WESTERN GREAT LAKES REGION OWL MONITORING SURVEY 2007 Final Report

Grosshuesch, David

As top predators of the food chain, owls are considered good indicators of environmental health, making them important to monitor. However, there is a paucity of abundance and population status data available for most species of owls in the western Great Lakes region. Currently, few species of owls are adequately monitored using traditional avian survey methods, such as the Breeding Bird Survey (BBS) and Christmas Bird Counts (CBC). For these reasons, the Western Great Lakes Region Owl Monitoring survey was initiated in 2005. The objectives of this survey are to: 1) understand the distribution and abundance of owl species in the region, 2) determine trends in the relative abundance of owls in the region, 3) determine if trends are comparable in surrounding areas and analyze whether these trends could be scaled up or down on the landscape, and 4) determine if there are habitat associations of owl species in the region. This was the third year of a collaborative effort between personnel from the Hawk Ridge Bird Observatory (HRBO), Natural Resources Research Institute (NRRI), MN-Dept. of Nat. Res. (MN-DNR), and the WI-Dept. of Nat. Res. (WI-DNR) to monitor owl populations in the western Great Lakes region. Existing survey routes were used to conduct roadside surveys in Minnesota and Wisconsin. In 2007, the survey effort was expanded throughout the remainder of Minnesota, with routes available in southern and western Minnesota. Volunteers were requested to conduct a survey in each period (Period 1-March 10 to March 18; Period 2-March 19 to April 8; Period 3-April 9 to April 22). All survey routes consisted of 10 survey points spaced ~1.6 km (1 mile) apart. A 2 minute “passive” listening period was done at each designated survey point along the route. The number of routes assigned in 2007 was 185, with 108 in Minnesota and 77 in Wisconsin. Of the 185 assigned routes, 80 and 60 routes were surveyed in Minnesota and Wisconsin, respectively. At least two surveys were conducted for 124 of the 140 routes completed, with 83 routes being surveyed three times. The number of participants that signed up to conduct an owl survey was 153, with 116 volunteers returning completed survey sheets. In total, 536 owls of seven species were recorded on 107 routes, with no owls recorded on 33 routes (Table 2). The top three owl species combined for Minnesota and Wisconsin were Barred Owl, Great Horned Owl, and Northern Saw-whet Owl, respectively. In Minnesota, a total of 230 individual owls comprising seven species was recorded during all survey periods. The mean number of owls/route was 1.00 for Period 1, 1.08 for Period 2, and 1.37 for Period 3. In Wisconsin, a total of 306 individual owls comprising 5 species was recorded during all survey periods. The mean number of owls/route was 2.00 for Period 1, 2.06 for Period 2, and 2.11 for Period 3. Recommendations and future perspectives for the Western Great Lakes Region owl survey include: 1) provide on-line training and certification to volunteers, 2) possible integration of an on-line data entry system, 3) completing the analysis of seasonal calling activity data, 4) conducting future analysis on abundance trends, habitat associations, and distribution, and 5) considering the importance of using and collecting small mammal data.