Annual and seasonal survival of trumpeter swans in the upper midwest

The reintroduction of trumpeter swans to the north central United States appears to be a conservation success story. For the most part, population management goals have been met or exceeded. The population cannot be considered self-sustaining, however, because 90% of the swans migrate short distance...

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Bibliographic Details
Published in:The Journal of wildlife management 2012-01, Vol.76 (1), p.129-135
Main Authors: Varner, Dana M., Eichholz, Michael W.
Format: Article
Language:English
Subjects:
annual survival
Bird migration
Cygnus buccinator
Geese
Habitats
Ice
migration
Mortality
Natural resources
Population Ecology
reintroduced species
Seasonal migration
seasonal survival
Species reintroduction
Summer
Swans
trumpeter swan
Waterfowl
Wildfowl
Wildlife ecology
Wildlife management
Wildlife sanctuaries
Winter
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Summary:The reintroduction of trumpeter swans to the north central United States appears to be a conservation success story. For the most part, population management goals have been met or exceeded. The population cannot be considered self-sustaining, however, because 90% of the swans migrate short distances to wintering sites where supplemental feeding occurs. The remaining 10% migrate longer distances to areas where adequate open water and forage occur naturally. To determine how these 2 different wintering habits might affect mortality, we used mark-resight data gathered between 2000 and 2008 to estimate and compare annual survival rates for long-and short-distance migrant swans marked in Wisconsin. Apparent annual survival rates were similar for long-(0.81, SE = 0.019) and short-(0.81, SE = 0.022) distant adult migrants but were higher for long-distance sub-adult (0.86, SE = 0.036) migrants than for short-distance sub-adult migrants (0.7, SE = 0.046). We also estimated seasonal survival of long-distance migrants to determine if the migratory periods are a time of high mortality. We found little evidence for seasonal variation in survival and estimates for both migratory and non-migratory seasons were very high (> 0.97). Overall, the results suggest that little mortality occurs during migration and long-distance migrants are able to survive at rates at least equal to, but probably higher than, short-distance migrants.
ISSN:0022-541X
1937-2817
DOI:10.1002/jwmg.280