Treesearch

We banded 555 Burrowing Owls (Speotyto cunicularia) either as adults (after hatch year; AHY) or as young of the year (hatch year; HY) and used capture-recapture models to estimate survival and recapture rates and Leslie matrix models to project population growth over time at the 6,900-ha Rocky Mountain Arsenal National Wildlife Refuge (RMANWR), Colorado from 1990-1994. W e found survival rates for AHY could be pooled across sexes and that survival varied by year. Survival for AHY birds between 1990-1991 was 0.71 and averaged 0.18 for the period 1991-1994 (P = 0.06). Survival for HY birds...

This study examined the diurnal roosting behavior of male Eastern Screech-owls (Otus asio) and proposed some possible functions for this behavior. As part of a nest defense study, male diurnal roost locations were marked and, later, the distance to the corresponding nest was measured. Male screech-owls roosted significantly closer to their nests during the nestling stage than during the egg stage. Additionally, males associated with nests in natural cavities roosted significantly closer to their nests than did males with nests in nest boxes. Comparison of nest sites showed significantly...

This paper reports on 245 pellet samples containing 479 identified prey items collected at six Northern Spotted Owl (Strix occidentalis caurina) breeding sites in the eastern portion of its range. The majority of prey (biomass) came from four species; northern flying squirrels (Glaucomys sabrinus), bushy-tailed woodrats (Neotoma cinerea), northern pocket gopher (Thomomys talpoides), and pika (Ochotona princes). Flying squirrels were the most important dietary item, similar to the food habits of spotted owls in more mesic forests of Oregon and Washington.

Using a Geographic Information System (GIS), a sensitivity analysis was performed on estimated mapping errors in vegetation type, forest canopy cover percentage, and tree crown size to determine the possible effects error in these data might have on delineating suitable habitat for the California Spotted Owl (Strix occidentalis occidentalis) in southern California. The maps were developed as part of a project to map existing vegetation for the USDA Forest Service in southern California using Landsat Thematic Mapper satellite data, and GIS modeling. The research area is the San Bernardino...

Much like the caged canary used by miners, a plethora of wildlife species have been promoted as biomonitors of environmental contamination. These species provide an "early warning system" for toxic contaminants in the environment. Species promoted as useful biomonitors share many common life history characters, such as wide distribution, territorial, non-migratory behavior, high trophic status, and high reproductive rates.

To determine habitat use and movements of male Boreal Owls (Aegolius funereus) in northeast Minnesota, we monitored 10 radio-equipped owls from 1990-1992. We used mist nets, bal-chartris, and the taped playback recording of the primary song of the male Boreal Owl to trap territorial male owls during the springtime breeding season.

The Burrowing Owl (Speotyto cunicularia) inhabits open prairie grassland habitat in the midwestern and western US and Canada. For several years now, numbers of this species in North America have been declining at an alarming rate. Currently, Burrowing Owls are listed as endangered in Canada and threatened in Mexico. In the United States, the Burrowing Owl was listed as a Candidate 2 species by the USFWS until 1996, but currently is not formally a listed species.

The purpose of the study was to find where and why two species of owls were killed by traffic along motorways. Three different factors have an important influence on the mortality of the two owl species: the biotops crossed by motorways, the road elevation and the presence of small rodents, the Common Vole (Microtus arvalis) being most numerous. In order to limit the mortality caused by motorways, it is proposed to let the bordering vegetation grow naturally.

During autumn migration 1980-1994, 1,270 Northern Saw-whet Owls (Aegolius acadicus) (NSWO) were captured and banded at Cape May Point, NJ. From 1980-1988, captures were effected by passive mist-netting. From 1989-1994, an audiolure (NSWO territorial song broadcast loudly from dusk to dawn in the trapping area) was used to enhance capture rate. 638 NSWOs were captured with an audiolure during five seasons (3.08 owls/100 net-hours), while 632 NSWOs were captured in nine seasons by passive mist-netting (0.51 owls/100 net-hours). Comparisons of age, mass, weather conditions when peak capture...

We conducted nocturnal auditory surveys from 1987-1992 to determine the distribution, abundance, and habitat use of Boreal Owls (Aegolius funereus) in northeast Minnesota. We concentrated our efforts in areas where documented nesting attempts by the owls had occurred, along roadways maintained for winter-time access by motor vehicles, and by traversing all habitat types found within the study area.