RED-SHOULDERED HAWK in Idaho
by Harry Krueger
(Adapted from message to IBLE, 28 December 2004)
Last Wednesday (23 December, 2004) Cliff and Lisa Weisse discovered a Red-shouldered Hawk approximately 3.1 miles east on ID 78 from its intersection with ID 45, alongside the Snake River in riparian habitat with some mature Cottonwoods on both sides of the river. Despite searching by Stacy Peterson and myself that evening before sundown, the bird could not be relocated. On the proceeding day (24 December, 2004), I was able to refind an adult Red-shouldered Hawk (presumably the initial bird observed by the Weisse's) after quite some time (one hour) searching, this time approximately 1/4 miles downstream in Cottonwood trees. All obvious indications point to this being of the "California" subspecies, Buteo lineatus elegans (which also resides in southern Oregon, western Nevada, western Arizona, and Baja California).
There are four (and according to some authorities, five) subspecies of Red-shouldered Hawk. Only one is "western," while the nominate race, B. l. lineatus, breeds in the Northeast and is migratory to as far south as Florida and central Mexico. There are two (or three) other races in the Southeast, alleni and extrimus (and possible texanus, which B.K. Wheeler considers part of alleni in his Raptors of Eastern North America).
Red-shouldered Hawk has become a "regular" vagrant to Idaho, recently with three reported last Fall and one this Fall (three birds at Lucky Peak and one at American Falls), but, to my knowledge, in no case has there been a notation or documentation as to subspecies . It has been most likely been assumed, by those aware of the differentiation, that these birds were probably elegans. But there is now new reason to look carefully at any Red-shouldered Hawk seen in the West.
On 26 September, 1996, a dead Red-shouldered Hawk was found in Sacramento, CA and in August, 2001 the identification of this bird was confirmed as of the "eastern" race, lineatus, at the National Museum of Natural History, Washington, D.C. Until this point, the only verified record of lineatus was from Colorado, as well as ten migration season records from the eastern portion of that state, which were probably lineatus.
The significance for Idaho of this record is that now more than ever, every Red-shouldered Hawk encountered in this state should be carefully studied to try to confirm subspecies, and therefore in so doing, geographic origin. As confirmed observations of Red-shouldered Hawk in the Northwest and Great Basin increase, the possibility of B. l. lineatus becomes a viable possibility.
How does one differentiate between the two subspecies, elegans and lineatus? First, although B. l. elegans is larger than the "Eastern" races of this buteo, that is a characteristic difficult to judge in the field. The most obvious characteristic in adult birds is an unstreaked, brighter rufous-orange wash to the breast. Also, the crown is paler (lineatus is dark centered), and upperpart feathers have broad rufous edging, giving a brighter "orange-shoulder" effect, whereas lineatus has thin edging. Elegans has blacker greater coverts and secondaries with distinct white bars, whereas those in lineatus are dusky with indistinct pale bars. The tail on elegans shows very bold (3-5) bars, whereas its eastern counterpart has seven indistinct, pale bars. Lineatus has a dark throat, while on elegans it is quite pale.
In sub-definitive plumage or immature plumage elegans is more similar to the adult birds of its race, with their underparts more barred than streaked, the crescent shape of underwing paler rufous, and the tail a darker brown, with whitish pale bands.
Through careful observation a renewed consideration should be given to the subspecific status of any Red-shouldered Hawk seen in Idaho, especially in consideration of the recent California record of B. l. lineatus, or the nominate eastern race.