Current harvest management of grizzly bears Ursus arctos in British Columbia (B.C.), Canada, is based primarily on modeling of habitat capability/suitability. No research has been conducted in the northern half of B.C. to verify these habitat-based estimates. We estimated grizzly bear population size in a 8,527 km² study area in northeastern B.C. that included the east slopes of the northern Rocky Mountains (Northern Boreal Mountains ecoprovince) and the boreal plains (Taiga Plains ecoprovince) using hair removal to sample bears, microsatellite profiling to identify individuals, and mark-recapture models. We placed bait sites encircled by barbed wire in a grid of 103 9 × 9 km (81 km²) cells. In each cell a different bait site was set for 12 days in each of five sessions. We collected 2,062 hair samples from 332 sites and detected grizzly bears at 113 sites. DNA profiling of grizzly bear samples identified 98 different bears; 44 of these individuals were females, 47 were males, and the remaining seven individuals could not be sexed. Forty-one grizzly bears were caught at >1 site. We used a closed mark-recapture model to obtain a naive population estimate of 148 grizzly bears (95% confidence interval (Cl): 124–182). We reduced this estimate by 6.8% to account for closure bias, which resulted in an adjusted population estimate of 138 grizzly bears (95% Cl: 114–172) within the study area (16 bears/1,000 km²; 95% Cl: 13–20). Within the two biophysical ecoprovinces we estimated a density (corrected for closure) of 29 bears/1,000 km² (95% Cl: 23–37) for the Northern Boreal Mountains and 10 bears/1,000 km² (95% Cl: 7–18) for the Taiga Plains. The current habitat-based capability ratings for grizzly bears in the boreal ecoprovinces of B.C. are supported by our results in the Taiga Plains, but are lower than densities we obtained in the Northern Boreal Mountains by about half. With further testing, habitat-based estimates of grizzly bear density in B.C. could be adjusted using the results of DNA-based population estimates.

Large carnivores are vulnerable to road effects because of their great mobility and extensive spatial requirements for survival. Wildlife crossing structures have mitigated harmful effects of roads for ungulate species, but there is limited information on how effective these structures are for large predators. We investigated the response of cougars Puma concolor to wildlife crossing structures along 45 kilometers of the Trans-Canada highway in Banff National Park, Alberta, Canada. Twenty-two crossing structures were monitored year-round for wildlife passage during 1996–2000. Cougar consistently used the wildlife crossing structures more than expected during winter months and less than expected during the summer. There was a significant positive correlation between passages made by cougar through wildlife crossing structures and those made by mule deer Odocoileus hemionus and white-tailed deer O. virginianus. There was no correlation between cougar and human use of the wildlife crossing structures. Cougar use of the five structure types differed from that expected. Open-span bridge underpasses were used more than expected, whereas creek bridge underpasses were used in proportion to their availability. All other crossing structure types were used significantly less than expected. The wildlife crossing structures that received the highest numbers of cougar passages were those situated close to high quality cougar habitat. The pattern of structure use was partly explained by the quality and distribution of cougar habitat near the structures as opposed to their physical features. Our results indicated that cougars tended to use underpasses more than wildlife overpass structures, and our study documents that cougars used crossing structures in a way that ensures habitat connectivity.

Arctic geese often use spring migration stopover areas when feeding habitats are partially snow covered. Melting of snow during the stopover period causes spatial and temporal variability in distribution and abundance of feeding habitat. We recorded changes in snow cover and lesser snow goose Anser caerulescens caerulescens distribution on a spring migration stopover area in south-central Alaska during aerial surveys in 1993–1994. Our objectives were to determine whether geese selected among areas with different amounts of snow cover and to assess how temporal changes in snow cover affected goose distribution. We also measured temporal changes in chemical composition of forage species after snow melt. We divided an Arc/Info coverage of the approximately 210 km² coastal stopover area into 2-km² cells, and measured snow cover and snow goose use of cells. Cells that had 10–49.9% snow cover were selected by snow geese, whereas cells that lacked snow cover were avoided. In both years, snow cover diminished along the coast between mid-April and early May. Flock distribution changed as snow geese abandoned snow-free areas in favour of cells where snow patches were interspersed with bare ground. Snow-free areas may have been less attractive to geese because available forage had been quickly exploited as bare ground was exposed, and because soils became drier making extraction of underground forage more difficult. Fiber content of two forage species increased whereas non-structural carbohydrate concentrations of forage plants appeared to diminish after snow melt, but changes in nutrient concentrations likely occurred too slowly to account for abandonment of snow-free areas by snow geese.

Though the occurrence of night time feeding has been demonstrated in numerous species of wildfowl, accurately quantifying this behaviour visually is inherently difficult and so alternative techniques are required. During the course of two distinct projects on the ecology of brent geese Branta bernicla in England (Studies A and B) and another in Germany (Study C) we used position-sensitive radio transmitters, attached to thin leather neck collars, to monitor feeding behaviour remotely. In this paper, we present a collective account of the method. Transmitter units emitted pulses at two different intervals depending on the orientation of a built-in tilt switch; generally shorter intervals (ca 1.1 seconds) when a bird lowered its neck to feed and longer intervals (ca 1.4 seconds) when in upright positions, though in some units this was reversed. Daytime observations of each radio-marked goose were required to produce predictive equations which described the proportion of time feeding in terms of mean pulse interval (Study B), number of long intervals between pulses (Study C) or the proportion of time in which pulses were received at short (or in some cases long) intervals (Study A). Coefficients of determination ranged within 0.13–0.95. These equations could be used to interpret data that was received and stored at regular intervals (30 or 60 seconds) during night time by a data logging system. Each study also assessed whether the collars affected the behaviour of the geese. No significant behavioural differences were observed for free-ranging birds wearing collars compared to nearby birds without. This technique is a realistic option for ecological studies of wildfowl requiring construction of feeding time budgets through the night as well as the day.

Low hatching success due to nest depredation has frequently been reported from waterfowl breeding sites, but current knowledge on relationships between duck nests and their predators, which should form a basis for successful management, remains incomplete. We used a 13-year data set to test whether specific predator species are more successful in finding certain types of natural duck nests and whether there are interspecific differences in nest characteristics. Multinomial logistic regression allowed simultaneous evaluation of the effects of different factors, including their interactions. Significant predictors of duck nest fate were the presence of water edge and 3-way interaction among presence of gull colonies, island type and clutch initiation date. Significant predictors of nest site use by duck species were: 3-way interaction among presence of gull colonies, island type and clutch initiation date, 3-way interaction among presence of gull colonies, island type and presence of water edge and 2-way interaction between presence of water edge and clutch initiation date. The above interactions led to certain associations between duck species and predator species. Corvids (hooded crow Corvus corone cornix and raven Corvus corax) were responsible for depredating more mallard Anas platyrhynchos nests, but fewer common pochard Aythya ferina and tufted duck Aythya fuligula nests than expected. American mink Mustela vison was responsible for destroying more small Anas species (northern shoveler Anas clypeata, garganey Anas querquedula and gadwall Anas strepera) and tufted duck nests, but fewer mallard nests than expected. Marsh harrier Circus aeruginosus was apparently a generalist predator since we were not able to detect significant associations between this predator and nests of any specific duck species. We believe that examination of interactions between different factors affecting the probability that nests will be either successful or depredated by certain predator species may help waterfowl managers increase management success.

Condition related pre-breeding hunting vulnerability in the common eider Somateria mollissima, i.e. the relationship between body condition attained as a duckling and the probability of being shot, was analysed from recoveries of hunter-retrieved birds ringed in the Stavns Fjord colony in Denmark during 1991–1995. Mean duckling cohort condition showed significant variation between years, but the proportions of birds retrieved during the first three seasons were similar (4.9% ± 1.4 SD). The proportion of birds retrieved by hunters declined from 3.9% in the first year to 0.64% and 0.38% in the second and third year, respectively. A condition bias was found in first-year retrieved birds in the cohorts with the highest and poorest mean condition, but not in the cohorts of intermediate condition. In accordance with a priori predictions regarding condition related non-hunting mortality during the period between marking and the opening of the hunting season, the direction of the bias was negative (hunters retrieved poor individuals compared to cohort mean) in the cohort of high mean condition, and positive (hunters retrieved good individuals compared to cohort mean) in the cohort of poor mean condition. Despite significant variation in cohort condition, the duckling condition of individuals retrieved during their first season from the cohorts of high and poor mean condition was comparable. The condition of first-year retrieved birds was not significantly different from the condition of birds retrieved during their second and third year, when all years were pooled. As there is a significant positive relationship within cohorts between duckling condition and recruitment of (female) eiders, the present results suggest, 1) that hunting vulnerability in the eider is related to a specific (poor) level of body condition attained prior to fledging, and 2) that hunting tends to remove the poorest individuals present at the time when the hunting season opens.