We recently completed the tenth year of our long-term population study of Seattle’s urban-nesting Cooper’s Hawks. This study builds on the 2003-2011 pioneering work of Jack Bettesworth.
Our study has three main goals. First, we census within the 84-square-mile city limits of Seattle to try to count all the Cooper’s Hawk nests (a nearly hopeless task). This year we found 69 pairs engaged in courtship and nest building. Eight pairs failed during nest building. 61 pairs went on to incubate eggs. Four sites failed during incubation (one from nest collapse, the others from unknown causes). Fifty-seven sites hatched, and five failed after hatch. Despite the record high failures, a record high of 52 pairs produced fledged young; the previous record was 51 pairs in 2020.
Second, we count the number of young fledged from each nest. We documented another record: 192 young lived long enough to fledge, a great productivity of 3.7 young per successful nest.
Third, put unique color-ID bands on as many birds as possible to track individual birds as they move around (females: orange band, right leg; males: purple band, left leg). Each band has a unique alphanumeric code (e.g., purple S over 5). This season we banded 58 youngsters and 14 adults. Since 2012, we have banded 417 birds, with 480 subsequent sightings on 182 different birds, a return rate of 43%. The vast majority of sightings are year-round in Seattle (407) or non-Seattle parts of King County (37), indicating a largely non-migratory population.
As in the past, the 69 pairs of nest-building Coops in 2021 picked a diverse list of nest tree species. Perennial favorites were well-represented: Big Leaf Maple (21), Douglas Fir (15), Madrona (6), White Pine (9), and Alder (2). Two new species, Hawthorn and Tulip, were added. We found a total of 82 nests (13 pairs built two nests). Most nest sites are in Seattle parks and greenbelts (50), followed by private property (14), cemeteries (3), U.S. government (1), and University of Washington (1).
These 69 nest-building pairs in Seattle (a known nesting density of one pair for every 1.2 square miles) are the MINIMUM number in the city. Some potential nesting areas are nearly impossible to search because of terrain and safety concerns (e.g., the steep, trail-less, overgrown greenbelt along the railroad north and south of Golden Gardens; parts of the extensive West Duwamish Greenbelt; encampments on the wooded hillside of Beacon Hill along I-5).
The brutal triple-digit temperatures in June occurred while young of many raptors and other species were still in the nest. This led to nest failures, mortalities and many rescues, as described in our Summer 2021 newsletter (https://urbanraptorconservancy.org/summer-2021/).
After young had fledged and dispersed, volunteer banders responded to six calls for help trapping wayward birds out of warehouses and parking garages.
We owe special thanks to our team of volunteers and the many individuals who shared reports with us. This work would be even more impossible without their dedication.
We produce an annual report that is archived on our website. You can receive this and 3-5 other reports each year by signing up for URC Updates on our website. We do not share our mailing list, period.
We greatly appreciate any color ID band readings from Tweeterdom!