Saw-whet Owl Migration Monitoring at
Thunder Cape Bird Observatory

1999 Results • Banded Owls Netted at Thunder Cape

---

From Thunder Cape News, February 1998.

In the first three fall seasons of Thunder Cape Bird Observatory's operation (1991 - 1993), owl banding took place on a casual basis and met with considerable success. During this period 219 Northern Saw-whet Owls were banded.

In the fall of 1994, the observatory undertook the task of monitoring Northern Saw-whet Owl migration at Thunder Cape in a more intensive manner than previous years. This was to be done through netting and banding for a fixed period each night during a period consistent with the migration window for saw-whets, mid September through late October. Lure tapes of a calling saw-whet have proven very successful at other banding stations, and TCBO also opted for this method.

Over the years, there have been several changes in methodology, including net locations, mesh size of nets and net height. However, these changes have been done in a way as not to compromise or invalidate previous years' data.

Since 1994, a total of 1273 saw-whets have been banded. Results have been very encouraging but more years of data are needed for trend analyses to be meaningful. Since 1991, 37 of "our" birds have been recovered in other locations. Over half of these were recovered in the same fall migration (Table 1). It should be noted that distances listed are straight line. An impressive 18 foreign recoveries or "controls", birds that were banded elsewhere, have been captured. We have also had a number of birds returning from previous years.

Most recoveries are from established banding stations located along the shores of the western Great Lakes, Superior, Michigan and Huron. However, Steven's Point, located in central Wisconsin, has been a site of several recoveries.

On the night of October 2nd, 1995, 53 saw-whets were banded at TCBO. Within 15 nights of banding, three birds traveled a combined distance of nearly 1050 km to reach Hawk Ridge, Steven's Point, and Whitefish Point. The three birds traveled an average of 27, 28, and 30 km per night to reach their respective recovery locations. Three possible travel routes from Thunder Cape become evident from the map in Figure 1.

Figure 1.

Following the shoreline southwest from Thunder Cape seems to be the overwhelmingly preferred route by saw-whets. Based on recovery information, it takes an average of 2 weeks to reach Hawk Ridge in Minnesota (average speed of 19 km per night), although one speedster made it in 6 nights or less, averaging 45 km per night.

Once around the western tip of Lake Superior, some owls may head east into Wisconsin. Circumventing Lake Superior, it is about 620 km to Steven's Point from Thunder Cape. Birds would have to travel an average of 40 km per night according to the recovery information.

Another, possible route from Thunder Cape into Wisconsin, is flying south, over Lake Superior. It takes on average 15 nights to reach Steven's Point. The fastest travelling time from recovery information is ten nights or less. If this individual followed the north shore down to Duluth and then went southeast to Steven's Point, it would have had to fly an average of 62 km per night. Crossing Lake Superior it would have averaged 42 km per night. This is remarkably consistent with the minimum time to reach Hawk Ridge.

This route would also explain the same-season recovery from Cedar Grove, on the western shore of Lake Michigan. It took 25 nights to travel 540 km, an average of 22 km per night. Assuming birds would island hop from Thunder Cape south to Isle Royale, Michigan, the closest distance to mainland on the south shore is about 70 km away.

It appears only a minority of birds head east from Thunder Cape. There is one fall recovery from Whitefish Point, Michigan, located on the southeast shore of Lake Superior. All three spring recoveries are from east of Thunder Cape, one in Northwestern Ontario, and two in the lower peninsula of Michigan.

Cooperation with other banding stations and sharing of recovery information would provide more insight and increase the general understanding of migratory patterns of owls in the Great Lakes area.

Owl migration monitoring has become an integral part of TCBO activities. This has only been possible through the dedication of TCBO volunteers who worked very hard, sometimes working exceedingly long hours, doing a "double-shift". Playing a small part in gaining a knowledge that may help conserve the species, has been their sole reward (apart from the immediate gratification of handling a soft, toy-like creature).

How you can help

Thunder Cape Bird Observatory is offering certificates of adoption for
Saw-whet Owls, as well as Sharp-shinned Hawks and Magnolia Warblers.
See our Gift Shop for more information.

---

Back to TCBO PAGE • Back to BIRDING PAGE