It's All in the i-Details - What's an Accipiter?
Updated: Dec 29, 2021
I have to admit, I’ve been avoiding the tricky topic of accipiters on this blog. What’s an accipiter you ask? In Latin, it just means “bird of prey”, but it’s also the genus or first part of the scientific name for Sharp-shinned Hawk, Cooper’s Hawk and Northern Goshawk. Since the first two species are frequent fliers in London, I’ll just focus on distinguishing between them.
Many people agree that “bird hawks” are near the top of their list for universally challenging identifications, beaten out perhaps by gulls and fall warblers. Hawks make me ID-hesitant, to the point of intimidation, so I present this summary under no pretense of being an expert. My confidence picked up on Christmas Day, however, when I saw a shape fly up to a tree next to the house. Noting a few field marks, backed up with a few camera shots for study, I quickly determined that the bird looking down was a Sharp-shinned Hawk. Its presence also explained why all the feeder birds had disappeared in the past hour!
There are so many things to consider when looking at a puzzling neighbourhood hawk. Deciding which of three main hawk groups it’s in needs a lesson unto itself― buteo, falcon or accipiter? Entire books have been devoted to hawk ID, so this blog will just be the Cliff notes of the Cliff notes on one of those groups, accompanied by a few photos for guidance. In a quick summary, buteos can be represented by the commonly seen Red-tailed Hawk, that roadside sentinel perched on poles or tree tops in open areas. Buteo wings are broader, bodies more robust and tails wider than accipiters and they can be seen soaring in circles scanning for their main food - rodents. Unfortunately, for identification this isn’t a hard and fast rule, since I have seen them bursting through the forest on a foray in squirrel-rich woodlots. They show some streaking down the front but usually it’s restricted to a “belly band”. Oops, another caveat... accipiters can also be seen aloft, soaring in circles. Sigh, you see how perplexing identification can be.
Falcons are raptors with narrow pointed wings in flight silhouette and like accipiters, pursue their bird prey in surprise attacks on the wing. Sometimes, the heavily streaked Merlin (a local falcon) is mistaken for one of the accipiters. It’s darker, a wee bit smaller than a Sharp-shinned Hawk and has a hint of facial sideburn reminiscent of a Peregrine Falcon.
Performing sleek aerial manoeuvers is a successful chasing strategy for accipiters, so, many times the only view you get is brief and obscured by branches as the hunter weaves through the trees... departing with only a tail-end glance. Not too helpful for an already difficult ID of Sharp-shinned vs Cooper’s Hawk.
To tackle an identification, the viewer first needs to decide whether the bird is adult or immature. The ages can look quite different. Adults show dense rusty-toned horizontal barring down the front of the breast. Juveniles and immature birds have thinner, brown, vertical teardrop streaks, distinct against a white feather background. Same goes for eye colour; adult eyes are reddish, youngsters have pale yellow and sub-adult eyes blaze an intermediate orange. On a side note- females are always larger than males in both species.
As a new birdwatcher, I learned that the first field mark to look for is shape of the tail. Cooper’s have a longer tail with a rounded edge and Sharp-shin tails have a squared off, blunt look, regardless of age. The tail difference is easiest to see when a bird is airborne and backlit, but not always obvious if you are lucky to find a perched hawk.
With experience, I’ve discovered another constant field mark on adults, which I now check for right away. Cooper’s Hawks have a pale nape so that the viewer sees a colour gap between the gray cap and back feathers. The gray on an adult Sharpie continues up and over from the forehead right down to the back. You’ll also notice that a Sharpie’s head is small and rounded and the whole body is more compact. Cooper’s have more of a flattened look to the top of the head, sometimes showing a tiny bit of crest extension or “hackle” on the back edge if alarmed. The whole body and tail of a Cooper’s Hawk appears elongated. Look for body shape and size to compare immature birds in flight. See how far the head projects beyond the wings. From below with binoculars, you’ll see a mess of vertical streaks on the breast, horizontal lines on the underwings and several wide tail bands.
Finally, Sharp-shinned Hawk eyes are larger in proportion to their head and positioned closer to the bill. The roundness gives them a “bug-eyed” look. If I had to assign a look to the Cooper’s it would be fierce and almost angry. Yes, like an angry bird with a “don’t mess with me” vibe. Humans do like to personify birds, don’t they!
Don’t feel badly if you still haven’t figured out who’s who in the hawk world. It requires lots of practice and time observing in the field. There is an entry line on eBird data forms for accipiter or hawk sp., meaning general species, so don’t be afraid to use it. Not all birds can be successfully identified. Some birders find support by joining others down at Port Stanley’s TTLT lands (Hawk Cliff) for a group hawkwatch during migration. Share the awesome spectacle with other like-minded enthusiasts!
**photos from top - adult Sharp-shin perched, juvenile Cooper's and Sharpie in flight (compare head extension and tail shape), adult Sharp-shin, sub-adult female Cooper's and juvenile Sharpie with captured goldfinch