Background

Every five years since 1985, LoonWatch has conducted a one-day loon survey on a randomly chosen group of lakes to estimate the size and distribution of Wisconsin's Common Loon population. Volunteer observers visit a lake or lakes on one day in July between 5:00 AM and 10:00 AM to count both adults and chicks. This information is then used to estimate the number of breeding adults and the number of chicks produced. Over time, the survey tells us the trend in the state's loon population - whether it is stable, increasing or declining.

The 2005 Population Survey was the Best Yet!

On July 16, 2005 LoonWatch conducted the 5th statewide loon population survey. Paul Rasmussen with Wisconsin DNR conducted the analysis to determine if there has been a significant change in Wisconsin’s loon population in the last 5 years.

The results indicate that the outlook for Wisconsin’s loon population looks good. The adult loon population for 2005 was estimated at 3373 (± 495) and chick population was estimated at 805 (±218). This represents a marginal adult population increase over 3131 adults estimated in 2000 and significant chick population increase over 462 in 2000.  Thus 2005 had the largest loon population estimate since the survey started in 1985.

We also look at what proportion of the loon population comes from four lake size classes. When the two smaller lake classes (25-149 ac) were combined and the two larger lake classes (150+ ac) were combined, an interesting pattern emerges over time. In 1985, 20% of the population was found on the large lakes and 80% on the small lakes. As of 2005, this ratio was about equal with approximately half of the population on small lakes and half on large lakes. We don’t collect any other data with this survey to correlate our population numbers to lake factors that may be the cause for this shift. We can speculate that something has changed on small lakes that make them last attractive to loons or something has changed on the large lakes that make them more attractive than in the past. One is left wondering if a shift toward increased shoreline development on small lakes over the past 20 years might not be at least part of the cause. Regardless, our loon population seems to be adapting to these changes as the population seems to be doing well.

The 6th Wisconsin Loon Population Survey will be conducted in July of 2010. If you live on or visit a lake regularly and want to get involved in loon monitoring before then, please check out LoonWatch’s Annual Loon Monitoring Program.

Summary of Results from 2000

During the 2000 survey, volunteers observed 223 adults and 34 chicks on 151 lakes in 25 counties. Using these data, the 2000 Wisconsin loon population was estimated at 3,131 adults and 462 chicks. The 2000 adult population estimate was significantly larger than the 1985 estimate of 2,358. The chick population estimate was the lowest on record but did not differ significantly from any of the previous surveys. The adult Common Loon population in Wisconsin appears to be strong and may even be growing. Though it would be inaccurate to view the 2000 survey data as a sign that loon productivity in Wisconsin is declining overall, it is important to note that moderate to large lakes are an important component of the loon's breeding habitat, and research by the Wisconsin DNR has found that these areas are under the greatest pressure from development and recreational use.

Excerpts of survey results from: Gostomski, Theodore J. and Paul W. Rasmussen. 2001. Results of the 2000 Common Loon Survey in Wisconsin. Passenger Pigeon. 63(1&2): 15-25.