Burrowing Owl (Athene cunicularia)
The Burrowing Owl (BUOW) is a small, diurnal owl that typically occupies sparsely vegetated flat areas. BUOW utilize previously constructed animal burrows (e.g. California ground squirrels, coyotes) or man-made structures such as culverts, pipes, or soil piles. Their diet consists of arthropods, amphibians, small rodents, and reptiles.
CA State Species of Special Concern (CDFW)
Suitable BREEDING Habitat
Suitable habitat consists of low-lying and/or sparsely vegetated open areas that have suitable burrows or burrow alternates and a healthy prey base (CDFW 2012).
The breeding season can begin as early as February 1 and goes through August 31, with peak breeding typically occurring from mid-April through mid-July. Eggs are incubated for approximately 29 days and young typically fledge at 44 days of age. After successful fledgling, the adult BUOW may relocate young to a nearby burrow in order to decrease predation risk--doing this multiple times before the young are fully independent (CDFW 2012).
BUOW continue to utilize burrows during the non-breeding season, called wintering sites, that play a crucial role in the species survival.
Habitat assessments are necessary in order to determine the suitability of the habitat to support BUOW. The entire proposed impact area as well as a 150 m buffer, where suitable habitat exists, should be surveyed prior to conducting the survey round. The purpose of the visit is to document the habitat vegetation, topography, potential burrow sites, BUOW sign (i.e. scat, pellets, whitewash), BUOW individuals, and to determine the probability of the habitat supporting BUOW.
In order to determine the presence of BUOW during the breeding season, four visits must be conducted in total. The first visit must occur between February 15 through April 15. The remaining three visits, spaced at least three weeks apart from one another, need to occur between April 15 through July 15--with at least one visit after June 15. Non-breeding season surveys may be conducted between September 1 and January 31 where at least four, evenly spread, site visits are conducted. It should be noted, that in the event negative survey results are observed, that does not always directly translate to site unsuitability or absence.
(DFG) California Department of Fish and Wildlife. 2012. Staff Report on Burrowing Owl Mitigation. Sacramento, CA, USA.