WA - Trumpeter Swan Lead Shot Poisoning Investigation in Northwest Washington and Southwest British Columbia : FINAL REPORT
1F40, DEC# 200310003
1 - 60
PUBLICATION DATE: June 2009
In 2001, an international effort was initiated to locate the source(s) of the lead. Participants in the investigation include the Washington Department of Fish and Wildlife, U. S. Fish and Wildlife Service, Environment Canada – Canadian Wildlife Service, The Trumpeter Swan Society and the University of Washington (Washington Cooperative Fish and Wildlife Research Unit) with assistance from numerous other government and non-government organizations. The partners took a multi-faceted approach to investigate the swan die-off and potential secondary exposures to other wildlife, including bald eagles.
Wintering swans were captured and blood samples were collected and analyzed for blood lead content. Trumpeter swans were fitted with VHF or satellite transmitters attached to a coded neck collar and tundra swans were fitted with a coded neck collar. Telemetry surveys were conducted each day and night during the winter to document locations of marked individuals. Swan population surveys were conducted to obtain additional detail on population movements and to validate the telemetry data. Sick and dead swans were collected throughout the winter, and carcasses examined to determine cause of death, measure liver lead residues, and recover shot from gizzards.
The locations of collared swans were used to identify forage areas and roost sites, and data for swans that died from lead poisoning after radio-collaring were used to identify and prioritize areas for lead shot density assessment (shot collected from soil/sediment sampling). Lead shot density assessments recovered shot in most crop fields and water bodies sampled. Relatively high densities of lead shot were found on the U.S. side of Judson Lake (a ~100 acre lake spanning U.S./Canada border).
An adaptive management approach was undertaken to determine the extent to which Judson Lake was a contributing source of lead shot causing swan mortalities. Swans were precluded from using Judson Lake for two winters (2006-2007 and 2007-2008) by both passive (windsocks, effigies) and active (noise makers, laser light, airboat) deterrent methods. The number of lead poisoned swans in the study area decreased by at least 50% for each of both years compared to the average of the 5 previous years.
State and Federal Law Enforcement Agents increased waterfowl hunter compliance checks in the area during the 2001 and 2002 waterfowl hunting seasons. Compliance for non-toxic waterfowl loads was reported to be exceptionally good in the area. Environment Canada’s Enforcement Officers conducted hunter compliance checks each year of the investigation; very good compliance was reported.
By extrapolating historic growth rates to the present time or by using a simple demographic model, approximately 4,000 (actual and potential) trumpeter swans were estimated to have been lost from the Pacific population from 1999 to 2006. This equates to ~14% loss from the potential 2005 Pacific breeding population and ~23% loss from the potential 2006 SW-B.C. & NW-WA winter population. Despite these losses, both populations are increasing.
A notice was issued to U.S. and Canadian wildlife rehabilitators, State/Provincial veterinarians and biologists, and Federal Law Enforcement agents to request analyses of all bald eagles submitted from northwest Washington for lead exposure through the winter months. From the 1999-2000 winter through the 2006-2007 winter, a total of 62 eagle liver samples from the U.S. side of the border were analyzed for lead residues. Two of the eagles had elevated subclinical lead exposures and ten had lethal lead exposure levels. From 1999-2008, a total of 19 bald eagles from the Canadian side of the border were analyzed for lead residues; 2 of the eagles had lethal lead exposure levels.
In order to provide the general public with information on the project and the status of the swan mortality events, the partners cooperatively developed talking points and media contacts, released annual progress reports, provided information on a USFWS web site, and provided opportunities to attend an annual stakeholders meeting. In addition, two public information sessions were held (one in Whatcom County, Washington and the other in Abbotsford, British Columbia). Two posters promoting the use of non-toxic shot were produced and distributed by Environment Canada-Canadian Wildlife Service (EC-CWS).