Featured Photo

Now that the American Ornithologists Union (A.O.U.) has split the Canada Goose (Branta canadensis) into two species (Banks et al. 2004) field birders are faced with the not inconsiderable problem of telling the two apart.This identification issue is especially challenging for birders in the West, where a number of races of both species occur.Of the four subspecies that now constitute the Cackling Goose (Branta hutchinsii), the nominate Richardson's Cackling Goose (B.h.hutchinsii) is almost unknown west of the Rocky Mountains (A.O.U 1957), while the diminutive and very dark Cackling Goose proper (B.h.minima) is unlikely to be mistaken for any form of the Canada Goose.The Aleutian Cackling Goose (B.h.leucopareia) has features, such as a complete white ring at the base of the black neck, that make identification of most individuals straightforward.Conversely, most individuals of three of the four western subspecies of the Canada Goose are either too large and pale (Great Basin Canada Goose, B.c. moffitti), or too large and dark (Vancouver Canada Goose, B.c. fulva, and Dusky Canada Goose, B. c. occidentalis) to be confused with Cackling Geese.Please note that I said "most."The subject of this issue's Featured Photo is the identification of the two subspecies of these now full species that resemble each other most closely.Taverner's Cackling Goose (B.h.taverneri) has been recognized as a subspecies distinct from the Lesser Canada Goose (B.c.parvipes) only since the 1950s (Delacour 1951).Indeed, the A.O.U.(1957) did not include taverneri in the 5 th edition of its checklist, and Palmer (1976) believed Taverner's to be only the darker individuals of a clinal population of parvipes.However, genetic work has shown that breeding populations of taverneri fit neatly with other Cackling Geese, and those of parvipes belong to the Canada Goose complex (see the citations in Banks et al. 2004).The upper photo shows an individual believed to be B.c. parvipes, the middle photo depicts an apparent B. h.taverneri, and the bottom photo compares the same two individuals resting side by side, with the parvipes on the left.I believe both these individuals are adults, on the basis of the broadness of the body feathers and the nice, neat rows of pale edging on the back and wing coverts.These photos were taken in Arrowhead Marsh, Alameda County, California, in January 2004.Compare them with photos of a juvenile apparent taverneri on the World Wide Web at www. badboybirding.com/CAGO_l 1262003.htm.Delacour (1954) described these two forms as follows: parvipes "similar to moffitti in shape and proportions, particularly the long bill and neck, and also generally in color, although varying a little more in tone, but much smaller"; taverneri "resembles B.c. parvipes but smaller with shorter bill and neck, and generally darker, although very variable in color, some specimens being as pale as parvipes, others as dark as leucopareia."More recent treatments of Canada Goose identification haven't added much, but Johnson et al. (1979) found that the breast of taverneri is typically grayish, but quite variable, and frequently lighter in young birds, whereas parvipes has a pale breast, "sandy" colored rather than the brownish of leucopareia or the darker grayish of taverneri.These authors discussed white neck rings, noting that 40% of adults and 10% of immatures of taverneri have complete neck rings averaging 3-5 mm wide, with an additional 20-30% showing incomplete or trace neck rings.In their much

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.