Foraging options of woodland caribou (Rangifer tarandus caribou) in the high snowpack ecosystems of western North America become narrowed. after freezing; temperatures in autumn precipitate leaf-drop in deciduous shrubs. The objectives of this research were to determine the influence of (1) removing arboreal lichen (Ascomycetes) on windthrown trees and myrtle boxwood. (Pachistima myrsinites) and (2) stand type (old-growth versus clearcut) on woodland caribou foraging dynamics during autumn. Foraging trials were conducted with 3 tame woodland. caribou in 6 0.5-ha pens. In 3 treatment pens all windthrown arboreal lichen-bearing trees were removed from the old-growth portion of tie pen and extant myrtle boxwood plants were removed from the entire pen. In the 3 control pens all extant windthrown trees and myrtle boxwood plants were retained. In addition, pens were constructed such that half of each pen was in an old-growth stand of western red-cedar (Thuja plicata)-Western hemlock (Tsuga heterophylla) and half was in an adjacent clearcut. Arboreal lichen had the greatest influence on dry-matter intake rate (DMIR) because of the large bite size provided by this forage. In control pens, caribou had higher DMIR (P = 0.006) and crude protein intake rate (CPIR) (P = 0.007) than in treatment pens where lichen-bearing windthrown trees had been removed, Arboreal lichen from windthrown trees was 52% (range = 43-64) of the total DMI in the old-growth portions of control pens. Arboreal lichen from windthrown trees comprised 81% (range = 75-92) of the arboreal lichen bites (i.e., 19% of arboreal lichen bites were from litterfall and standing trees), and 28% (range = 16-48) of total bites in the timbered portion of control pens. The DMIR (P = 0.004) and CPIR (P = 0.004) of caribou was also greater in old-growth than in clearcut portions of pens. Search time was greater (P = 0.003) in clearcut portions of pens than in old-growth portions. Myrtle boxwood comprised <0.4% of caribou diets. These data suggest that arboreal lichen is an important dietary component earlier in autumn than previously reported.

Statewide surveys conducted for northern goshawks (Accipiter gentilis) by the Washington Department of Fish and Wildhfe (WDFW) in the early 1990s had relatively low detection rates throughout the state and different rates of detection between easte n (1 bird/55 kn and western Washington (1 bird/174 km To investigate the possibility that survey methods or regional habitat characteristics affected detection rates, we tested broadeast calls at 40 nest stands known to be occupied by nesting northern goshawks. During 439 station visits and 210 trials, we recorded 109 detections, 68% of which were vocalizations. Northern goshawks at 37 of the 40 (93%) occupied territories re detected at least once, including 4 occupied sites that failed. Detectability was eater at successful nests Juvenile northern goshawks were more responsive than adults, which increased detection rates at successful nests by 37% during the postfledging period and accounted for 87% of responses. Logistic regression modeling identified distance of the surveyon to the nest as the only factor correlated with detection rates (P < 0.001). Probability of detecting northern goshawks at occupied stands increased as nests were approached from 400 m (0.20), 250 m (0.25), and 100 in (0.42). Binomial expansion of detection probabilities at a single nest visit found broadcasting to attain ≥90% detections required 5 visits at 100 m, 8 at 250 m, and 10 at 400 m. Because analysis of detection rates by area did not show an effect of vegetation screening, slope, or topography, differences in the relative abundance of northern goshawks from earlier surveys reflect true variation in abundance, differences in nest success, or some combination of both. Results lend more justification for use of broadcast calling for northern goshawk in Pacific Northwest torests and provide a hypothetical model for estimating survey costs as a function of detection probability, trial frequency, and station spacing.

12 Alces alces shirasi ont ete equipes d'emetteurs radio et suivis entre jan 1979 et avr 1982. Ils choississent les types de vegetation abondants en toutes saisons. L'habitat est choisi en fonction des saisons