The risk of infanticide may alter foraging decisions made by females, which otherwise would have been based on nutritional requirements and forage quality and availability. In systems where meat resources are spatially aggregated in late summer and fall, female brown bears (Ursus arctos) would be faced with a trade-off situation. The need of reproductive females to accumulate adequate fat stores would likely result in a decision to frequent salmon streams and consume the protein- and lipid-rich spawning salmon. In contrast, aggregations of bears along salmon streams would create conditions of high risk of infanticide. We investigated consumption of salmon by brown bears on Admiralty and Chichagof Islands in Southeast Alaska from 1982 to 2000 using stable isotope analysis and radiotelemetry. While nearly all males (22 of 23) consumed relatively large amounts of salmon (i.e., >10% relative contribution to seasonal diet), not all females (n=56) did so. Five of 26 females for which we had reproductive data, occupied home ranges that had no access to salmon and thus did not consume salmon when they were mated or accompanied by young. Of females that had access to salmon streams (n=21), all mated individuals (n=16) had delta(15)N values indicative of salmon consumption. In contrast, 4 out of 16 females with cubs avoided consuming salmon altogether, and of the other 12, 3 consumed less salmon than they did when they were mated. For 11 of 21 females with access to salmon streams we had data encompassing both reproductive states. Five of those altered foraging strategies and exhibited significantly lower values of delta(15)N when accompanied by young than when mated, while 6 did not. Radiotelemetry data indicated that females with spring cubs were found, on average, further away from streams during the spawning season compared with females with no young, but both did not differ from males and females with yearlings and 2-year-olds. Females with young that avoided salmon streams were significantly lighter indicating that female choice to avoid consumption of salmon carries a cost that may translate to lower female or cub survivorship. The role of the social hierarchy of males and females, mating history, and paternity in affecting the risk of infanticide and foraging decisions of female brown bears merit further investigation.

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The conservation status of northern goshawks in southeast Alaska is examined through developing an understanding of goshawk ecology in relation to past, present, and potential future habitat conditions in the region under the current Tongass land management plan. Forest ecosystem dynamics are described, and a history of forest and goshawk management in the Tongass National Forest is reviewed. Nearly 900,000 acres of the most productive old-growth temperate rain forest in southeast Alaska (public and private lands) have been harvested during the past 90 years and changed to early seral conifer forests. Goshawk habitat relations are described through a review of the goshawk literature. Significant preliminary findings of a habitat relation study in southeast Alaska include the following: goshawks select productive old-growth forests with > 60 percent of all adult goshawk telemetry relocations occurring in this cover type; nonforest, clearcut, and alpine cover types were least used and were avoided relative to their availability; and the median breeding season minimum convex polygon use areas of adult goshawks was about 10,000 acres. Goshawks predominantly use gentle slopes (70 percent of relocations) at elevations below 800 feet (54-74 percent of relocations); 24 percent of relocations occurred in riparian habitat zones, and nearly 20 percent of all relocations occurred within the beach fringe habitat extending 1,000 feet inland from the ocean shoreline. Goshawk nesting habitat is a nonrandom subset of the landscape with a significantly higher proportion of productive old-growth forest within a 600-acre analysis area surrounding known nests. The probability of persistence of goshawks has declined over the past 50 years owing to habitat loss and likely will continue to decline under current management plan regimes; however, the goshawk population likely is not in immediate peril. The predicted consequences of several alternative habitat management approaches are compared. This analysis suggests that long rotation forestry (e.g., 300 years) and uneven-aged silvicultural management may maintain habitat characteristics important to sustaining goshawk populations well distributed across the region. Although habitat reserves are not considered an essential component of a forest-wide goshawk conservation strategy, reserves, in combination with extended rotations, may be important where the intensity of past management actions has precluded the opportunity to attain a desired combination of forest age classes achieveable under long rotations. Revision efforts for the TLMP resumed in fall 1994 with a focus on five major land management issues considered to be inadequately addressed in the existing TLMP: wildlife viability, fish and riparian habitat, caves and karst, alternatives to clearcutting, and socioeconomic considerations. Goshawk conservation is an important component within the wildlife viability issue.Concern for goshawk population viability in southeast Alaska evolved during the past decade and culminated with th...

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. A simulation study was undertaken to assess the sampling stability of the variable loadings in linear discriminant function analysis. A factorial design was used for the factors of multivariate dimensionality, dispersion structure, configuration of group means, and sample size. A total of 32 400 discriminant analyses were conducted, based on data from simulated populations with appropriate underlying statistical distributions. Ecological Society of AmericaResults from the simulations suggest that minimum sample sizes must exceed multivariate dimensionality by at least a factor of three to achieve reasonable levels of stability in discriminant function loadings. However, the requisite sample size would vary with respect to each of the design factors and, especially, with the overall amount of system variation.A review of 60 published studies and 142 individual analyses indicated that sample sizes in ecological studies often have met that requirement. However, individual group sample sizes frequently were very unequal, and checks of assumptions usually were not reported. We recommend that ecologists obtain group sample sizes that are at least three times as large as the number of variables measured.

Video recording of prey deliveries to nests is a new technique for collecting data on raptor diet, but no thorough comparison of results from traditional methods based on collections of prey remains and pellets has been undertaken. We compared data from these 3 methods to determine relative merits of different methods for assessing raptor diet as part of a study of the breeding‐season diet of northern goshawks (Accipiter gentilis) in Southeast Alaska. We applied these methods to 5 nests during each of the northern goshawk breeding seasons of 1998 and 1999 and identified 1,540 prey from deliveries, 209 prey from remains, and 209 prey from pellets. The proportions of birds and mammals varied among techniques, as did relative proportions of prey groups and age groups. Prey remains and pellets gave the least‐similar diet descriptions. Over 2‐day intervals during which data were collected using all 3 methods, prey‐delivery data gave more individual prey and prey categories than the 2 other sources of information. We found that prey were not directly tracked in either prey remains or pellets compared with prey delivery videography. Analysis of prey‐delivery videography provided the most complete description of diet, and we recommend that studies attempting to describe diet use this technique, at least as part of their methodology.