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G&F Requests Reports of Trumpeter Swan Mortalities

Late winter can be a tough time for swans. G&F seeks reports of any dead swans.

3/23/2017 2:25:07 PM

Jackson - Late winter can be a harsh time for trumpeter swans and the Wyoming Game and Fish Department (WGFD) is asking for reports of dead swans. The largest number of swan mortalities occurs in March, especially of cygnets, or young hatched the previous year. Limited wetland food resources that have been available during winter are now mostly depleted. Swans lose up to 20% of their body weight during the winter months, especially during harsh winters, which can leave them in a much weakened state. As soon as temperatures begin to rise, swans can be seen moving about the landscape, seeking out newly opened water for foraging sites. Swans face a number of challenges during this time, including collisions with power lines, fences and bridges, emaciation from parasite loads or disease, and predation.
 
Migrant birds from Canada, which make up over 90% of the trumpeter swans that winter in the Greater Yellowstone, will start to depart for the north and most are gone by the end of March.   They spend time at lower elevation wetlands in Montana before continuing on their journey to nest sites farther north in Alberta and the Northwest Territories. The resident swans that remain year-round in Wyoming, however, need to subsist on local resources and wait for nest ponds to open. In years when the spring thaw is delayed and winter conditions persist, wetland nest sites may not open up until late May or June and few pairs will produce young. 
 
Recently, the Wyoming Game and Fish Department heard from a few concerned citizens that a young trumpeter swan appeared to be stranded along the bike pathway near Melody Ranch.  Game and Fish Nongame Biologist Susan Patla responded and found the swan trapped between snow piles near homes off South Park loop road. Helpful neighbors assisted Susan in securing the swan. The swan appeared to have no injuries and was not emaciated, so Susan released it to nearby Flat Creek where it immediately walked into the creek and began drinking water and eating aquatic vegetation. Other swans are not as fortunate.  Jackson Game Warden Kyle Lash found a dead swan near the Jackson library the week before, apparently having hit a power line along Snow King Blvd. Another cygnet, that hit a power line and then was partially scavenged, was found along Fish Creek Road.  Wyoming Game and Fish biologists ask that any swan mortalities be reported to regional offices. If carcasses are intact and fresh, the State Wildlife lab can complete necropsies to determine the cause of disease such as disease, parasites or heavy metal concentrations which may be directly or indirectly involved.  Any questions should be directed to Susan Patla, Jackson Regional Office, telephone 307-733-2383  ext. 229.
 
The restoration of the trumpeter swan nesting population has been a major success story in Wyoming. Work by WGFD and many other partners since the late 1980s has resulted in an increase in population from an average of 60 swans to 236 adults/subadults counted in 2016.  This success is a result of the Department’s Green River range expansion project as the number of swans in the Jackson area/Snake River drainage has remained the same since the 1980s.  Working with Wyoming Wetlands Society, WGFD released a total of 75 captive-raised swans from 1994-2002 in the Pinedale area. Since the mid-2000s, swan numbers and distribution have continued to increase as wild pairs pioneer new nest sites in the Green River basin. In 2016, a pair produced young in the town of Green River, which makes it the farthest southern nesting swan ever documented in Wyoming. Overall, the expansion of swans into new summer and winter habitat, such as open water on the Green River below Fontenelle Dam, has greatly increased the probability that swans will persist for future generations of Wyoming citizens and visitors to enjoy.  

(Mark Gocke, Regional Info & Education Specialist)

- WGFD -

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