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1992

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Full-Text Articles in Population Biology

Management Plan Kimberley Prawn Fishery., G. Stewart Dec 1992

Management Plan Kimberley Prawn Fishery., G. Stewart

Fisheries Management Papers

This report outlines a management plan for the Kimberley Prawn Fishery which operates in Western Australia coastal waters of the Indian Ocean and Timor Sea, off the Kimberley coastline lying east of Koolan Island, 1230 45' east longitude and west of Cape Londondery, 1260 58' east longitude. Kimberley Prawn Fishery access restrictions were first specified in Western Australian Fisheries Notice No. 170 published in Governement Gazette No. 2 of 4 January, 1985. Present exploitation is low and access is limited to Western Australian Fishing Boat licences endorsed with transferable access to the Kimberley Prawn Fishery (9 trawlers) Trawlers with access …


The Cockburn Sound Fishery Management Plan. Summary Of Submission And Final Recommendations For Management., A. Millington Oct 1992

The Cockburn Sound Fishery Management Plan. Summary Of Submission And Final Recommendations For Management., A. Millington

Fisheries Management Papers

Identifiable "unit" fisheries in Cockburn Sound are: Beach bait fishing netting Fish set netting Crab netting Mussel diving Line fishing and pot fishing This report recommends measures for the longer term management of these fisheries In particular, that they be managed as limited entry fisheries under Section 32 of the Fisheries Act 1905. Strict entry criteria are proposed for continued access to these fisheries. Rules are proposed for boat replacement. Licence transferability is considered in detail. No decisions to be made on the policy for licence transfers until the final number of participants in each fishery is determined. Owner operation, …


Hawaiian Freshwater Fishes (Osteichthyes, Gobioidei) A Field Key To The Species Of Larvae And Postlarvae During Recruitment Into Fresh Waters, David C. Tate, J. Michael Fitzsimons, Richard P. Cody Jul 1992

Hawaiian Freshwater Fishes (Osteichthyes, Gobioidei) A Field Key To The Species Of Larvae And Postlarvae During Recruitment Into Fresh Waters, David C. Tate, J. Michael Fitzsimons, Richard P. Cody

Occasional Papers of the Museum of Natural Science, Louisiana State University

No abstract provided.


Seasonal Changes In Brown Adipose Tissue And Pelage Of The Southern Short-Tailed Shrew Blarina Carolinensis, Elisa Michelle Dew Jul 1992

Seasonal Changes In Brown Adipose Tissue And Pelage Of The Southern Short-Tailed Shrew Blarina Carolinensis, Elisa Michelle Dew

Biological Sciences Theses & Dissertations

Winter survival mechanisms in the southern short-tailed shrew, Blarina carolinensis, were studied by examining cellular changes in interscapular brown adipose tissue (ISBAT) and pelage characteristics in specimens collected each month of the year in eastern Virginia. On capture, each specimen was anesthetized with ether and then perfused with a 2.5% glutaraldehyde-2% formaldehyde solution. ISBAT tissues were examined histologically with the transmission electron microscopy. Because BAT is know to produce heat by nonshivering thermogenesis and is more developed in winter animals than summer animals, it was hypothesized that mitochondrial area of BAT would be relatively greater in winter than in summer. …


Rock Lobster Industry Advisory Committee Report To The Minister For Fisheries April 1992, Rock Lobster Industry Advisory Committee Apr 1992

Rock Lobster Industry Advisory Committee Report To The Minister For Fisheries April 1992, Rock Lobster Industry Advisory Committee

Fisheries Management Papers

The Committee recommended: For the next five seasons the principal tools of management for the rock lobster fishery should be temporary and variable reductions in pot usage, without affecting the permanent pot entitlement of any operator. The number of pots a fisherman can use at any particular time within a season will be set in accordance with a schedule showing the total permanent pot authorisation and the number of pots permitted to be used. Maximum size controls. These sizes would be 120 mm for females and 130 mm for males north of Moore River and about 125 mm for females …


Survey Of Mollusks Of The Platte River: Final Report, Patricia W. Freeman, Keith Perkins Mar 1992

Survey Of Mollusks Of The Platte River: Final Report, Patricia W. Freeman, Keith Perkins

School of Natural Resources: Faculty Publications

A survey of the mollusks of the Platte River was carried out during the summers of 1990 and 1991. With the exception of the Big Bend Reach of the River in Dawson, Buffalo and Hall counties, no unionids (mussels) were found in the main channel of the river. We found 11 species of mussels along the river and 16 species of snails at 49 different sites from east to west across the state. We found the Asiatic clam, a known, non-native, pest species, for the first time in the state placing it several hundred miles west of the present eastern …


Effects Of Moose Foraging On Browse Availability In New Hampshire Deer Yards, Michael T. Pruss, Peter J. Pekins Jan 1992

Effects Of Moose Foraging On Browse Availability In New Hampshire Deer Yards, Michael T. Pruss, Peter J. Pekins

New Hampshire Agricultural Experiment Station Publications

Food habits of moose (Alces alces) and white-tailed deer (Odocoileus virginianus) overlap in northern New Hampshire during autumn and winter. High moose and deer densities in deer yards, where deer may be confined for extended periods, could result in competition for limited deciduous forage. The purpose of this study was to investigate possible impacts by moose on browse availability in deer yards, and the potential effects on deer. Fifteen deer yards were studied in northern New Hampshire during spring and fall, 1990-91. Unbrowsed and browsed deciduous twigs, and deer and moose pellet groups were counted on 900 permanent plots to …


Status, Production And Migration Of Greater Sandhill Cranes On Agassiz National Wildlife Refuge, Minnesota, Jon J. Dimatteo Jan 1992

Status, Production And Migration Of Greater Sandhill Cranes On Agassiz National Wildlife Refuge, Minnesota, Jon J. Dimatteo

Proceedings of the North American Crane Workshop

Greater sandhill cranes (Grus canadensis tabida) nesting at Agassiz National Wildlife Refuge (NWR) in northwestern Minnesota were studied from 20 April 1984 to 10 December 1985. Local birds were monitored to determine population size and age structure, reproductive success, and migration routes and wintering grounds. Forty-two pairs were identified. Thirty-four were breeding pairs and 3 were subadult (nonbreeding) pairs. Twenty nests were found; pairs at 13 of these hatched at least 1 young. Forty-three pairs hatched a minimum of 62 young, and 28 pairs fledged 42 of 47 young. Fifteen birds were colormarked, 8 of which were radio-tagged …


An Evaluation Of Three Areas For Potential Populations Of Whooping Cranes, Janet L. Mcmillen, Stephen A. Nesbitt, Mary A. Bishop, Alan J. Bennett, Laurel A. Bennett Jan 1992

An Evaluation Of Three Areas For Potential Populations Of Whooping Cranes, Janet L. Mcmillen, Stephen A. Nesbitt, Mary A. Bishop, Alan J. Bennett, Laurel A. Bennett

Proceedings of the North American Crane Workshop

Sandhill crane (Grus canadensis) populations were evaluated on the Seney NWR, Michigan, the Okefenokee Swamp, Georgia, and in southcentral Florida to evaluate their suitability to support introduced whooping cranes (G. americana). This paper compares data collected at these sites and additional data collected in northcentral Florida. The length of the egg-laying period varied from 4.5 months in central Florida to 1 month at Seney, but egg-laying ceased at all sites from mid-May to early June. Mean clutch sizes were similar 0.7-1.9). Renesting ranged from 79% in northcentral Florida to <=5% at Seney. These dates and values are consistent with nesting successes that ranged from 48% in northcentral Florida to 80% at Seney. Average annual recruitment, 12.3 juveniles/lOa adults, was highest on the Kissimmee Prairie in southcentral Florida. Average annual horne range size for the non-migratory populations were 1 km2 on the Okefenokee and 6.6 km2 on the Kissimmee. Nesting season horne range sizes ranged from 0.5 km2 on the Okefenokee to 1.8 km2 at Seney. All candidate populations successfully satisfied most of the guidelines for potential whooping crane populations as established by the Whooping Crane Recovery Team. Once reintroduction techniques have been refined, any or all of the study sites have the capacity to accommodate a flock of whooping cranes commensurate with Whooping Crane Recovery Team recommendations.


A Microcomputer Data Base For Managing Whooping Crane Observation Records, Duane A. Asherin, David B. Hamilton, Wendy M. Brown, Roderick C. Drewien Jan 1992

A Microcomputer Data Base For Managing Whooping Crane Observation Records, Duane A. Asherin, David B. Hamilton, Wendy M. Brown, Roderick C. Drewien

Proceedings of the North American Crane Workshop

A database called WHOOPER contains whooping crane (Grus americana) observations for the Rocky Mountain foster-parent population and currently consists of 1,438 observations covering the period 1975-1987. The dBase III Plus database management system for microcomputers is used for the application. This description of the data base and its capabilities updates the prototype database described in the 1985 Crane Workshop.


Unobstructed Visibility At Whooping Crane Roost Sites On The Platte River, Nebraska, Craig A. Faanes Jan 1992

Unobstructed Visibility At Whooping Crane Roost Sites On The Platte River, Nebraska, Craig A. Faanes

Proceedings of the North American Crane Workshop

Unobstructed visibility is an important component of whooping crane (Grus americana) roosting habitat. Recent habitat modeling efforts suggest that unobstructed horizontal visibility is suitable at a minimum of 335 m. Unobstructed upstream and downstream visibility is also an important part of whooping crane roosting habitat, but quantification of that parameter has not been reported previously, or incorporated into species models. Data from the Platte River suggest that a minimum of 732 m of unobstructed upstream and downstream visibility is needed at whooping crane roost sites.


Crane Propagation At Miami Metro Zoo, 1983–1987, Carol G. Hesch Jan 1992

Crane Propagation At Miami Metro Zoo, 1983–1987, Carol G. Hesch

Proceedings of the North American Crane Workshop

Five species of cranes are bred at Miami Metrozoo. Few health problems have been encountered in raising a large number of chicks. Rearing cranes in close confinement, with limited resources, requires sound management and careful observation.


Sandhill Crane Surveys In The Northern Interior Highlands Of Mexico, Roderick C. Drewien, Wendy M. Brown, Elwood G. Bizeau Jan 1992

Sandhill Crane Surveys In The Northern Interior Highlands Of Mexico, Roderick C. Drewien, Wendy M. Brown, Elwood G. Bizeau

Proceedings of the North American Crane Workshop

Most sandhill cranes (Grus canadensis) wintering in Mexico are found in the northern Interior Highlands of Chihuahua. We surveyed sandhill cranes in the states of Chihuahua and occasionally Durango, Mexico, in winters 1972-90. The population averaged 23,106 (SD = 10,369) in 11 counts at 5-6 areas in Chihuahua. Laguna de Babicora, the most important wetland for cranes wintering in Mexico, had the largest numbers (X = 16,012), followed by Ascension (x = 2,405) and Laguna de los Mexicanos (x = 1,468). All 3 migratory subspecies were present. The lesser subspecies (G. c. canadensis) comprised 85.7% of …


Preliminary Identification Of Whooping Crane Staging Areas In Prairie Canada, Brian W. Johns Jan 1992

Preliminary Identification Of Whooping Crane Staging Areas In Prairie Canada, Brian W. Johns

Proceedings of the North American Crane Workshop

For 60 years a passive program has been in effect to monitor the migration of whooping cranes (Grus americana) through Saskatchewan, and currently the Canadian Wildlife Service coordinates a triprovincial reporting network and operates a telephone Hot Line to receive reports of sightings of migrating cranes. Analyses of historical data reported through those efforts have identified the chronology of migration, the migration corridor through Canada, and major staging/ stopover areas in Saskatchewan. Investigations are continuing to identify specific roost sites, feeding areas and the availability of suitable habitat within the staging/ stopover area.


Isolation-Rearing Of Siberian Crane Chicks At The International Crane Foundation, Meenakshi Nagendran, Robert H. Horwich Jan 1992

Isolation-Rearing Of Siberian Crane Chicks At The International Crane Foundation, Meenakshi Nagendran, Robert H. Horwich

Proceedings of the North American Crane Workshop

Three Siberian crane (Grus leucogeranus) chicks hatched in the summer of 1987 at the International Crane Foundation (lCF); Baraboo, Wisconsin, were raised in near-complete isolation from humans. The chicks were exposed to species-specific models, vocalizations, a costumed "parent" and a role-model adult Siberian crane housed in an adjacent pen. Attachment to costumed "parent," interchick interaction, and reactions to humans were measured and compared with those aspects of sandhill crane behavior under similar rearing conditions.


Re-Pairing Of Whooping Cranes At Aransas National Wildlife Refuge, Thomas V. Stehn Jan 1992

Re-Pairing Of Whooping Cranes At Aransas National Wildlife Refuge, Thomas V. Stehn

Proceedings of the North American Crane Workshop

Adult whooping cranes (Grus americana) on the winter range at Aransas NWR without mates may re-pair over a period of several months, while others remain un-paired throughout the winter. However, 1 association formed during the winter did not result in a pair bond.


Habitat Use By Florida Sandhill Cranes On The Kissimmee Prairie In Central Florida, Mary Anne Bishop Jan 1992

Habitat Use By Florida Sandhill Cranes On The Kissimmee Prairie In Central Florida, Mary Anne Bishop

Proceedings of the North American Crane Workshop

Radio-tagged Florida sandhill cranes (Grus canadensis pratensis) were monitored for habitat use during 1985 and 1986 on the Kissimmee Prairie in central Florida. For both breeding and nonbreeding cranes, 93 % of the daytime locations were in 3 habitat types: cropland and plowed pasture, improved pasture, and palustrine emergent wetlands. Improved pasture was the most frequently used daytime habitat for both social classes. Radio locations were divided among 4 time blocks (3 diurnal, 1 nocturnal) and 4 3-month seasons. Time-of-day effects for use of wetlands and improved pasture were only marginally significant (1' < 0.08 and l' < 0.09, respectively) for breeders and not significant (1' < 0.30 and l' < 0.43, respectively) for nonbreeders. There was no significant difference in habitat use by breeders among seasons. Chi-square analyses of diurnal locations indicated that 4 of the 6 breeding cranes monitored used palustrine emergent wetlands more than their availability. The selection for wetlands reflects not only the rich food sources available, but also their use as midday loafing and drinking sites and as a source of cover that the upland habitats do not offer.


Cranes And Power Lines: An Analysis Of The Issue, Craig A. Faanes, Douglas H. Johnson Jan 1992

Cranes And Power Lines: An Analysis Of The Issue, Craig A. Faanes, Douglas H. Johnson

Proceedings of the North American Crane Workshop

As part of a 1980-82 study, the flight behavior and mortality of sandhill cranes (Grus canadensis) was studied at 4 alkaline lake sites in central North Dakota. We analyzed the behavioral response of sandhill cranes in flight at powerline sites and examined factors associated with collisions with a power line structure. Several methods that can be used to reduce crane mortality at power line sites are discussed. Findings of several other research efforts that address crane mortality at power lines are summarized.


Population Status, Hunting Regulations, Hunting Activity, And Harvests Of Mid-Continent Sandhill Cranes, David E. Sharp, William D. Vogel Jan 1992

Population Status, Hunting Regulations, Hunting Activity, And Harvests Of Mid-Continent Sandhill Cranes, David E. Sharp, William D. Vogel

Proceedings of the North American Crane Workshop

The mid·continent population of sandhill cranes (Grus canadensis) was protected from 1916 until 1961, when hunting resumed on a limited basis. Areas open to hunting were experimentally expanded during 1961-72, but during the subsequent 1975-90 period only minor changes were made in the 8 Central Flyway states that established hunting seasons. Annual spring surveys conducted during 1982-90 indicated the population was stable at objective levels, with spring populations estimated at about 540,000 and fall flights near 590,000. Special federal hunting permits have been required for all bunters participating in regular seasons in the Central Flyway since 1975, where …


Contaminants In Habitat, Tissues, And Eggs Of Whooping Cranes, James C. Lewis, Roderick C. Drewien, Ernie Kuyt, Charles Sanchez Jr. Jan 1992

Contaminants In Habitat, Tissues, And Eggs Of Whooping Cranes, James C. Lewis, Roderick C. Drewien, Ernie Kuyt, Charles Sanchez Jr.

Proceedings of the North American Crane Workshop

Sampling of contaminants in the principal habitat areas of whooping cranes (Grus americana) of both the Rocky Mountain and the Aransas/Wood Buffalo National Park whooping crane populations began in the mid-1980's. Contaminants in eggs and tissues of whooping cranes were sampled opportunistically since the 1960's. Chlorinated hydrocarbons existed in low levels in the environment. Some trace elements including aluminum, arsenic, cadmium, chromium, copper. mercury, selenium, and zinc are of sufficient abundance to justify continued monitoring. Declines over time in residues of DDT and mercury in tissues and eggs reflected the prohibition in use of these as pesticides or …


Progress In Satellite Tracking Cranes, David H. Ellis, Dwight G. Smith, Glenn H. Olsen, Mark R. Fuller, Steven E. Landfried, Hiroyoshi Higuchi, Charles H. Vermillion Jan 1992

Progress In Satellite Tracking Cranes, David H. Ellis, Dwight G. Smith, Glenn H. Olsen, Mark R. Fuller, Steven E. Landfried, Hiroyoshi Higuchi, Charles H. Vermillion

Proceedings of the North American Crane Workshop

We review the history of tracking cranes with satellite telemetry and identify some of the difficulties in designing satellite transmitters and harnesses for cranes. Miniaturization of these transmitters and a plethora of harnessing experiments since 1989 allow us to recommend limited application of this technology to all species of cranes. We are still uncertain, however, if cranes harnessed with satellite telemetry devices are able to reproduce after migration. Because of this uncertainty, we urge caution in the use of this technology, especially with breeding adults in severely endangered popUlations. This manuscript also describes continuing research needs.


Proceedings Of The Sixth North American Crane Workshop Jan 1992

Proceedings Of The Sixth North American Crane Workshop

Proceedings of the North American Crane Workshop

In 1975 a group of North American crane researchers and managers convened a workshop at the fledgling International Crane Foundation in Baraboo, Wisconsin. At the end they agreed to publish the proceedings of the workshop and to reconvene in 3 years to continue to share information, ideas, and support. Workshops followed in 1978 (Rockport, Texas), 1981 (Grand Teton National Park, Wyoming), 1985 (Grand Island, Nebraska), and 1988 (Kissimmee Prairie, Florida). At the Florida meeting this loose-knit group agreed to form the North American Crane Working Group (NACWG), an organization of "professional biologists, aviculturists, land managers, and other interested individuals dedicated …


Sexual Size Dimorphism And Size Indices Of Six Species Of Captive Cranes At The International Crane Foundation, Scott R. Swengel Jan 1992

Sexual Size Dimorphism And Size Indices Of Six Species Of Captive Cranes At The International Crane Foundation, Scott R. Swengel

Proceedings of the North American Crane Workshop

Sexual size dimorphism and size indices in captive cranes were studied to learn dimorphism patterns and size relationships that could be used in the management of captive cranes. In 6 species of captive cranes. Siberian (Grus leucogeranus), eastern sarus (G. antigone sharpir), white-naped (G. vipio), common (G. grus), hooded (G. monacha), and red-crowned (G. japonensis), maIes averaged 14.5-28.5% heavier than femaIes (P < 0.05) in all species. MaIes had longer culmens, tarsi, and wing chords in all species. MaIes had significantly longer culmens (P < 0.05) in 4 of 6 species and had significantly longer tarsi than females (P < 0.05) in 3 of 6 species. Culmen and tarsus lengths both averaged 7% longer in males than females when the 6 species were combined. Wing chord length was not significantly dimorphic (P > 0.05) in any of the 4 species measured (Siberian, white-naped, hooded, and red-crowned cranes), averaging only 1.3 -3.3 % longer in males than in females. Body …


Dispersal Of Pen-Reared Mississippi Sandhill Cranes, Phillip J. Zwank, Donna A. Dewhurst Jan 1992

Dispersal Of Pen-Reared Mississippi Sandhill Cranes, Phillip J. Zwank, Donna A. Dewhurst

Proceedings of the North American Crane Workshop

Dispersal patterns of juvenile parent-reared, captive produced Mississippi sandhill cranes (grus canadensis pulla) were monitored using radiotelemetry. Dispersal chronology and distance traveled by cranes differed among 4 releases and seemed to be influenced by rearing methods. Most cranes that had been placed in communal pens before release formed flocks when released. Cranes released without communal pen experience did not flock, but individually associated with native cranes. Nonflocking released cranes dispersed more rapidly and to a greater distance, but had lower survival.


Satellite Tracking Of A Greater Sandhill Crane, Meenakshi Nagendran Jan 1992

Satellite Tracking Of A Greater Sandhill Crane, Meenakshi Nagendran

Proceedings of the North American Crane Workshop

The first satellite transmitter (PTT) to be used on a wild crane was deployed on an isolation-reared greater sandhill crane (Grus canadensis tabida) colt in south Texas on 6 November 1988. The 160-g transmitter required more than 8 hours of direct sunlight for the solar cells to recharge the NiCad battery power supply. Signal repetition rate was once every 60 seconds. National Oceanic and Atmospheric Agency satellites in polar orbits, equipped with Argos instruments, received PIT signals via a doppler shift mechanism. Information included location of PTT (bird), long-term activity, short-term activity, and ambient temperature. The crane colt …


Effects Of Extended On Sandhill Crane Reproduction, George F. Gee, Grey W. Pendleton Jan 1992

Effects Of Extended On Sandhill Crane Reproduction, George F. Gee, Grey W. Pendleton

Proceedings of the North American Crane Workshop

Photoperiod studies were conducted with greater sandhill cranes (Grus canadensis tabida) from 1969 to 1972 and from 1982 to 1987 at the Patuxent Wildlife Research Center, Maryland. When housed indoors and exposed to long photoperiods, males produced semen during winter. When exposed to artificially extended photoperiods during spring in outdoor pens, females apparently laid earlier in the year and laid more eggs than they would have without the added light. Cranes did not exhibit any signs of photo refractory response to extended photo periods.


Capturing Whooping Cranes And Sandhill Cranes By Night-Lighting, Roderick C. Drewien, Kent R. Clegg Jan 1992

Capturing Whooping Cranes And Sandhill Cranes By Night-Lighting, Roderick C. Drewien, Kent R. Clegg

Proceedings of the North American Crane Workshop

We caught 19 adult (> 1.5 years old) whooping craoes (Grus americana) in 84 capture attempts (23 % success) by nightlighting during 1981-91 in Idaho, Wyoming, and New Mexico, including 17 for experimental purposes and 2 that were debilitated (aviao cholera aod lead poisoning). We also captured 250 greater saodhill craoes (G. canadensis tabida), including 157 adults aod 93 juveniles, on summer areas at Grays Lake National Wildlife Refuge, Idaho, to color-mark them for behavioral and movement studies. Night-lighting equipment included an 8.5-kg portable generator mounted on an aluminum back-pack frame and a 12- or 28-V …


Habitat Use By Greater Sandhill Cranes In Wyoming, Mary M. Rowland, Lynn Kinter, Tim Banks, David C. Lockman Jan 1992

Habitat Use By Greater Sandhill Cranes In Wyoming, Mary M. Rowland, Lynn Kinter, Tim Banks, David C. Lockman

Proceedings of the North American Crane Workshop

Wyoming suppors approximately 20% of the Rocky Mountain population (RMP) of greater sandhill cranes (Grus canadensis tabida), as well as a number of whooping cranes (Grus americana) from the Grays Lake, Idaho flock. Cranes begin arriving on post-migration staging areas in Wyoming in mid-March and disperse to summer habitat in April or May, depending on snow cover. Fall pre-migration, staging peaks around mid-September; most cranes leave the state by 1 October. Wet meadows and gram fIelds were the major habitat types used by cranes in Wyoming 1985-1987. Use in these types ranged from 69- 100% of …


Proceedings 1988 North American Crane Workshop Jan 1992

Proceedings 1988 North American Crane Workshop

Proceedings of the North American Crane Workshop

What follows is the published product of the fifth North American Crane Workshop held February 22-24, 1988, at River Ranch Outdoor Resort, Lake Wales, Florida. These papers were among the 52 given during that workshop. Also at this meeting, the North American Crane Working Group came into being with the election of a board of directors and the group's first president, Gary Lingle. Among other things, the working group will oversee and lend continuity to future workshops and the publication of the proceedings.

The meeting was organized by the Florida Game and Fresh Water Fish Commission with support from the …


Mortality In Fledged Whooping Cranes Of The Aransas/Wood Buffalo Population, James C. Lewis, Ernie Kuyt, Kenneth E. Schwindt, Thomas V. Stehn Jan 1992

Mortality In Fledged Whooping Cranes Of The Aransas/Wood Buffalo Population, James C. Lewis, Ernie Kuyt, Kenneth E. Schwindt, Thomas V. Stehn

Proceedings of the North American Crane Workshop

A total of 1,893 whooping cranes (Grus americana) overwintered at Aransas National Wildlife Refuge from 1950 through spring 1987. Winter losses (dead and disappeared) amounted to only 1.3% of the population, but 3.7% of the juveniles. About 19% of the annual losses occurred in the wintering area where birds spend 5 to 6 months of the year. Eighty-one percent of the losses occurred from April to November. Losses on the summering area appear to be low. The most significant losses seem to occur during migration and may comprise between 60 and 80% of the annual losses. Migration involves …