Distribution of the Central Arctic caribou herd is characterized by segregation of the sexes and different habitat preferences by male and female caribou over most of the annual cycle. During all periods except late winter and postcalving, females showed a more northern distribution than did males. Females used riparian habitats less than availability and were generally farther from major river valleys than expected during all seasons except late winter. In contrast, males preferred riparian habitats from late winter to calving and were generally found closer to river valleys than were females from late winter to August dispersal. During the spring and calving periods near the coast females preferred sedge meadow and used riparian habitat less than availability whereas males preferred riparian and tussock tundra and used sedge meadow less than availability. It is theorized that sexual segregation and differential habitat use reflect predator avoidance strategies of females with calves and optimal foraging by adult males.
A photographie census of the Rivière George caribou herd in Quebec and Labrador was conducted between 4-23 July 1993 during the post-calving period. The primary objective of the study was to obtain an accurate estimate of the current size of the herd to permit the monitoring of population trends and effective management of the herd. The census procedure consisted of (1) use of satellite and conventional radio-telemetry to locate and photograph post-calving aggregations during the period of optimal aggregation, (2) determination of the minimum population size by direct counts from photographs, and (3) estimation of the total population size using the Petersen Index method. This method allowed extrapolation of the data to caribou that were either not photographed or that were not aggregated at the time of the census. The minimum count indicates that the Rivière George caribou herd consisted of at least 358 460 adults (older than calves) at the time of the census. This count underestimates the total population size but is useful because it is virtually free of error. The total size of the Rivière George herd in July 1993 was estimated to be 540 040 adults within 90% confidence limits of + 12.8%. Comparisons with previous estimates indicate that the size of the herd continues to be large, but that its growth has probably ceased. This study demonstrates that a photographic survey of post-calving aggregations is an effective method to census the Rivière George herd and possibly other large migratory caribou herds that are monitored by telemetry.
Use of bacterial insecticides containing Bacillus thuringiensis var. kurstaki (Btk) is gaining popularity as an environmentally safe control measure against lepidopteran pests, but indirect effects on nontarget organisms through reduced prey base have received little attention. Aerial spraying of Btk (Foray 48B) over a 12,803-ha area on southeastern Vancouver Island (BC, Canada) in May to June 1999 as part of a gypsy moth (Lymantria dispar) control program provided us with an opportunity to examine the responses of songbirds to spray application. To obtain an estimate of species richness and relative abundance, we conducted standard songbird point-count surveys in Garry oak (Quercus garryana)-dominated habitats in Btk-sprayed and unsprayed areas in April to June 1999 and, one year after spraying, in 2000. These surveys revealed no patterns consistent with adverse effects of spraying on the relative abundance of adult birds or singing males for any of the species, whether examined individually or when combined into foraging guilds. An exception was the spotted towhee (Pipilo maculatus), which in 1999, but not in 2000, occurred at significantly lower numbers in sprayed plots after Btk treatment. Intensive searches of plots in sprayed and unsprayed areas revealed no differences in the numbers of songbird broods between the two areas for any of the species examined.
Eight of 31 radio-tagged female blue grouse (Dendragapus obscurus) that had first nests terminated before hatch produced second clutches. Significantly more adult than yearling hens renested. All yearling hens that produced a second clutch had first nests terminated during laying or early incubation; but most yearlings did not renest. Adult females renested independently of the stage of incubation when nests were terminated. Average size of second clutches of adults are likely larger than those of yearlings and average size of second clutches of all females are likely smaller than those of first clutches. Most prenesting home ranges used during second nesting attempts were in the same general areas and of the same sizes as those used during initial nesting attempts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.