The Migrations of Allen's and Other Hummingbirds

Abstract

tually migrates southward in numbers in late spring; further, its route soon veers away, geographically and ecologically, from the northward return route used chiefly in winter. Allen's Hummingbird (Selasphorus sasin) is remarkable in that it breeds only in California, barely overlapping that State's borders, and normally (at least until recent years) only in a narrow coastal strip. Of the few endemic California species, it is the only wholly migratory one! This distinction belongs to the northern, nominate race. The southern S. s. sedentarius Grinnell has the opposite distinction of being the only virtually sedentary hummingbird or nectar-feeder of any kind in the continental United States (see below). These amazing, somewhat elliptical migrations at the wrong seasons remain unappreciated because of: (1) the few records, mostly unpublished, between early September and mid-February; (2) reluctance to admit migrations in Californian endemics or ignorance in official check-lists (cf. for example, Swarth 1914:38, 90, on both Allen's and Anna's Hummingbirds, Calypte anna, in Arizona); (3) their seasonal displacement; and (4) failure to distinguish age/sex classes, or even the species (vs. the extremely similar Rufous Hummingbird, Selasphorus rufus), whose migrations are asynchronous. Authorities disagree widely on migrations and winter ranges (see A.O.U. 1931, 1957, Berlioz 1932, Friedmann et al. 1950). Loye H. Miller first pointed out (in Willett 1933:97) that even adult males of Allen's Hummingbird are not always safely distinguishable in color. This important fact is still generally overlooked; Peterson and Chalif (1973), Robbins et al. (1966), and Stiles (1972:31) all described the back of adult male S. rufus as rufous, or sometimes with scattered green feathers, thus not contrasting to the rufous tail and coverts as in S. sasin. But