Burrowing Owls (Athene cunicularia) were studied to determine their nesting success and patterns ofnest-site selection in northcentral Oregon during the breeding seasons of 1980 and 1981. Nest success was 57% for 63 nests in 1980 and 50% for 76 nests in 1981. Desertion was the major cause (32%) of nest failures and was related to the proximity of other nesting pairs. Depredation of nests by badgers (Taxidea tams) was the next most frequent cause (14%) of nest failure. Nests lined with livestock dung were significantly less prone to predation than unlined nests. Burrowing Owls occupied three of the five habitats surveyed for pairs. Burrows with good horizontal visibility and little grass coverage were preferred. Elevated perches were used in habitats with average vegetation height > 5 cm and not in habitats with vegetation < 5 cm. Elevated perches presumably improved the Burrowing Owl' s ability to detect both predators and prey by increasing their horizontal visibility. Low grass cover may be indicative of a high availability of prey preferred by Burrowing Owls. The nesting ecology of Columbia Basin Burrowing Owls appears to be strongly influenced by the availability of badger burrows for nesting and, in turn, on predation pressures by badgers.
Humpback whales feed in several high‐latitude areas of the North Pacific. We examined the interchange of humpback whales between one of these areas, off California, and those in other feeding grounds in the eastern North Pacific:. Fluke photographs of 597 humpback whales identified off California between 1986 and 1992 were compared with those off Oregon and Washington (29); British Columbia (81); southeastern Alaska (343); Prince William Sound, Alaska (141); Kodiak Island, Alaska (104); Shumagin Islands, Alaska (22); and in the Bering Sea (7). A high degree of interchange, both inter‐and intrayear, was found among humpback whales seen off California, Oregon, and Washington., A low rate of interchange was found between British Columbia and California.: two whales seen near the British Columbia/Washington border were photographed off California in a different year, No interchange was found between California and the three feeding areas in Alaska. Humpback whales off California, Oregon, and Washington form a single intermixing feeding aggregation with only limited interchange with areas farther north. These findings are consistent with photographic identification studies in the North Atlantic and with genetic studies in both the North Atlantic and North Pacific.
As anthropogenic disturbances continue to drive habitat loss and range contractions, the maintenance of evolutionary processes will increasingly require targeting measures to the population level, even for common and widespread species. Doing so requires detailed knowledge of population genetic structure, both to identify populations of conservation need and value, as well as to evaluate suitability of potential donor populations. We conducted a range-wide analysis of the genetic structure of red foxes in the contiguous western U.S., including a federally endangered distinct population segment of the Sierra Nevada subspecies, with the objectives of contextualizing field observations of relative scarcity in the Pacific mountains and increasing abundance in the cold desert basins of the Intermountain West. Using 31 autosomal microsatellites, along with mitochondrial and Y-chromosome markers, we found that populations of the Pacific mountains were isolated from one another and genetically depauperate (e.g., estimated Ne range = 3–9). In contrast, red foxes in the Intermountain regions showed relatively high connectivity and genetic diversity. Although most Intermountain red foxes carried indigenous western matrilines (78%) and patrilines (85%), the presence of nonindigenous haplotypes at lower elevations indicated admixture with fur-farm foxes and possibly expanding midcontinent populations as well. Our findings suggest that some Pacific mountain populations could likely benefit from increased connectivity (i.e., genetic rescue) but that nonnative admixture makes expanding populations in the Intermountain basins a non-ideal source. However, our results also suggest contact between Pacific mountain and Intermountain basin populations is likely to increase regardless, warranting consideration of risks and benefits of proactive measures to mitigate against unwanted effects of Intermountain gene flow.
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