Distribution, abundance, and habitat use of singing male Boreal Owls in northeast Minnesota

Citation
Wh. Lane et al., Distribution, abundance, and habitat use of singing male Boreal Owls in northeast Minnesota, J RAPT RES, 35(2), 2001, pp. 130-140
Citations number
50
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Animal Sciences
Journal title
JOURNAL OF RAPTOR RESEARCH
ISSN journal
0892-1016 → ACNP
Volume
35
Issue
2
Year of publication
2001
Pages
130 - 140
Database
ISI
SICI code
0892-1016(200106)35:2<130:DAAHUO>2.0.ZU;2-I
Abstract
Compared to other portions of their breeding range, little is known regardi ng distribution, abundance, and habitat use of Boreal Owls (Aegolius funere us) at the southern extent of the boreal forest in eastern North America. T o locate Boreal Owls and evaluate abundance and habitat use, we conducted n octurnal surveys for singing male owls in northeast Minnesota from 1987-92. Vocalizing owls were detected on 234 occasions in almost 5000 km of survey s, with 172 (73.5%) of the detections categorized as unique (i.e., individu al owls) and 62 (26.5%) detections categorized as owls previously detected (heard during greater than or equal to1 previous survey effort). The rate o f encounter of singing owls ranged from a low of 0.030 owls/km surveyed in 1987 and 1991 to a high of 0.089 owls/km surveyed in 1989. Indices of abund ance based on unique detections ranged from 0.060 owls/km of survey route i n 1987 to 0.219 owls/km of survey route in 1989, and minimum density estima tes ranged from 0.014 (1987) to 0.051 (1989) singing male Boreal Owls per k m(2). No trends in abundance, except an apparent peak in abundance in 1989, were evident across years, although high spatial variation constrained our ability to detect trends. Singing male Boreal Owls used older, upland-mixe d-forest stands greater than expected based on availability along survey ro utes and open/brush/regenerative stands significantly less than expected fo r courtship activities.