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Trumpeter Swan

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The Kenai National Wildlife Refuge supports an expanding Trumpeter Swan population on more than 4,600 lakes. This is particularly good news given that of all the North American subpopulations sampled by Oyler-McCance et al. (2006), the swans collected on the Kenai Refuge had the highest level of allelic richness (i.e., genetic diversity).

Little was known about trumpeter swans in 1957 when the first aerial Trumpeter Swan survey was initiated by Dave Spencer on the Kenai Peninsula. Shortly thereafter, Will Troyer expanded field work during 1964-1968 to include studies of territoriality, molting, preflight brood movements, and other behavioral characteristics (Hansen et al. 1971). The Kenai Peninsula was included in the first comprehensive statewide survey of Trumpeter Swans in 1968 when U.S. Fish and Wildlife Service personnel counted 2,848 Trumpeter Swans (Hansen et al. 1971). Ted Bailey and colleagues subsequently used neck collars and radio transmitters to study the summer and migratory movements of adult swans and cygnets on Kenai Refuge during 1982-1985 (Bailey et al. 1988).

From 1957 through 1984, the known breeding population on KENWR remained ~30 pairs despite a 2-fold increase in swan numbers throughout the rest of Alaska (Bailey et al. 1986).  At that time, it was speculated that nesting sites in optimum habitat were saturated on KENWR (Richey 1981, Bailey 1984).  Our 1985 Comprehensive Conservation Plan (CCP) recognized that populations of Trumpeter Swans were depressed, apparently due to human activities.  To help ameliorate human disturbance, the 1985 CCP prohibited aircraft landings on lakes used by nesting trumpeter swans and/or their broods from 1 May through 30 September; this regulation also resulted in the removal of several aircraft taxi-operator and boat-equipped tent camps on refuge lakes.  Additionally, motorized boats were also restricted on part of the Kenai River below Skilak Lake used by spring-staging swans. The breeding population increased rapidly and steadily after aircraft regulations were put into place, with more than 50 pairs currently nesting on the Kenai Refuge.  However, declining mean brood size over this same time interval also suggests that optimum breeding habitat may be saturated. 

Despite these successes within Kenai National Wildlife Refuge, human disturbance on lakes outside refuge boundaries may be hindering the establishment of new pairs elsewhere on the Kenai Peninsula.  The number of nesting pairs has only increased on lakes within Kenai Refuge (despite decreased habitat availability due to refuge boundary adjustments and land exchanges) and not on lakes outside refuge boundaries. Nesting and  brood rearing habitats in Kenai Refuge, particularly on closed-basin lakes, is likely to continue declining in the future because of increased water body evaporation due to a warming climate (> 60% of recently sampled water bodies experienced some level of drying).  Other management issues with potential to affect trumpeter swans on the Refuge include renewed public interest in aircraft access, increasing levels of recreational use, and low beaver populations. Consequently, the 2010 CCP maintains these restrictions, but the previous closure date will be modified to 10 September to be consistent with other aircraft regulations. 

Bailey, T.N.  1984.  Terrestrial habitats and wildlife species.  Technical supplement to the Kenai Comprehensive Conservation Plan.   U.S. Fish and Wildlife Service, Anchorage, AK.  72+pp.

Bailey, T.N., E.E. Bangs, and M.F. Portner.  1986.  Trumpeter Swan surveys and studies on the Kenai National Wildlife Refuge and Kenai Peninsula, Alaska, 1957-1984.  Pages 64-66 in D. Compton (ed.).  Proceedings and papers of the 9th Trumpeter Swan Society Conference, West Yellowstone, MT.  132 pp.

Bailey, T.N., M.F. Portner, E.E. Banks, W. W. Larned, R. A. Richey, and R.L.Delaney.  1988.  Summer and migratory movements of Trumpeter Swans using the Kenai National Wildlife Refuge, Alaska.  Pages 72-81 in D. Compton (ed.).  Proceedings and Papers of the 11th Trumpeter Swan Society Conference, Everett, WA.  178 pp.

Hansen, H.A., P.E. K. Shepherd, J.G. King, and W. A. Troyer.  1971.  The Trumpeter Swan in Alaska.  Wildlife Monographs, No. 26, 83pp.

Oyler-McCance, S.J.,  F.A. Ransler, L.K. Berkman, and T.W. Quinn.  2006.  Comparison of Trumpeter Swan Populations using Nuclear and Mitochondrial Genetic Markers.  Final report.  Prepared by Rocky Mountain Center for Conservation Genetic and Systematics, University of Denver, CO, and US Geological Survey, Fort Collins Science Center, CO, for USFWS Migratory Birds.  51 pp.

Richey, R.A.  1981.  Status of the Trumpeter Swan on the Kenai National Wildlife Refuge.  Pages 20-21 in D.K. Weaver (ed.).  Proceedings and Papers of the 6th Trumpeter Swan Society Conference.

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Last Updated: Mar 18, 2014
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