Eagle Roost Count Results From the Ferry Bluff Eagle Council 1-10-2012

Posted by gengberg on January 10th, 2012

Roost Count Results
Sunday, 8 January. 2012

Hello all of you fine counters: Both the weather and our count of 45 eagles today was quite different from the last count conducted on December 18, 2011 when 176 eagles were tallied. The decline in birds in our area is likely due to the birds being highly dispersed along the Wisconsin River, and an even broader area. The lack of ice on rivers and lakes, as well as the lack of snow cover means that carrion and fish are widely available to birds, and the birds respond by spreading out considerably. It appears that eagles only congregate when food abundance requires them to gather. Otherwise, these territorial individuals seem to like their space. Eagles, for example, were reported this week as common along the Wisconsin River, in agricultural fields located within 5 miles of the Wisconsin River, and around the Madison lakes. Another measure of lack of ice and broad distribution of eagles comes from the annual mid-winter aerial survey of the Wisconsin River that the Wisconsin Department of Natural Resources conducts. This year’s count occurred on January 4, 2012 and surveyed the Wisconsin River from the Pettenwell Dam downstream to the confluence with the Mississippi River. Except for near Pettenwell and on Lake Wisconsin (upstream of the dam at Prairie du Sac), little ice cover was seen along the Wisconsin River during the survey. Upstream of our survey area, the WDNR counted 41 eagles from the Petenwell Dam downstream to the stretch of river that passes under the I-39 bridge. Within our counting area, WDNR biologists counted 77 eagles between the I-39 bridge and the point where Highway 130 crosses the Wisconsin River near Lone Rock. This stretch of river approximates our counting area except for the 14 eagles that we counted off river at Leland and at Ederer/Been Roosts. Another 68 eagles were located on the WDNR survey downstream of Highway 130 to the junction with the Mississippi River. On January 4, eagles were thus spread relatively evenly along the Wisconsin River, much as we found in our count today, but on a broader scale. Our roost numbers from roosts located near the Wisconsin River totaled 31 birds, less than half seen on a comparable stretch of river covered by the aerial survey.Between January 4 and today, the weather has been extremely mild, so it is possible that eagles have spread out even more since the aerial survey was conducted. From our past eagle research, warm periods induced telemetered eagles to move further north to distant places such as the Chippewa River and Stevens Point. These shifts appear to be the normal response to changing winter conditions by eagles, and to a tendency by these territorial birds to winter as close to their summer breeding territories as winter conditions allow.Unfortunately, colder winter conditions are not expected until this Thursday, so the abundance of eagles, as they appear to people coming to watch eagles this next weekend, will appear very low unless we get a substantial snowfall soon. That said, winter conditions can change rapidly, and the mobile eagle will change its distribution just as rapidly.Collectively you all applied 36 hours of counting effort this weekend, and your efforts are much appreciated!