Well, it’s that time of year again. No, I’m not talking about shopping for holiday gifts or making New Year’s resolutions. I refer to that one day each year, the Christmas Bird Count, when you’re supposed to identify every crow that you see. The whole point of the Christmas Bird Count, after all, is to keep tabs on ever-changing bird populations, and that includes populations of crows. What should you do about this problem? One option is to ask your local CBC compiler for a territory without crows! A more practical solution might be to go with someone who’s good at telling them apart. A third option (and my personal preference) is to learn how to ID crows yourself.
Both crow species are common in Cape May but their status varies through the year. American Crows are a bit more numerous in winter from about October to March. Fish Crows, on the other hand, are commonest in summer and scarcer in winter. Peak migratory movements of Fish Crows can be seen in late March and April and again in October and November. Despite being less common in winter, like American Crows, Fish Crows form large winter roosts where they can be seen by the hundreds, so one should never assume that all winter crows are Americans.
To approach the crow identification problem, you should begin at the same place you begin all bird identifications: size, structure, behavior, and voice.
Size
Fish Crows are about 20-25% smaller than American Crows, a difference that is obvious when the two are side-by-side. Of course size is more difficult to judge on lone birds, but with practice it can be useful even then.
Structure
Structural differences between the two crow species are subtle to say the least. In fact, in many poses the two species may look essentially the same (…and you wondered why crow ID is so difficult!). However, there are real differences that are usually perceptible and sometimes obvious. Let’s first consider standing or perched birds. Compared to American Crow, Fish Crow is slimmer overall with a smaller head and bill, longer, slimmer tail, longer wings, and shorter legs. On active birds that are walking around, these differences are not at all obvious. However, when relaxed, perched Fish Crows assume a particularly distinctive pose as they tend to pull their necks into their shoulders, reducing the apparent size of their heads and making the rear quarters look distinctively attenuated. In this relaxed pose, Fish Crows also tend to show steeper foreheads and puffier throats than Americans (features that accentuate the small bill) and they also tend to fluff up their body feathers, making their short legs almost disappear (recalling Arctic Tern with its belly practically touching the ground).
In flight, some of thee same features are also apparent. In particular, Fish Crow’s relatively longer, slimmer tail is often distinctive. Wing shape and pose can also be helpful. Though wing shape may appear nearly identical at times, Fish Crows have slightly more tapered wings that sometimes take on a distinctively pointed shape. Americans have slightly broader, less tapered wings and blunter wing tips. One subtle feature that is sometimes helpful has to do with the primary “fingers”. On American Crow, the innermost “finger” (primary #5) is slightly longer and projects out past the trailing edge of the wing during normal flight. On Fish Crow, this primary is shorter so no fingers appear to project out past the trailing edge. The resulting impression is of fewer fingers and a more clean-cut trailing edge on Fish Crow. This difference is much less apparent when the wings are fully outstretched and may be obscured on molting birds. [Note that this feature should not be confused with the whole hand projecting past the secondaries, a feature that both species show on every upstroke.]
Behavior
Behavioral clues are surprisingly helpful in distinguishing our two crow species. Habitat is the first clue. Fish Crows are much more at home in suburban habitats than Americans. They regularly forage around shopping centers where they raid dumpsters and search for unwanted French fries. Americans are much more rural and tend to forage in open farm country or along highway roadsides where they look for roadkills. Both species may be found at landfills. Fish Crows are also more gregarious than Americans. Though both species may form huge winter roosts, Fish Crows tend to form bigger, more tightly spaced flocks during their daily foraging rounds. Americans usually form smaller, more widely spaced flocks. (But they may be more tightly spaced when harassing a raptor!) Mixed-species crow flocks may sometimes be found as well. Another useful behavior has to do with telephone wires. Both species perch on them but Fish Crows regularly do so in large, shoulder-to-shoulder flocks. Americans usually do so singly, not in flocks. Flight style of the two species is very similar with much overlap, but Fish Crows tend to have deeper, stiffer, quicker wing strokes than Americans.
Voice
The field mark that trumps them all with crows is voice. Voice is by far the most reliable means of separating Fish and American Crows and waiting to hear a crow call to confirm an identification is a great way to learn the other field marks. American Crow’s typical call is a loud, ruckus series of cAAw notes. Although there is much variation in this call, it always has a distinctively aggressive or angry quality. Fish Crow gives two main call types including a nasal, one or two-note ahh or ca-hah, and a more rolling, liquid series of cahh notes. The latter call is similar in pattern to American Crow but is much softer and more nasal. Juveniles of both species give a drawn-out waaah and other variations but the quality is more nasal in Fish Crow.
Molt
Although it will not help you on a Christmas Count, the timing of primary molt differs between Fish and American Crows and can be a helpful distinction between them during summer and fall. A bird in primary molt will show ragged-looking wings with short or missing feathers, creating obvious gaps. The timing of primary molt is related to the nesting season, beginning after the young have fledged. Nesting seasons, and the corresponding molt schedules, vary regionally. Here in southern New Jersey, American Crows molt their primaries from about late May to late July or early August. Fish Crows, which nest later than Americans, begin primary molt in early July (exceptionally late June) and finish in mid-late October. If you hang out on the Cape May hawkwatch platform in September or October and see a crow with ragged wings, it will be a Fish Crow.
As a final note, it should be emphasized that telling crows apart can be very, very difficult. There’s nothing wrong with leaving a bird unidentified, even on a CBC!
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Photo 1 – Fish Crows and Rock Pigeons, August, Connecticut. Fish Crows are much more gregarious than American Crows, traveling in tight flocks and often perching shoulder-to-shoulder on wires. When American Crows perch on wires, they usually do so singly. Notice that these crows are scarcely larger than pigeons and have a slim, attenuated shape. |
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Photo 2 –American Crows, October, New Jersey. American Crows travel in smaller, looser flocks than Fish Crows and prefer more rural habitats. Notice the bulkier head, bill, and body and less attenuated shape than Fish Crow. |
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Photo 3 –American Crow (left), October, New Jersey, and Fish Crow, September, New Jersey. Fish Crows are slimmer overall than Americans, with slightly longer, slimmer tails. The Fish Crow’s wings are slightly more tapered, and often appear less “fingered”. In this gliding pose, notice the American Crow’s innermost “finger” (primary #5) projecting out past the trailing edge of the wing. On a Fish Crow, this feather is shorter, making the trailing edge more even without a projecting finger. |
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Photo 4 –American Crow (left), October, New Jersey, and Fish Crow, September, New Jersey. Shapes of these two species never appear more similar than in this wheeling pose. The Fish Crow’s relatively smaller head and longer, slimmer tail are somewhat evident, as is the less fingered appearance. |
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Photo 5 –American Crow (left) and Fish Crow, October, New Jersey. In direct flight, Fish Crows often take on a distinctively pointed wing shape with a straight trailing edge and only a few visible fingers. In comparison, the American Crow shows a blunter wing tip with more prominent fingers, the innermost projecting past the trailing edge. In this pose, the Fish Crow’s relatively smaller head and longer tail are also evident. (Photos by Michael O'Brien.) |
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