Unspotted Saw-whet Owl
- Order: Strigiformes
- Family: Strigidae
- Polytypic 3 Subspecies
Little information. Unspotted Saw-whet Owl is a predator, probably of small vertebrates such as rodents and shrew (Soricidae), but possibly also birds and bats (Stiles and Skutch 1989).
Little information. Nocturnal. The flight is "fluttery, agile, with quick wingbeats" (Stiles and Skutch 1989).
Little quantitative information. Unspotted Saw-whet Owl responds readily to playback, suggesting that it is very territorial. Otherwise very little is known about its movements (Holt et al. 1999, König and Weick 2008).
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Social and interspecific behavior
Usually solitary. It is possible that Unspotted Saw-whet Owl occurs in pairs only when breeding, as is the case with Northern Saw-whet Owl (Aegolius acadicus) (Holt et al. 1999).
Predation has been considered of high impact in owl communities. Owls could be exposed to predators along gaps or forest borders when are roosting. There is no information specific to predation on Unspotted Saw-whet Owl, however. This species coexists with other owl montane species such as Bearded Screech-Owl (Megascops barbarus), Whiskered Screech-Owl (Megascops trichopsis), Northern Pygmy-Owl (Glaucidium gnoma), and Mottled Owl (Ciccaba virgata). Studies are needed to focus on inter- and intraspecific relationships of Unspotted Saw-whet Owl.
There is very little information about the breeding biology of Unspotted Saw-whet Owl. The breeding season begins in March or April; juveniles can be found in July. An individual collected in April showed gonads lightly development (Moore 1947) and a female captured 20 July 20 1998 had brood patch development (P.L. Enríquez, personal observations). Owls not build nests, but instead use cavities or natural holes and old nest of woodpeckers. As Unspotted Saw-whet Owl is a tropical species, which typically have smaller clutches than related species at northern latitudes, it is possible that it may lay as few as 2 eggs; König and Weick (2008), however, report that the clutch is 5-6, and that the eggs are white.
Populations and Demography
There is no information related to topics such as age at first breeding, life span and survivorship, dispersal, or population regulation for Unspotted Saw-whet Owl.
The relative abundance was estimated in Huitepec Biological Reserv, for the period from January-June 2004, at 0.074 ± 0.001 individuals/km. During a six month study at this site, using recordings of calls to estimate relative abundance, calls were detected only during the first three months of the year (January- March), with March showing the higher detections of the species (0.222 individuals/km) (Martínez-Ortega 2010). This ssuggest that a seasonal pattern to singing in this species, given that no vocalizations were detected during the rest of the study (April-June).
Enríquez, Paula L., M.C. Arizmendi, C. Rodríguez-Flores, and C. Soberanes-González. 2012. Unspotted Saw-whet Owl (Aegolius ridgwayi), 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=%0A%09%09%09%09215576