WatchList Species Account for Allen’s Hummingbird (Selasphorus sasin)

Qualifies for the list as a Declining Yellow List Species

 

Allen's Hummingbird

Photo: Glen Tepke

The Allen’s Hummingbird has one of the most restricted breeding and wintering ranges of any U.S.-breeding hummingbird, or for that matter, any bird. Found in a narrow band along the Pacific Coast from southwestern Oregon to southern California, including several of the Channel Islands (where it is resident), the migratory population winters in a small area of central Mexico, though the nonbreeding range is not well known. It is very similar to the closely-related Rufous Hummingbird, and the two species apparently hybridize. Female and juvenile Allen’s and Rufous Hummingbirds cannot be safely distinguished from one another in the field.

 

The Allen’s migratory pattern is unusual; it arrives on the breeding grounds in the middle of winter, having departed Mexico as early as late fall, and males depart the breeding grounds as early as late spring. Breeding habitat is the moist coastal belt affected by summer fogs; in nonbreeding its habitat includes forest edge and scrub clearings with flowers.

 

The Channel Islands contain a number of hummingbird-pollinated plants, including endemic species, that rely on the Allen’s for pollination, as other hummingbirds are uncommon there. Males on territory have a complex and spectacular dive display, including swinging back and forth in a symmetrical, penduous arc, complete with pauses, shaking of the body, and emitting a loud buzz and a metalic shriek.

 

As for population trends, Breeding Bird Surveys are not well suited to detecting changes in this species, due to the fact that the surveys are generally run after the male birds have begun to depart, and at any rate, detected males do not represent nesting pairs.

 

Human activity has a great effect on this species, particularly through planting of eucalpytus groves and other exotic trees which serve as ample nectar supplies, particularly benefiting the nonmigratory Channel Islands birds. Plantings on the mainland have favored the Anna’s Hummingbird, which has a competetive advantage over the Allen’s, and may have depressed its numbers. Further work on the biology of the Allen’s is needed, this work is made harder by the fact that it is nearly impossible to separate the females and juveniles of the species from the Rufous in the field.