Birding Magazine

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WebExtra Feature—supporting material for "A Study of Krider's Red-tailed Hawk" Birding Volume: 42 Number: 2 Pages: 38-45.
 

Krider's Hawk Photo Captions

Fig. 1 – Breeding adult male Krider's. This bird has a white tail with well-defined, thin subterminal, but has markings on the underparts that are more Eastern-like. Many female Krider's nesting in the Dakotas were more heavily marked than males, and difficult to distinguish from pale Easterns. North Dakota, July, photograph by Brian Sullivan.

Fig. 2 – A typical Krider's. Birds this pale were often males of breeding pairs in the Dakotas. Note white-based tail with narrow subterminal, white head with darker malar, relatively unmarked buffy underparts, rufous-toned carpals, and faintly banded remiges. Mississippi, December, photograph by Brian Sullivan.

Fig. 3 – A very pale adult Krider's showing all white head, frosty white upperparts and minimal body markings below. Note pinkish tail with narrow subterminal band. Oklahoma, January, photograph by Larry Hancock.

Fig. 4 – Typical adult Krider's. The bird at left is a breeding male from North Dakota. Note white head with dark malar, white mottling on upperwings, and white tail with distinct narrow subterminal. The bird at right is a wintering female type, with darker head, distinct malar, and extensive white and rufous mottling above. Note pale red tail shown by some Krider's. Left, July, photograph by Brian Sullivan. Right, Texas, December, photograph by Brian Tang.

Fig. 5 – Breeding adult Krider's. Many have white restricted to the tail base, but note white head with distinct dark malar, and relatively unmarked underparts. North Dakota, July, photograph by Jerry Liguori.

Fig. 6 – A similar bird to that in Fig. 1. This bird has a typical Krider's tail (note well-defined, thin subterminal), and white crown, but has a more distinct bellyband and patagial bars than most. Many of the breeding females in the Dakotas approximate this plumage type. Mississippi, December, photograph by Brian Sullivan.

Fig. 7 – Adult Krider's or possible Krider's x Eastern intergrade. Female types can be difficult to categorize to race specifically as they are generally more heavily marked. Note pale crown, mostly unmarked buffy underparts with darker carpals, and a white-based tail with narrow subterminal. This bird is likely a female Krider's, but caution is warranted when identifying birds like this away from known breeding areas. Mississippi, December, photograph by Brian Sullivan.

Fig. 8 – Adult Krider's or Krider's x Eastern intergrade. A similar bird to Fig. 7. Note unmarked buffy underparts, pale crown and face, pale reddish tail, and unmarked remiges shown rarely by some Krider's and often by adult light-morph Harlan's. Mississippi, December, photograph by Brian Sullivan.

Fig. 9 – Adult Krider's or Krider's x Eastern intergrade. Note pale crown, extensive white mottling above, with rufous tones on the upperwing coverts and near the tips of the inner primaries. The all red tail is atypical for Krider's, but can be shown by some adults. Oklahoma, January, photograph by Larry Hancock.

Fig. 10 – Typical adult Krider's. Note whitish head with dark malar, unmarked buffy underparts, and white-based tail with distinct narrow subterminal. Oklahoma, January, photograph by Larry Hancock.

Fig. 11 – Adult Krider's with moderately marked underparts. When seen from below these can be difficult to distinguish from Easterns, but note pale crown. The bird at left is a North Dakota breeder with an all white tail above with narrow dark subterminal (Fig. 3b in Birding), the bird at right a wintering individual. Left, July, photograph by Brian Sullivan. Right, Oklahoma, November, photograph by Larry Hancock.

Fig. 12 – Juvenile Krider's or Krider's x Eastern intergrade. More needs to be learned about plumage variation in juvenile Krider's. Some birds such as this show a mix of characters between Krider's and Eastern. This bird shows many Krider's traits, such as a whitish head and face, pale brown tail with narrow dark bands, and lightly banded flight feathers. Mississippi, December, photograph by Brian Sullivan.

Fig. 13 – A more typical juvenile Krider's. Note white head with dark malar and eye-line, bold white primaries, white-based tail with narrow dark bands, and lightly marked underparts. Juveniles with completely white underparts are uncommon; most have indistinct patagials and bellybands. Oklahoma, January, photograph by Jim Lish.

Fig. 14 – Molting juvenile Krider's. The bird at left has replaced several tail feathers (odd for December), but shows the change over from whitish-brown juvenile to red with pale base of adult. The probable male at right was photographed in July and is molting from juvenile into adult plumage. Again, note the whitish juvenile tail feathers and 'pinkish' adult central tail feathers with narrow dark subterminal. Oklahoma December, photograph by Jim Lish. Right, North Dakota, photograph by Jerry Liguori.

Fig. 15 – Three Krider's type juveniles. The bird on the left fledged from the same nest as the white-headed fledgling shown in Fig. 1d of Birding, albeit several years later. Note the creamy head with dark malar, and extensive white mottling above. The middle bird is a white extreme juvenile taken during winter. Note the unmarked white head, white tail with narrow blackish bands, and extensive mottling above. The bird at right is from July in North Dakota. Note the pale head and face, and pale tail with new red adult central tail feather. This bird could be a Krider's x Eastern intergrade. Left, South Dakota, July, photograph by Brian Sullivan. Middle, Oklahoma, February, photograph by Mark Dreiling – Dan O'Donnell. Right, photograph by Jerry Liguori.

Fig. 16 – Juvenile Red-tailed Hawk, presumably a Krider's x Eastern intergrade. Note pale crown, barred outer primaries shown by some Krider's and Easterns, rufous highlights on inner primaries and primary coverts, and reddish tail with narrow dark bands. Montana, September, photograph by Stephen Wilson.

Fig. 17 – Juvenile Red-tailed hawk, presumably a Krider's x Eastern intergrade. Similar to Fig. 16. Note Eastern-like bellyband, underwing markings, and head but Krider's-like whitish upperwing mottling and primaries, and pale brownish tail. Minnesota, November, photograph by Stephen Wilson.