz]. Holt and Petersen 2000). Individuals may also  be curious, attracted by an imitation of the call of another small owl (RCT).


This owl is a complex of 3 or more possible species: the californicum group in the United States and Canada, the gnoma group of mainland Mexico, Guatemala and central Honduras and the hoskinsii group of  southern Baja California (Am, Ornithol. Union 1998). The ranges of the first two groups do not split neatly at the United States-Mexico border, both californicum (rare) and gnoma (uncommon) are present in southern Arizona (Rosenberg and Stejskal 1999). Howell and Webb (1995) suggest californicum consists of two populations, a Pacific Coast race which gives single hoots with a slow cadence and an interior race which hoots singly at a faster rate. The gnoma group gives double hoots at a fast pace. Colvin (1999) provides recordings of these three calls. 

The group present in Trans-Pecos Texas is the subject of disagreement, the AOU Checklist (Am. Ornithol. Union 1998) says californicum is casual in west Texas, while the TOS Handbook reports gnoma is accidental (Lockhart and Freeman 2004). Probably both forms have been present. 

DISTRIBUTION. During the 1987-1992 field work for the  TBBA project, volunteers found 2 possible breeding records in latilong block 31104 (Guadalupe Mountains) and 1 possible record in 30104 (Davis Mountains). Lockwood and Freeman (2004) report documented records from the Chisos Mountains as well.

The range of Northern Pygmy-Owl extends from southeast Alaska through the mountains of the western United States and Canada and the higher elevations of Mexico and Guatemala to the Honduran border (Holt and Petersen 2000).


SEASONAL OCCURRENCE. Lockwood and Freeman (2004) report 2 documented records in April and August, respectively. Within its breeding range this owl is a year-round resident near its breeding site, sometimes moving to lower elevations in winter (Holt and Petersen 2000. In Arizona territories are established in February and March with pairs seen in late March and nests with eggs 

 

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from April 26 to June 12. Fledglings were seen from June 5 to late July (Corman 2005). In Colorado fledglings were found from May 15 to August 30 (Jones 1998). 

BREEDING HABITAT. Northern Pygmy- Owls are cavity nesters, using old woodpecker holes or natural cavities in trees. In Arizona about 59% of atlas records came from tall pine and pine-oak forests. In southeast Arizona breeding was also found in evergreen oaks, and riparian vegetation (Corman 2005). These records may represent breeders of the gnoma

group. In Colorado 70% of breeding was found in coniferous forests and the remainder in aspen and deciduous riparian habitats (Jones 1998). In Mexico this species breeds in pine and pine-oak habitats (Howell and Webb 1995).


Nest cavities are difficult to locate, so information is sketchy. Feathers, leaves and other materials are apparently used as a lining. The size of the cavity probably depends on the tree species and the woodpecker species which created it. Reuse of cavities in successive years has been observed. 

A female usually lays 4-5 (range 2-7) glossy, white eggs. She is estimated to incubate the eggs for 28 days while her mate brings her prey. The young birds all leave the nest about the same time (about 23 days old) even though they may have hatched on different days (Holt and Petersen 2000).         

STATUS. Lockwood and Freeman (2004) describe this owl as accidental in the mountains of the Trans-Pecos. The North American Breeding Bird Survey does not sample this owl in Texas but data from 62 routes across the species' range in the United States and Canada provide a 95% confidence interval (There is a 95% chance that the actual population trend will be between these two numbers.) of -2.1 to +3.1% population change per year for the period 1966-2004 (Sauer et al. 2005). This confidence interval suggests the population of Northern Pygmy-Owl is stable across its range (north of Mexico).

Text by Robert C. Tweit (2006).
Map 
Literature cited.
American Ornithologist' Union. 1998. Checklist of North American birds. Am. Ornithol. Union, Washington, DC.

Colvin, K. J. 1999. Stokes field guide to bird songs, western region. Time Warner Audio Books.

Corman, T. E. 2005. Northern Pygmy-Owl (Glaucidium gnoma). In Arizona breeding bird atlas. pp. 206-207 (T. E. Corman and C. Wise-Gervais, eds.), University of New Mexico Press, Albuquerque.

Holt, D.W. and J. L. Petersen. 2000. Northern Pygmy-Owl (Glaucidium gnoma). In The birds of North America, No. 494 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.

Howell, S. N. G. and S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, New York.

Jones, S. R. 1998. Northern Pygmy-Owl (Glaucidium gnoma). In Colorado breeding bird atlas, pp. 218-219 (H. E. Kingery, ed.), Colorado Bird Atlas Partnership, Denver.

Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M Univ. Press, College Station.

Rosenberg, G. H. and D. Stejskal. 1999. Annotated checklist and seasonal bar graphs. In Davis and Russell's finding birds in southeast Arizona. Tucson Audubon Soc., Tucson..

Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, results and analysis 1966-2004. Version 2005.1. USGS Patuxent Wildlife Research Center, Laurel MD (Web site, http://www.mbr-pwrc.usgs.gov/bbs).