Ask Kenn Kaufman: Falcons, Hawks, Owls, Vultures—What Exactly Is a Raptor?

Who's Kenn? Simply put, Kenn is a national treasure. A renowned birder, author, and conservationist, Kenn Kaufman has spent his life dedicated to observing birds, reading about birds, writing about birds, and sharing the world of birds with others. With all that birdy knowledge in his brain, he also acts as the field editor for Audubon magazine. So, whenever we have a bird question stumping us around the office, we just ask Kenn. And now you can, too! If you have a bird or birding question you'd like Kenn to answer, leave them in the comments below or on Facebook. Maybe next month you'll get the kind of thorough, thoughtful, and even humorous response from Kenn we've grown so fond of over the years. —The Editors 

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Q: I recently learned that falcons and hawks aren’t close relatives, but they are both considered raptors. That made me wonder: What exactly makes a bird a raptor? And why are vultures, who scavenge instead of hunting, also considered raptors?

KK: What is a raptor? That question has proven surprisingly hard to answer. Even though many people and organizations all over the world are focused on raptor research and rehabilitation, there has been no universal agreement on exactly which birds should be included under that term.

It’s important to start by understanding that this is not strictly a category of close relatives. The word “raptor” is based on Latin words referring to seizing or plundering, so definitions have focused on the grasping, raptorial feet of hawks or owls as a defining characteristic. We have long understood that owls are not related to hawks, but they’re usually considered to be raptors anyway because they have such clearly predatory lifestyles. Presumably the same would apply to falcons. We now know that these supreme aerial hunters are related more closely to parrots than to hawks—some people have even dubbed them “murder parrots”—but I doubt anyone would seriously say falcons don’t count as raptors.

Now, this line of thinking leaves the vultures out in the cold, since these scavengers have relatively weak feet, not suited to grasping prey. At the same time, it would be awkward to exclude them, because Old World vultures belong to the same family as the typical hawks and eagles. Further complicating things, New World vultures, even though they’re very similar, are classified in a different family, and currently even placed in a different order. It would seem odd to say that some vultures are raptors and others are not.

And what about other predatory birds? Some people have suggested that shrikes should be included, since these songbirds have hooked bills and they regularly prey on rodents and small birds. But if we stop to think about it, a robin killing and eating an earthworm is a predator, too, isn’t it? Just with smaller prey. So is a chickadee eating a caterpillar or a gnatcatcher catching a gnat. If we expand the list of raptors to take those in, the category would include most birds of the world and the term would lose any useful meaning.

So what is a raptor? That’s a matter of opinion. Fortunately I don’t have to just give my own opinion, because some top authorities have just weighed in on the question.

In the December 2019 issue of The Journal of Raptor Research, eight experts proposed a new definition. Christopher J.W. McClure and his colleagues looked at recent advances in the high-level classification of birds to find a grouping that uses actual relationships. Detailed DNA studies published since 2008 have suggested that most landbird groups evolved from ancient common ancestors that were predatory in nature. With that as a starting point, McClure and coauthors define raptors as “all species within orders that evolved from a raptorial landbird lineage and in which most species maintained their raptorial lifestyle as derived from their common ancestor.”

In practical terms, the definition would exclude most orders of birds and would apply only to these orders: Accipitriformes (hawks, eagles, etc.), Strigiformes (owls), Cathartiformes (New World vultures), Falconiformes (falcons and caracaras), and Cariamiformes (seriemas).

The latter group may be unfamiliar to many readers. Seriemas are large, long-legged birds that run on the ground in open country in South America, preying on reptiles, rodents, small birds, and large insects. Superficially they might suggest the Secretarybird, a ground-dwelling, long-legged predator from Africa, which occupies its own family within the Accipitriformes. Seriemas and the Secretarybird are not related—except for the fact that, under this new definition, both are regarded as raptors.

Since the definition was just published days ago, I don’t know if it will gain universal acceptance. But it makes a lot of sense to me and works well for the time being.

Q: Why do certain kinds of birds gather in the evening to sleep in big communal roosts? Is it just to stay warm? 

KK: It’s a familiar sight on winter evenings: flocks of birds overhead in fast, purposeful flight, all going the same direction. These flights may involve blackbirds, or starlings, or crows, or various other species, but they all represent the same thing: large numbers of birds gathering with others of their own kind to sleep for the night in what’s called a communal roost. 

A common assumption is that they gather for warmth, and in some cases that is true. A dozen or more bluebirds may gather at night in one tree hole or nest box. In mountain forests of the West, multiple flocks of Pygmy Nuthatches may gather to sleep in the same tree cavity on the coldest nights. But for species that perch on open branches to sleep, like blackbirds or crows, temperature regulation doesn’t seem to be a main factor. When these birds fly many miles, converging from all over a wide area, to spend the night in a central roost, they seem to do it for other reasons.

Finding the roosting sites by following these evening flights can be an intriguing challenge. Typically they’re in sheltered places. Thousands of blackbirds (or even hundreds of thousands) may choose a brushy marsh surrounded by water. Hundreds of crows may roost together in a dense stand of tall trees. In the Southwest, large numbers of Great-tailed Grackles may fly for miles from the open countryside to the centers of towns and cities, establishing noisy roosts in trees in parks or along city streets. All of these places may offer some degree of protection from predators, but to get there, the gathering flocks may have flown past numerous other spots that could have been equally safe. So there’s more to it than just seeking shelter.

In these cases, when flocks of birds fly in from miles around, the communal roost may serve in a more surprising role: as an information center.

Consider a species like Red-winged Blackbird. In winter, flocks of Red-wings wander for many miles through open country and farmland, looking for feeding opportunities that may vary from week to week. With short daylight hours and long, cold hours of darkness, they need to focus on finding enough food each day to sustain them through the nights. If some birds succeed in finding a good food source one day, they’re likely to return to the same spot the next day. On the other hand, birds that had poor success one day may stick around the roost in the morning, waiting to see which direction the smart kids will go. They’ll follow the flocks that set out in a purposeful return to good feeding grounds. In this way, even without language, the Red-wings can share information that’s useful for survival.

This kind of dynamic probably applies to most species that use communal roosts in the non-breeding season, especially those birds that range over wide areas in the daytime. These can include swallows that feed on concentrations of flying insects, vultures that feed at large carcasses, gulls that scavenge where some kind of waste has been dumped—all are going for food sources that may be temporary and patchy, so it’s useful to know where others have had recent success. By coming together every night and then watching their fellows depart in the morning, they can tune in to the latest developments. These big communal roosts are often spectacles for observers, but they also show us an amazing example of communication among birds.    

Q: Why are ducks always assumed to say “quack” when most wild ducks don’t make a sound anything like that?  

KK: You’re right, duck voices are more interesting than they’re usually quacked up to be. (Sorry.)

Seriously, though, some ducks have wonderful voices. Years ago at Churchill, Manitoba, friends and I were standing at the tip of Cape Merry, looking out over Hudson Bay on a calm June evening, when a flock of male Black Scoters began calling from the waters below us. Long, clear, ringing whistles, with almost a minor-key quality, it was one of the most beautiful bird sounds I’d ever heard. I’ve had greater respect for ducks as vocalists ever since.

One thing that’s notable among ducks is that males and females typically have very different voices. For example, in American Wigeons, the male gives a far-carrying three-noted whistle, whee-WHEEW-wheew, with the second note highest and loudest. The female’s usual calls are low errr or grrr notes. Among Wood Ducks, the male gives a thin djeee or ji-jib while the female’s most common call is a louder, shrill oowheak!

Many of the sea ducks are relatively quiet. Surf Scoter males make gurgling and croaking notes during courtship displays, while females have some short nasal sounds. Male Spectacled Eiders may make soft cooing notes, and females use some croaking and clucking notes to communicate with their young. On the other hand, Long-tailed Duck, another Arctic-nesting sea duck, is one of the most vocal members of the family. Flocks in late winter may ring with the yodeling yow-owdle-ow of the males, audible from almost a mile away.

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The pinnacle of quackiness is the voice of the female Mallard. 

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Females of many dabbling ducks (but not males) do make noises sounding very much like quack. The male Green-winged Teal does a squeaky chyerk while the male Blue-winged Teal gives a high, peeping whistle; females of both species make quacking sounds. Among Northern Shovelers, Gadwalls, Northern Pintails, and other dabblers, the voices of males are all over the map, but the females make calls that could be written as quack.

The pinnacle of quackiness is the voice of the female Mallard. While males mostly give variations on a thin rreeb, the female delivers a loud, descending QUACK, Quak qua-qua-quack! It sounds exactly like the familiar barnyard duck. And that’s no coincidence, because the familiar barnyard duck actually IS a Mallard—a domesticated version of the species. Almost all domestic ducks are descended from either the Muscovy Duck (of the American tropics) or the Mallard, and the latter type is far more numerous. Even though Mallards have been domesticated for thousands of years, they still sound essentially identical to their wild ancestors.

So it’s the female Mallard—common in the wild over much of the northern hemisphere, common in domestication over much of the world—that’s the prototypical quacker. We should all salute this bird for its impact on the English language, and the next time you're out in the field, make sure you pay extra attention to the rich and varied repertoire that ducks add to the sounds of the outdoors.  

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Have a bird or birding question for Kenn? Leave it in the comments below, and maybe he'll answer it in a future column.