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Calvin J. Lensink

Publications and source records attributed to Calvin J. Lensink.

7 recordsLinked to original sources
USGS1993

Age-specific reproduction in female sea otters (Enhydra lutris) from south-central Alaska: Analysis of reproductive tracts

We estimated age at sexual maturity and age-specific reproductive rates by examining carcasses and reproductive tracts from 177 female sea otters (Enhydra lutris ). Carcasses were recovered from south-central Alaska, Primarily from western Prince William Sound, as a result of the T/V Exxon Valdez oil spill in 1989. We found 65% of our sample to be sexually mature. Sexual maturity was first attained at age 2. The proportion of sexually mature animals increased from 30% at age 2 to 100% at age 5. Annual reproductive rates increased from 22% at age 2 to 78% at age 5 and remained relatively stable (75-88%) through to age 15. the sex ratio (female:male) of 49 fetal sea otters was 18:37 and differed significantly from parity. Females younger than 8 tended to produce more female fetuses, while older mothers did not. Our estimates of the reproductive characteristics of female sea otters obtained by examination of reproductive tracts were similiar to those reported in the literature based on in situ observations of marked individuals.

Alaska↗
USGS1993

Current status and recent dynamics of the Black Brant Branta bernicla breeding population

We summarize current knowledge about the distribution of Pacific Black Brant and recent dynamics of colonies, particularly on the Yukon-Kuskokwim (Y-K) Delta, Alaska. About 20,000 nests are required to produce the number of young in the autumn flight using estimates of clutch size, hatching success and gosling survival based on colonies on the Y-K Delta. More than 80% of the nests in the population can be accounted for currently on the Y-K Delta. Most moulting individuals that did not breed, or were unsuccessful, are unaccounted for in late summer. Numbers of Black Brant nesting in major colonies on the Y-K Delta declined >60% in the early 1980s, most likely as a result of local subsistence harvest combined with predation by arctic foxes. Effective management of this population requires a better understanding of the distribution of breeding and moulting birds, the importance of breeding habitat to colony dynamics and the role of both sport and subsistence harvest in population dynamics.

Wildfowl↗
USGS1990

Procedures and rationale for marking sea otters captured and treated during the T/V Exxon Valdez oil spill

Four methods were used for marking sea otters ( Enhydra lutris ) captured and treated during the response to the T/V Exxon Valdez oil spill. Colored and numbered flipper tags were placed on each sea otter that was brought to the otter treatment centers. These tags allowed individual recognition and permitted the tracking of individuals through the treatment and holding processes. Recovery of tagged carcasses may provide a crude measure of the fates of rehabilitated otters. Seven sea otters were instrumented with radio transmitters attached to flipper tags as part of a pilot release program. The results of that study were inconclusive. Forty-five sea otters were implanted with radio transmitters as part of a study to assess the fate of rehabilitated sea otters. Specific objectives of the study include estimating survived rates and monitoring the reproductive success of the sample of rehabilitated sea otters and comparing the results with similar variables in a control population. Transponder chips were injected in the perianal region of all but seven of the instrumented sea otters, and all were tagged with red flipper tags. The advantages and disadvantages of each type of tag are discussed.

Alaska↗
USGS1988

Survival of aluminum and monel bands on black brant

Three recoveries of Black Brant ( Branta bernicla nigricans ) were recently reported in the "Significant Encounters" section of North American Bird Bander (Anon. 1986). At the time of recovery these Brant were 21.5, 22 and at least 22.5 years old. The significance of these recoveries caught my attention as all were of birds banded on the Yukon Delta, Alaska in 1963 by the Alaska Department of Fish and Game. In that year bands made of monel metal, a corrosion-resistant alloy consisting mainly of nickel and copper, were used for the first time in anticipation that they would survive significantly longer than standard aluminum bands in the estuarine and marine habitats used by Brant. Follow-up studies of the experimental banding were conducted by the Yukon Delta National Wildlife Refuge of which I was manager from 1964-1975.

North American Bird Bander↗
USGS1986

Evaluation of Alaskan wetlands for waterfowl

Few studies have focused specifically on use of Alaskan wetlands by waterfowl. However, substantial information on the values of wetlands is available from studies on individual species or that were conducted for other purposes. Most investigators have found it most effective to classify habitat use on the basis of observed distribution patterns of waterfowl in relation to local physiographic features and vegetation types. Major variations in habitat among regions result from differences in precipitation, summer temperature, length of frost free period, and presence of permafrost. Large areas of intertidal habitat, usually associated with river deltas, are of key importance wherever they occur. Lakes subject to extensive periods of draw-down or that fluctuate with river systems are more productive than those with more stable water levels.

Conference Paper↗
USGS1981

An annotated bibliography of literature on Alaska water birds

The demand for information on birds in Alaska has surged within the past few years, primarily because of the need to adequately assess the impacts of a wide range of planned developments. The accompanying increase in studies of avian populations has resulted in a growing need for a comprehensive bibliography of Alaska ornithology. An initial effort by Bartonek and Lensink (1978) provided a list of published and unpublished references on marine birds, but this list was only marginally useful because it lacked adequate indexing and annotation of references cited. Their bibliography, however, plus those of Cade (1953) and Gabrielson and Lincoln (1959), provided the basis and primary reference sources for our work. In the present bibliography we have attempted to compile all substantive references addressing water birds in Alaska because this group of birds appears to be most Vulnerable to repercussions of development, particularly along the coast. However, the works cited make up an estimated 70-80% of all literature on birds in Alaska, and this volume thus provides an initial source of references on terrestrial birds. This bibliography, which contains 1554 citations, is current for most journal sources through 1979 and most of 1980. The content of each paper has been summarized, and we have indexed the citations by subject, species, and geographic location to make the bibliography a more useful reference. Furthermore, the bibliography has been designed to facilitate future inclusion of references that have been omitted or that will be published in the rapidly growing body of literature on Alaska birds.

Alaska↗