WESTERN GREAT LAKES REGION OWL SURVEY: 2010 Report

Grosshuesch, David; Brady, Ryan

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 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 sixth 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), Wisconsin Bird Conservation Initiative (WBCI), 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 2010, surveys were conducted between April 1 and April 15. All survey routes were randomly chosen and consisted of 10 survey points spaced ~1.6 km (1 mile) apart. There was a 5 minute passive listening period at each designated survey point along the route. This will provide data for testing detection probabilities using removal sampling, which should improve population estimates and provide a more effective evaluation of management decisions. The number of routes assigned in 2010 was 204, with 118 in Minnesota and 86 in Wisconsin. Of the assigned routes, 99 and 76 routes were surveyed in Minnesota and Wisconsin, respectively. The number of participants that signed up to conduct an owl survey was 168, with 135 volunteers (80%) returning completed survey sheets. In total, 313 owls of eight species were recorded on 108 routes, with no owls recorded on 67 routes (Table 2). The top three owl species combined for Minnesota and Wisconsin were Barred Owl, Northern Saw-whet Owl, and Great Horned Owl, respectively. In Minnesota, a total of 164 individual owls comprising seven species were recorded. The mean number of owls/route was 1.64 compared to 1.18 in 2009. In Wisconsin, a total of 149 individual owls comprising six species were recorded. The mean number of owls/route was 1.96 compared to 1.77 in 2009. Recommendations and future perspectives for the Western Great Lakes Region owl survey include: 1) centralize storage of all data collected to date into the newly-created Midwest Avian Data Center, 2) develop an on-line data entry system, 3) conduct analysis of owl habitat associations, detectability, climatic variables influencing owl calling activity, and power of the current survey to detect population trends, and 4) assess the need to use playback to increase detections for species of interest (i.e., Boreal Owl, Great Gray Owl, Long-eared Owl, Short-eared Owl)

WESTERN GREAT LAKES REGION OWL SURVEY: 2010 Report

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