Bird of the Week: Semidi Islands Cackling Goose

This neck-collared Semidi Island Aleutian Cackling Goose was photographed at the Martella Dairy Farm at Woods, Tillamook County, Oregon on 10 April 2011 . Note the lack of a conspicuous white ring at the base of the black "neck sock." (Photo by Dave Irons)

The Semidi Islands population of Cackling Goose ranks among the rarest of all North America birds, but is virtually unknown to most birders. Unless you visit Woods/Pacific City, Tillamook County, Oregon between October and April or somehow make your way to the Semidi Islands off southwestern Alaska during the nesting season, your chances of seeing one are nil. 

The species split of "white-cheeked" geese in 2004 separated the smaller more northerly breeding taxa to a new species -- Cackling Goose (Branta hutchinsii). Though some sources had already treated this wide-ranging group of "small race" Canada Geese as a de facto species, the American Ornithological Union (AOU) continued to ascribe all white-cheeked geese to Canada Goose (Branta canadensis), with a varying number of  subspecies.

Currently, there are four recognized subspecies of Cackling Goose: Ridgway's (B. h. minima), Taverner's (B. h. taverneri), Aleutian (B. h. leucopareia) and Richardson's (B. h. hutchinsii). Ridgway's, Taverner's and Aleutian all breed in Alaska and for the most part their winter ranges are restricted to the Pacific Flyway, while the nominate Richardson's nest farther to the east and winter primarily east of the Rocky Mountains. (Mlodinow et. al 2006).

The Semidi Island birds are considered a sub-population of the now recovering, but once critically endangered, Aleutian Cackling Goose. In terms of appearance, the Semidi birds are, perhaps, more variable than other sub-populations of Aleutians. Based on personal observations, they seemed to consistently show more rounded heads and a flatter forehead profile, though posture and viewing angle can affect these aspects of an individual bird's structural appearance. Seemingly all of  of the banded Semidi Island birds we saw either lacked the conspicuous broad white ring or partial ring at the base of the foreneck (shown by most Aleutians) or the white was very restricted. However, according to U.S.F.W.S. Roy Lowe (pers. comm.), Semidis can show broad white neck rings. Finally, in side-by-side comparisons Semidis often seemed to be shorter-legged than presumed non-Semidi Aleutians.

The bird with the green neck collar is a known Semidi Island Aleutian Cackling Goose (banded on the nesting grounds). Although the other birds differ in head shape and overall pattern (particularly the darker right hand bird), they may also be Semidis according to U.S.F.W.S. biologist Roy Lowe. (Photo by Dave Irons)

Collectively, the Semidi Islands provide slightly less than 12 square miles of land mass and the geese are only nesting on two islands in the cluster. The entire population of Semidi Islands Cackling Goose numbers between 120 and 140 birds (Jarvis 2003, Lowe pers. comm). In the wake of massive recovery effort (mainly involving the eradication of introduced Arctic Foxes on the breeding grounds) Aleutian Cacklers, once feared at the brink of extinction, have seen dramatic population increases. However, the Semidi Islands population, which at the start of recovery efforts numbered about 70 birds,  quickly hit the current plateau (about 120 birds). Some have suggested that inbreeding may be a limiting factor when it comes to growing the population (U.S.F.W.S 2001). There is no recent evidence of interbreeding between Semidis and more widespread Aleutian populations. 

The Semidi Islands, located in the bottom left corner of the map, are off the southwest corner of Alaska just east of the Aleutian Island chain. (Map image sourced online at: http://en.wikipedia.org/wiki/File:Kodiakislandmap.png)

Each Fall, traveling en masse, this modest flock of Cackling Geese makes the 1400-mile journey south from the Semidi Islands to a single dairy pasture along Oregon's northern coast. Once there, they will spend the next seven months grazing an area that is no more than one mile in diameter. Each evening the flock makes a short flight (perhaps two miles) to roost on the ocean or on Haystack Rock, which lies a few hundred yards off of Cape Kiwanda at the north end of Pacific City (Jarvis 2003). In 1979, when the Semidi Island breeding population was discovered (Mlodinow et al. 2006), virtually no white-cheeked goose could be found wintering along the Oregon Coast. However, with the establishment of the nearby Nestucca Bay National Wildlife Refuge in 1991 and the rebounding populations of several white-cheeked goose taxa, many hundreds and perhaps thousands of Canada and Cackling Geese now winter in the Nestucca River pasturelands. About 10% of the known population of Dusky Canada Goose (B. c. occidentalis), which numbers fewer than 10,000 birds, can be found in this area October-April (U.S.F.W.S/Nestucca Bay profile). 

I've known about the Semidi Island Cackling Geese for about 6 or 7 years after seeing a feature produced by Oregon Public Broadcasting, but only recently got to see this flock for the first time. Living in western Oregon, I see Cackling Goose flocks on a daily basis from late October through April. It is not unusual to see a field with several thousand birds feeding shoulder to shoulder and at certain locales daily counts can number into five digits. In this context, it's hard to fathom that a nesting population of fewer than 150 birds can persist at such a fragile level with no apparent recruitment from other populations. A single environmental disaster or an exceptional storm during their migratory flight or on the wintering grounds could conceivably decimate the entire flock in a single event. As I watched and photographed and pondered such possibilities, I could only marvel at the resiliency of  these birds.

Sources cited: 

Jarvis, Robert L. Canada Goose. Pp. 82-86 in Birds of Oregon: A General Reference. D.B. Marshall, M.G. Hunter, and A.L. Contreras Eds. 2003. Oregon State University Press, Corvallis, OR.

Mlodinow, S.G., P.F. Springer, B. Deuel, L.S. Semo, T. Leukering, T. Doug Schonewald, W. Tweit, and J.H. Barry. 2008. Distribution and identification of Cackling Goose (Branta hutchinsii) subspecies. North Amer. Birds 62: 344–360.

Editor's Note: We are introducing a new feature to the BirdFellow online journal. Each week we will do a short feature on a species or subspecies of interest. We will endeavor to share stories about unique populations, subspecies, or an interesting behavior that one might see in a common bird. If you have a story you want to tell, this venue is not limited to a select few. We want our online journal to be a place where community members can publish as well. We will be happy to work with you to find and edit photos and edit your writing if needed.