22 March 2001 

A nesting pair of Canada geese in an Anchorage wetland

ANCHORAGE GOOSE STUDY UNDERWAY 

Biologists with the U.S. Geological Survey’s, Alaska Science Center - Biological Science Office surgically implanted radio transmitters in 100 Anchorage Canada geese during the summer of 2000 and plan to do the same this summer.  The study was designed to measure the effects of surgically-implanted radios on geese.  Biologists are also gathering data on movements of geese within the Anchorage Bowl.  That information may help local wildlife managers assess how often birds move into areas where they are in conflict with humans. 

Surgically implanted radio transmitters have been used in Alaskan waterfowl over the past seven years to study migration and determine locations of wintering areas.  The technique was developed because some birds do not tolerate radio transmitters that are attached to the outside of the body.  Discoveries resulting from surgically implanted radios have contributed to efforts to conserve wild populations.  Biologists used surgically-implanted transmitters to locate the Bering Sea wintering area of spectacled eiders, a threatened species that nests in western and northern Alaska.  Surgically implanted radios transmitters have also been used by USGS to study the lingering effects of the Exxon Valdez oil spill on harlequin ducks in Prince William Sound, response of white-fronted geese to aircraft disturbance, and migration of emperor geese from the Yukon Delta to their wintering areas on the Alaska Peninsula and Aleutian Islands. 

Canada goose with a radio implant

USGS plans to use surgically implanted radios to study the spring migration of geese and their nesting efforts on breeding grounds.  However, before doing so biologists need to verify that the radios do not influence behavior and nesting by geese.  The advantage of using Anchorage geese in this study is that the birds are more easily observed than in wild populations. The Anchorage population of geese is also quite healthy making capture and marking of an adequate number of birds possible.

Surgeries are conducted by a USGS veterinarian with over seven years of experience in implantation of radio transmitters. There were no mortalities during surgeries last year and birds recovered quickly.  Following surgery, the flexible antenna that protrudes above the bird’s tail is the only part of the transmitter that is visible. In addition to geese that received surgically-implanted transmitters, biologists also put colored plastic leg bands on an additional 69 birds that served as a control group. They then monitored behaviors of the two groups and found that surgical implantation of radios caused no change in the behaviors of birds.  However,  long term effects on reproduction have yet to be determined.  Therefore, this spring biologists will locate nests of females to determine whether nesting by females with radios is similar to females without radios. Biologists will also compare survival of the two groups over the next three years. 

This project is not part of ongoing efforts by state and federal agencies to reduce the population of Anchorage Canada geese. However, information collected during the study will improve understanding of the local population and may help wildlife managers reduce conflicts between geese and people. 

Study Results  We conducted 83 paired observations of Small Transmitter and Control females (40.33 hours) and 86 paired observations of Large Transmitter and Control Group females (41.50 hours).  There were no significant differences in behaviors of Small Transmitter and Control females (F = 0.32; 5, 73 df; P = 0.9023) or Large Transmitter and Control birds (F = 0.23; 5, 76 df; P = 0.9470).  We therefore combined both radio transmitter treatments and found no differences in their behaviors when compared to the Control females (F = 0.26; 5, 159 df; P = 0.9334).  There was no interaction between treatments and time since surgery (F = 0.61; 25, 592.16 df; P = 0.9338).  The 5 behaviors of interest made up 85-95% of the total time budget for all geese.    Between 18 October and 25 October 2000, 93% (n=165) of our marked Canada geese departed Anchorage on their fall migration.   Birds in different treatment groups departed at similar dates.  Conclusion We conclude that abdominally-implanted radio transmitters did not significantly alter the behaviors of adult female Canada geese during the period between molt and departure for fall migration.  Females recovered from surgery quickly and showed no unusual behaviors in the first 10 days after radio implantation.  Female geese rarely acknowledged the external whip antenna and exhibited no increase in preening around the area of incision.  In future field seasons we will test whether surgically-implanted radio transmitters affect reproductive efforts or survival of geese.

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