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Glaucidium costaricanum

Costa Rican Pygmy-Owl

  • Order: Strigiformes
  • Family: Strigidae
  • Monotypic

Authors: Schulenberg, Thomas S

Identification

Summary

Pygmy-owls (Glaucidium) are very small owls, with a large rounded head and a pair of prominent black marks (false "eye spots") on the nape. Costa Rican Pygmy-Owl is a small species of Glaucidium. This species is polymorphic, with a brown and a rufous morph. In both morphs the crown is finely spotted with small pale dots. The brown morph is dark brown above, with small white spots on the brown, and the scapulars and wings coverts also are spotted with white. The breast is mottled brown and white; the lower underparts are white with brown flanks. The rufous morph is less patterned; the upperparts are rufous, the dots on the crown are fewer and are buffy (and so are less contrasting), spots on the scapulars and wing coverts are reduced or absent, and the breast is rufous.

Similar Species

Costa Rican Pygmy-Owl overlaps geographically with two other species of pygmy-owl, Ferruginous Pygmy-Owl (Glaucidium brasilianum) and Central American Pygmy-Owl (Glaucidium griseiceps), but Costa Rican Pygmy-Owl occurs at higher elevations than both of these species. Ferruginous Pygmy-Owl also is larger than Costa Rican, and the crown of Ferruginous is streaked, not spotted. Central American Pygmy-Owl is smaller, shorter tailed, is less strongly above and is more strongly streaked below.

Vocalizations

The song of Costa Rican Pygmy-Owl is described as "a long series of clear, unmodulated toots in an irregular rhythm; often notes seem to come in 2s, sometimes 3 pairs of toots only; occasionally a series of evenly spaced toots" (Stiles and Skutch 1989). In excitement, may give "5 higher-pitched toots in very quick succession" (Stiles and Skutch 1989).

 Additional audio recordings of vocalizations of Costa Rican Pygmy-Owl can be heard at Macaulay Library and at xeno-canto.

Nonvocal Sounds

None reported.

Detailed Description (appearance)

The following description is based on Wetmore (1968):

Adult: Sexes similar. Brown morph: Upperparts brown, blacker at the ends of the primaries and the rectrices. Feathers of forecrown with partly concealed white bases. Crown with irregular white dots, these dots very narrowly bordered with black. Narrow white supercilium. Facial disk dull brown, feathers narrowly barred with buff, basally white. Nape with typical Glaucidium "false eyes" pattern of two large blackish spots, outlined with a narrow pale border. Back brown, more or less spotted, and wings barred, with white and buff. Rectrices with narrow white tip, and crossed by 4 broken white bars (a 5th bar is at the base of the tail, concealed by the uppertail coverts). Throat and center of breast and belly white. Flanks bright brown, narrowly and indistinctly barred with buff and black. 

Rufous morph: Rufous brown both on upperparts and on underparts; pale markings are rufous buff, not white, and are less distinct than in the brown morph.

Bare Parts

Iris: bright yellow

Bill: maxilla light greenish yellow, with yellow tip line along tomia; mandible light dull brown with dull yellow tip; cere dull yellow

Tarsi and toes: bright yellow

Bare parts color data from Wetmore (1968).

Measurements

Total length: 14.5-17 cm (Wetmore 1968), 15 cm (Stiles and Skutch 1989)

Linear measurements (from Wetmore 1968):

male (n = 4):

wing length, mean 91.2 mm (range 88.1-93.9 mm)

tail length, mean 56.1 mm (range 49.5-62.5 mm)

culmen from cere, mean 11.0 mm (range 10.7-11.8 mm)

tarsus, mean 20.5 mm (range 18.8-22.0 mm)

female (n = 1): 

wing length 97.1 mm

tail length 55.1 mm

culmen from cere 11.0 mm

tarsus 20.0 mm

Mass: male, 53-70 g (n = ?; König and Weick 2008), female 99 g (n = 1; König and Weick 2008); 65 g (Stiles and Skutch 1989)

Molts

No information available - Contribute

Geographic Variation

Monotypic.

Systematics

Described as Glaucidium jardinii costaricanum by Kelso (1937), with type locality of "Costa Rica". This taxon was classified as a subspecies of Glaucidium jardinii (Andean Pygmy-Owl) by most authors (e.g. Kelso 1937, Peters 1940, Meyer de Schauensee 1966), although Heidrich et al. (1995) and König et al. (1999) treated it as a subspecies of Northern Pygmy-Owl (Glaucidium gnoma). Robbins and Stiles (1999) concurred that the affiinities of costaricanum are with gnoma, but elevated costaricanum to species rank.

Recommended Citation

Schulenberg, Thomas S. 2012. Costa Rican Pygmy-Owl (Glaucidium costaricanum), Neotropical Birds Online (T. S. Schulenberg, Editor). Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Online: http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=210456