Loon Study - Update

Scientists with the U.S. Geological Survey and the Wisconsin Department of Natural Resources are evaluating a new way of monitoring movements and behavior of common loons. Miniature archival geolocator tags were attached to 18 adult common loons in northern Wisconsin this past summer. The tags are attached to a leg band on the loon, where they measure and record light levels, temperature, and pressure for up to two years. Daily location (latitude and longitude) can be determined from sunlight levels, dive information from pressure measurements, and activities such as flight or incubation patterns can be interpreted from temperature data. The tags are a little over half the size and a third the weight of an ‘AAA’ battery. The tagged loon must be recaptured to obtain the tag and download the data. The chance of recapturing a nesting common loon in Wisconsin is about 90%, so it is highly likely that the tags will be recovered after being attached to the bird for a year or two.

This technology is of interest as an alternative to satellite telemetry for obtaining migration information. The location information is not as accurate as satellite telemetry, but the small size of the tag lends itself to a less invasive leg band attachment and the archival tags are about 1/3 the cost of a satellite transmitter. Geolocator tags have been successfully used to document the migration patterns of a number of sea bird species. It appears that geolocator tags will work well with common loons as well. We have not observed any harmful effects on loons fitted with the tags thus far. This summer we noted the behaviors of 10 loons that were tagged in early May, and normal nesting activities were confirmed in eight of the birds.

For more information, contact:
Kevin Kenow, U.S. Geological Survey
Upper Midwest Environmental Sciences Center
2630 Fanta Reed Road, La Crosse, Wisconsin
Phone: 608.781.6278
Email: kkenow@usgs.gov