Who’s Kenn? Merely put, Kenn is a nationwide treasure. A famend birder, writer, and conservationist, Kenn Kaufman has spent his life devoted to observing birds, studying about birds, writing about birds, and sharing the world of birds with others. With all that birdy data in his mind, he additionally acts as the sector editor for Audubon journal. So, every time we have now a hen query stumping us across the workplace, we simply ask Kenn. And now you’ll be able to, too! When you’ve got a hen or birding query you want Kenn to reply, depart them within the feedback on Fb or ship us an e-mail. Possibly subsequent month you will get the form of thorough, considerate, and even humorous response from Kenn we have grown so keen on through the years. —The Editors
Query: We noticed a really dark-colored Purple-tailed Hawk on a subject journey. One individual referred to as it a darkish part, however one other referred to as it a darkish morph. Which is right?
Kenn Kaufman: No two birds look precisely alike. This reality could make birding extra fascinating and, generally, extra irritating. Figuring out them can be simpler if each particular person of a species matched all of the others of its sort, however in actuality there are a lot of sorts of variations.
Particular person variation happens in each species. At a look, every hen in a flock might sound equivalent, however if you look extra intently, you see delicate variations. Examine a winter flock of American Robins, and also you’ll see how the whole lot about them varies: the shade of rufous on the chest and grey on the again, the tone of yellow on the invoice, the quantity of streaking on the throat, the shapes of the white spots across the eyes and on the corners of the tail. Even birds in a single stable coloration, like American Crows, present variations in form and dimension in the event you maintain and measure them. (However I don’t suggest that, so you will have to take my phrase for it.)
If we zoom out from the person degree, we are able to additionally see bigger classes of variation. Many species present regional variations. These may be apparent: within the Northern Flicker, for instance, the populations within the East have vivid yellow wing-linings, whereas these of the West have salmon-pink. Darkish-eyed Juncos breeding in numerous areas of North America put on distinctly completely different coloration patterns, with the “Oregon” Juncos of the Northwest bearing brown and reddish hues not like the “Slate-colored” Juncos of the East, though they’re all a part of the identical species. And in lots of birds, after all, men and women look completely different.
Most species additionally present some variations between juveniles and adults, and in some the age variations are excessive; Herring Gulls change look virtually consistently for the primary 4 years of life, with many immature phases between the dusky brown of juveniles and the grey and white plumage of adults. There are seasonal variations, too, as when male American Goldfinches molt from the delicate buff tones of winter to good yellow in spring, after which return to buff once more in fall. Even species that molt solely yearly will present gradual change, with colours starting to fade and edges of wing bars carrying away as time for the subsequent molt approaches.
However a very completely different form of variation includes these species which have distinct coloration morphs. In these circumstances, the variants should not the results of geography because the completely different morphs reside facet by facet. Nor are they attributable to age, intercourse, or season. As a substitute, a major share of the grownup members of the species put on a unique coloration sample from others, and it’s a everlasting situation. A species with distinct coloration morphs is alleged to be polymorphic.
Some examples are placing. Within the Snow Goose, for instance, adults are white with black wingtips—or largely darkish blue-gray, with white heads. The darkish kind was thought of a separate species, referred to as “Blue Goose,” till 1973; however the two types barely differ genetically, they’ll mate with one another, and a pair of “Blue” Snow Geese might have some white offspring in addition to darkish ones. Regardless of their completely different appears to be like, they’re simply coloration types of the identical species.
One other instance includes the Japanese Screech-Owl. Most people are grey with intricate black markings, however some are vivid reddish brown with decreased markings. (And a few others are an intermediate gray-brown.) Total, the “purple” birds make up roughly one-third of the inhabitants.
After which there’s that seasonally applicable polymorphic hen, the Wild Turkey. As described in an Audubon story a few years in the past, about 1 in each 100 turkeys is an instance of the “smoke” morph, with the same old reddish brown physique coloration changed by pale smoky grey. Domesticated turkeys can range in coloration, after all (as is true of many domesticated birds), however the smoke morph happens naturally within the Wild Turkey inhabitants.
For some polymorphic species, there’s a geographic pattern to the place the completely different morphs are commonest. Within the Snow Goose, the blue morphs are most plentiful within the central inhabitants that spends the winter close to the Gulf Coast. Amongst Japanese Screech-Owls, the purple morphs are commonest in heat, moist climates—making up greater than half the inhabitants in elements of the South—and scarce in dry climates, akin to close to the western fringe of their vary on the Nice Plains.
One other instance of geographic bias is notable in Purple-tailed Hawks. Within the japanese United States and Canada, virtually all of the Purple-tails are of the pale morph, with white chest and darkish belly-band. However within the West, many happen in darkish or rufous morphs, with the underparts very darkish brown or heat reddish brown. (There are different western variations, just like the darkish “Harlan’s” subspecies in Alaska and the mysterious pale “Krider’s” Purple-tail on the northern prairies, however discussing all these would take up a complete column.) For no matter motive, North American birds of prey present extra variation within the West than within the East. Swainson’s Hawk and Ferruginous Hawk, discovered from the Nice Plains westward, each have pretty frequent darkish morphs along with their typical patterns. The Broad-winged Hawk, largely an japanese hen, virtually by no means happens in a darkish morph—besides on the northwestern fringe of its breeding vary, in western Canada.
There are additionally fascinating geographic developments in the place the colour morphs of some seabirds are discovered. Parasitic and Pomarine Jaegers nest on Arctic tundra and winter at sea, and so they happen in pale and darkish morphs, in addition to some intermediates. In Parasitic Jaegers, the darkish morph is extra frequent in southern elements of the breeding vary, akin to southern Alaska and central Canada, whereas the pale birds predominate within the excessive Arctic. In Pomarine Jaegers, then again, no such geographic pattern has been confirmed. The Northern Fulmar, breeding in island colonies at excessive latitudes, additionally has each pale and darkish morphs. Within the North Atlantic the birds are virtually the entire pale morph besides on the northernmost colonies, the place many are darkish. Within the North Pacific, oddly sufficient, the sample is reversed, with largely pale fulmars on the northernmost colonies and the darkish morph concentrated farther south. These various patterns of prevalence are puzzling for scientists who’ve tried to elucidate why such polymorphism develops within the first place.
As you will have seen, up to now I’ve largely talked about birds of prey and water birds. Solely about 3.5 p.c of the hen species on this planet are polymorphic, and only a few of those are songbirds. Nevertheless, we do have one quite common instance in North America. Grownup White-throated Sparrows happen in two coloration morphs, with head stripes of both tan or white; behavioral variations between these types have been studied for years, offering no finish of surprises.
You additionally might have seen that I’ve simply been speaking about examples and haven’t answered the unique query: Is it right to refer to those coloration types as phases or morphs? I’ve been hinting on the reply, although, by calling them morphs. The time period “part” signifies one thing that adjustments over time, just like the phases of the moon. An avian instance would contain Little Blue Heron. In that species, juvenile plumage is white and grownup plumage is darkish slate-blue. In between, after they’ve partly molted, their patchy dark-and-white sample is commonly referred to as the “calico part.” That’s a part, and it will be improper to name it a morph—it’s non permanent, not everlasting.
So, when somebody is happy to inform me they only noticed a “purple part screech owl,” do I right them? No. I do know completely properly what they imply, and I’m happy they even know that this owl has completely different coloration types. In the event that they ask me about terminology I’ll clarify that what they noticed was a morph, not a part. However except they ask, I’ll simply be a part of them in celebrating the joy of seeing these intriguing variations in nature.