URC Update | December 2024
2024 Seattle Cooper’s Hawk Project: Annual Report
Every Cooper’s Hawk field season is different. This year the nesting season lasted a month longer than 2023. Fledglings were either more wary of traps or were too well fed to be bothered to hunt for themselves, resulting in a downturn in the number banded, despite diligent efforts.
Two youngsters near the Pattihood nest (John Gossman)
Old Blue
Male Coop blue right E-V (“Old Blue”) successfully nested in Seattle’s Northacres Park for 13 consecutive years, fledging 49 offspring. He was not found in the park this year. Searches by Don McCall, Steve Garmanian, Jeff Graham, Martin Muller and Ed Deal combined for 27 site visits from March to July without success. Although he probably died, we prefer to think he moved a few blocks away and nested in a hidden location.
Larry Gilpin’s timely photo of Old Blue graces the back cover of the 2024 issue of British Columbia Birds. Congratulations, Larry.
Systematics
Genetic researchers recently “moved” the Cooper’s hawk and several other Accipiters to a different genus. The Cooper’s Hawk, formerly Accipter cooperii, is now named Astur cooperii. Other species moved to the genus Astur include the American Goshawk (A. atricapillus) and Eurasian Goshawk (A. gentilis). The sharp-shinned hawk remains in the genus Accipiter (Accipiter striatus).
Jack Bettesworth (Elaine Chuang)
Volunteer Profile
Veteran birders and new Coop volunteers Darwin Nordin and Rebecca Watson scoured the dozen West Seattle Coop territories this season, providing hard-won and critical information. Besides their extensive reporting on known nesting pairs, they found their first new Coop nest: a second pair in Fauntleroy Park. They have certainly earned the title of Rookies of the Year.
The Coop Season by the Numbers
Over 2,000 site visit reports were compiled from 25 core volunteers.
- 65 nest-building pairs (66 in 2023)
- 9 nest-building pairs failed to lay
- 3 nests failed during incubation
- 2 nests failed after hatching
- 51 nests fledged young (55 in 2023)
- 183 fledglings (200 in 2023)
- 34 fledglings color-banded
(43 in 2023)
Number Crunching I:
Juvenile Female Age at First Nesting
Population studies are essential to monitor the health of a raptor population, but they are difficult to conduct. One controversy resolved in the last few years is the age of a Cooper’s hawk at first nesting. It was long thought that most one-year-old birds were “floaters”, biding their time to nest until they were two years old. Research by Brian Millsap and colleagues in Albuquerque documented that all females in their study that lived to one year old nested while still in juvenile plumage.
In Seattle, for the period 2013-2024, we documented 122 nest-building pairs comprising a one-year-old (juvenile plumage) female and an adult male. Of these 122 juvenile female/adult male nest-building pairs, 91 (75%) succeeded in fledging a total of 313 youngsters, or 3.4 fledglings per successful pair. For the same period, we found 414 adult/adult nest-building pairs, of which 347 (84%) succeeded, cumulatively fledging 1292 young (3.7 per successful pair). These productivity numbers are consistent with those reported by the Millsap group: nesting juvenile females have slightly smaller fledgling counts and a slightly higher failure rate compared to adult/adult pairs.
Number Crunching II:
Juvenile Male Nesting
Although all one-year-old females attempt to nest, one-year old males almost never do. In a data set of 728 nesting pairs of known plumage published by Wisconsin Cooper’s hawk guru Bob Rosenfield, only 13 (1.4%) of the males were in juvenile plumage. We have found a similar pattern. Out of 563 nest-building pairs in 2013-2024, we identified only 27 (4.8%) juvenile males. Eighteen (67%) of these pairs fledged young, compared to an 84% success rate for adult pairs. Juvenile males also showed lower fledgling numbers (2.6 per successful nest compared to 3.7 in adult pairs). One conclusion is that males take longer to acquire and hold a territory and to effectively hunt to feed a family. The few one-year-old males that do nest successfully, such as Old Blue, certainly have “the right stuff.”
Below, adult female P-4 enforcing an orderly feeding of the fledglings, no easy task (John Gossman)
Selected Band Reports
Popular Female
In 2023, adult female orange right 9-C nested in Fauntleroy Park, West Seattle. Her nest failed early in incubation. Shortly afterward she was seen courting and nest-building 2 km away on Orchard St. She successfully nested there with a second-year male, fledging three. In 2024 she courted an adult male on Orchard St. while also courting an adult male in Fauntleroy Park, both unbanded. This year she decided that Fauntleroy was the better choice. She fledged three there. The Orchard St. male failed to recruit a replacement female. This is the third documented instance of a banded female courting two males in neighboring territories. We published the first two records for this species in the Journal of Raptor Research in 2017. Thanks to the West Seattle “Coopnoscenti” for tracking orange 9-C at both locations.
Good Parents
Four-year-old male purple left S-5 nested for the 3rd year with female orange right P-4 (at least 4 years old) in the Pattihood territory in Fremont, this year fledging five. They wisely nested outside the window of our volunteer John Gossman, who subsequently compiled an impressive photographic chronicle of this Coop family.
Traveling Male
Four-year-old male purple left 8-6, banded 31 July 2020 as a fledgling in Kubota Garden, was photographed 2 May 2024 in a yard in the town of Snoqualmie Ridge. This is 18 miles from his natal nest, an unusually distant dispersal for a Coop male. He was previously photographed in the same neighborhood in February 2022. Typically, male Coops first nest when they are two years old, so he likely has nested in the area for three years (2022-2024). Although about 30 of our banded fledglings have later been found nesting in Seattle, no Coop has been found nesting outside the city. A search party is planned for mid-March 2025.
Adult male 8-6 (Gary Anderson)
Close-up of band orange 9-C (Jeremiah Holt)
A Formidable Predator
On Halloween, Gary Maxwell received quite a treat. He witnessed and photographed an adult female Coop take a drake Northern shoveler at Yesler Swamp, Union Bay Natural Area.
Two Humility Lessons
After 13 years of searching for Cooper’s hawk nests we occasionally delude ourselves that we have located all the nests in the city. This year two banded adults reminded us that despite all our efforts we are missing nests. These humility lessons teach us that our data represents the minimum number of Coop nests in Seattle.
1
3 July 2024 – Three-year-old male purple left R- 6, banded 10 July 2021 as a recent fledgling at Miller Park on Capitol Hill, was photographed in a yard in the Madison Valley (near Martin Luther King Jr Way & John St.). Given his known age, he must have nested somewhere in the area in 2023 and 2024.
2
23 August 2024 – Adult female orange right E-M, was banded as an adult in Magnuson Park on 11 March 2021. She nested there in 2021 and 2022. She was last seen 22 March 2023 in Magnuson Park. She was recently photographed twice at the Union Bay Natural Area. It is unknown where she spent the 2023 and 2024 nesting seasons, but likely somewhere between Magnuson Park and the Union Bay Natural Area.