Cooper's & Sharp-shinned Hawk: Study skins + ID Notes

Transcription

1 Cooper's & Sharp-shinned Hawk: Study skins + ID Notes On 23 January 2014 I spent a few hours at the Canadian Museum of Nature Collections Facility in Gatineau, QC. The focus of the visit was Accipter ID; specifically, Sharp-shinned (SSHA) and Cooper's Hawk (COHA) identification. I also spent some time with the Northern Goshawk (NOGO) skins and have included some notes/photos on that species, as well. Accipiter ID is real challenging - most especially differentiating between A) Sharp-shinned vs. Cooper's Hawk and B) Juvenile Accipiters. My hope is that the collection of photos below serve as an identification and learning resource. Note: the idea for these photos/captions stems from a browse of this webpage: A quick note on size: I use terms like "small", "typical", and "large." These terms coincide with the averages presented on BNA & Cornell. At the CMN, each study skin is tagged and details like length and weight are visible on each respective tag. I used what I knew of each species' size range (below) to form size judgments in relation to averages. Sharp-shinned Hawk: Both Sexes: Length: in. Weight: g Cooper's Hawk: Male Length: in. Weight: g. Female Length: in. Weight: g Northern Goshawk: Both Sexes: Length: in. Weight: g Figure 1: (L to R): Large adult female Sharp-shinned Hawks and small adult male Cooper's Hawk. Large female Sharp-shinneds are quite close in size to small male Cooper's. In the field, this particular Cooper's thin tubular body, relatively long wings with a straight leading edge, relatively long tail, slate blue back, pale nape, and dark cap would help to differentiate it from the Sharpie camp.

2 Figure 2: (L to R): Adult female Sharp-shinned Hawks and adult male Cooper's Hawk. Figure 3: Close-up of Sharp-shinned Hawk (left) and Cooper's Hawk (right) tails. Note how the square (SSHA) vs round (COHA) tail tip ID point doesn't apply all too well in this case. Imagine the difficulty noticing the subtle rounded edges of this particular Cooper's Hawk's tail in the field?

3 Figure 4: Sharp-shinned Hawk (left) and Cooper's Hawk ventral view of tail. Note in the Cooper's (right), the outermost tail feathers are shorter than the rest; this feature is the primary producer of the round tail tip appearance, but the tail feathers must be held at a certain orientation for this effect to be clearly observed in the field. So far, in my VERY short experience in the field (3 years) I haven't been able to place much trust in this commonly used ID feature (tail tip shape). Many Sharp-shinned have appeared round tail-tipped and many Cooper's have appeared square tail-tipped. Figure 5: (L to R): Ventral view: Sharp-shinned Hawk (small adult male), Sharp-shinned Hawk (typical adult male), Sharp-shinned Hawk (large adult female), Sharp-shinned Hawk (large adult female), Cooper's Hawk (small adult male).

4 Figure 6: (L to R): Dorsal view: Sharp-shinned Hawk (small adult male), Sharp-shinned Hawk (typical adult male), Sharp-shinned Hawk (large adult female), Sharp-shinned Hawk (large adult female), Cooper's Hawk (small adult male). Figure 7: The only in-the-field constant: Variation! (L to R) - Sharp-shinned Hawk (typical adult male), Sharp-shinned Hawk (small adult female), Sharp-shinned Hawk (typical adult female). I wonder how many Sharp-shinneds I've passed off as males due to miniscule size? The reality is probably too terrifying to digest in one thought alone..

5 Figure 8: (L to R) - Ventral view: Cooper's Hawk (typical adult female) Cooper's Hawk (typical adult male), Cooper's Hawk (small adult male), Sharp-shinned Hawk (large adult female). The rightmost pairing offers an example of how close in size large Sharpies are to small male Cooper's Hawks. Figure 9: (L to R) - Dorsal view: Cooper's Hawk (typical adult female) Cooper's Hawk (typical adult male), Cooper's Hawk (small adult male), Sharp-shinned Hawk (large adult female). Note the distinct capped appearance of the male Cooper's Hawks. Both male and female Cooper's show a cap - males show a greater contrast (light slate lower nape and dark gray cap).

6 Figure 10: (L to R) - Ventral view: Northern Goshawk (large adult female), Cooper's Hawk (typical adult female), Cooper's Hawk (typical adult male), Sharp-shinned Hawk (large adult female). This female goshawk must've been a real terror throughout its territory. Study skins are inconsistent in terms of authentic length, girth, overall size of each of the respective birds, however, this Northern Goshawk specimen certainly highlights what can be seen in the wild with a live specimen: immensely broad, tubular, and powerfully built body. One of the best gos' pics, IMHO, is the first gos' pic (adult male) in Wheeler's photographic guide to NA raptors. The characteristic broad chest is captured perfectly in that photo! Figure 11: (L to R) - Dorsal view: Northern Goshawk (large adult female), Cooper's Hawk (typical adult female), Cooper's Hawk (typical adult male), Sharp-shinned Hawk (large adult female).

7 Figure 12: (L to R) - Ventral view: Juvenile male and female Sharp-shinned Hawks (L) male and female Cooper's Hawk (right). Accipiter sexual dimorphism (male/female size difference) is legendary. Note the M/F size difference between these typically-sized specimens. Figure 13: (L to R) - Dorsal view: Juvenile male and female Sharp-shinned Hawks (L) male and female Cooper's Hawk (right). Note the tawny napes of the Cooper's Hawks. Sharp-shinned Hawks can show tawny napes but this is less frequently observed (Liguori, 2011). Note how the tail of the female Sharp-shinned Hawk appears quite rounded, and the male Cooper's Hawk to its right shows a squarish tail. These study skins are effective because they reveal real life ID pitfalls quite well!

8 Figure 14: Dorsal view of juvenile Cooper's Hawks (4 males, 1 female). A 5-bird-sample size to showcase a consistent feature as described by Liguori, Sullivan, Wheeler, Clark, etc: tawny head and nape contrasting with a brownish back. Juvenile Cooper's Hawks show a tawny wash to the head, and, while juvenile Northern Goshawks may show this trait, most Sharp-shinned Hawks do not (Liguori, 2011). Note how the round tail tip appearance is apparent when the tail feathers are held at a specific orientation, otherwise, (like bird 1 and 3), the tail tip appears quite square-ended. Figure 15: Ventral view of Cooper's Hawk (juveniles: 4 males, 1 female). Note relatively fine streaks, heaviest along the lower chest and belly, lightening towards the vent and undertail.

9 Figure 16: Dorsal view of Sharp-shinned Hawk (juveniles: 5 males, 1 female). Figure 17: Ventral view of Sharp-shinned Hawk (juveniles: 5 males, 1 female). Note globular, thick streaks extending from the upper chest down the belly and towards the vent. With Cooper's juveniles (in most cases) streaking really thins out toward the lower belly, unlike most Sharp-shinned Hawk juveniles.

10 Figure 18: (L to R) - Dorsal view: Cooper's Hawk (large, heavily-marked juvenile female), and Northern Goshawk (typical juvenile male). A juvenile Northern Goshawk is a tawny bird and the tawny is a consistent wash throughout its entire plumage. Note the lovely wave-like tail bands in comparison to the Cooper's Hawk. Note also that the wavy bands are rimmed with paleness. Figure 19: (L to R) -Ventral view: Cooper's Hawk (large, heavily-marked juvenile female), and Northern Goshawk (typical juvenile male). Juvenile Northern Goshawks have heavy, globular coalescing streaks that extend, in equal frequency, from the upper chest down throughout the belly and towards the vent. The undertail coverts of a juvenile Northern Goshawk are consistently streaked/spotted. Some Cooper's Hawks show streaked/spotted undertails, but much less consistently so.

11 Figure 20: (L to R) - Dorsal view: Juvenile Cooper's Hawk and Northern Goshawk tails. The undeniably unique tail pattern of a juvenile Northern Goshawk! Compare & Contrast Figure 1: Cooper's Hawk (left) and Sharp-Shinned Hawk (right) juveniles - ventral view. I adjusted the size of the hawks in the photo so the size discrepancy between Cooper's and Sharp-shinned isn't distracting from focusing on plumage details. Figure 2: Cooper's Hawk (left) and Sharp-Shinned Hawk (right) juveniles - dorsal view. I adjusted the size of the hawks in the photo so the size discrepancy between Cooper's and Sharp-shinned isn't distracting from focusing on plumage details. References Liguori, J Hawks from Every Angle. Princeton University Press (Princeton, N.J.). Liguori, J Hawks at a Distance. Princeton University Press (Princeton, N.J.) Jon Ruddy, Ottawa, Ontario