Monitoring migratory raptors in Manitoba’s Pembina Valley

Bald Eagles were recorded in record numbers for Manitoba

A Rocha Canada’s new field study centre, located in the Pembina Valley, provides an important opportunity to document the valley’s biodiversity. The Valley is on a key raptor migration corridor. The Pembina Valley raptor migration project is A Rocha Pembina Valley’s (ARPV) first step toward this goal and is also Manitoba’s first standardised annual spring raptor migration count.

The Pembina Valley, located 125 km south-west of Winnipeg, is a mosaic of deciduous woodlands, pastures and croplands. Each spring, thousands of raptors migrate northwards into Manitoba, Canada’s central province, en route to their summer destinations. Some of these birds of prey find their way through the valley. Migrating raptors were counted during late winter and early spring of 2005 and 2006. Two primary observers were present on nearly all count days. Observers tried to arrive prior to the daily start of migrating raptors and stayed until a half hour after what was assumed to be the last raptor of the day. Birdwatchers and visitors to the site aided in spotting raptors. Weather information was recorded on-site and also accessed from three weather stations within 55 km of the count site. In addition to the count, a Raptor Awareness Day was held in both years in the nearby town of Morden.

Raptor counters in the Pembina Valley

In 2005 and 2006, raptor counters identified a total of 15 migratory raptor species in the Pembina Valley with a total count of 17,580 birds. Counts over the two years were made on 68 days resulting in 490 hours of observation. Red-tailed Hawks Buteo jamaicensis, Bald Eagles Haliaeetus leucocephalus and Sharp-shinned Hawks Accipter striatus were the most common species seen. In 2006, Manitoba’s one-day record count of Bald Eagles was broken twice, with 174 individuals seen on one day and 245 on another. The most abundant species was the Red-tailed Hawk which numbered 6546 individuals in 2005 and 7107 in 2006. Raptor numbers peaked daily between 13:00 and 15:00 hrs. Most migrating raptors (9576) were associated with winds from the south-east quadrant.

The Pembina Valley count site ranks as the highest spring raptor count in western North America and rivals the top spring North American site for migrating Red-tailed Hawks. Long-term monitoring data will give conservation organisations a better understanding of the Pembina Valley’s importance to raptors and will contribute towards assessing Manitoba’s raptor migration status and trends. A portion of this migration corridor in the Pembina Valley has been recommended as an Important Bird Area.

Project leader: J. Paul Goossen

Partners: Manitoba Important Bird Areas Program, Pembina Valley Conservation District, Pembina Valley Development Corporation, Town of Morden. Donors: Allmar Industries, Bill and Margaret Fast Family Foundation, M. Goossen, P. and V. Goossen, R. Goossen and I. and I. Pauls