Birdist Rule #57: It’s Summer—Watch Out for Juveniles!

Pretty soon this summer you might see a bird that you don’t recognize. It might look sort of like something you know, but . . . something’s just off. It doesn’t match anything in your field guide. What could it be?

Before you go and call the local university thinking you’ve found a species new to science, consider whether it’s a recently fledged bird. There’s a sweet spot in the middle of summer when these birds have left their nests but aren’t yet sporting full adult plumage. This interim plumage is called “juvenal” and applies to birds in their—you guessed it—juvenile phase. Like human teenagers, these birds are an odd-looking, awkward version of what they’ll soon become. We’ve all been there.

Birds in this juvenal plumage can be very difficult to identify in the field, but it’s worth trying, and you’ll learn some important things about the development of young birds in the process.

Let’s start with a quick lesson about the stages of bird development. First, birds start as eggs. Did you know that? I really hope you did. Let’s continue.

Next, baby birds hatch out of eggs and become hatchlings. Some hatchlings are born into the nest completely defenseless, usually unfeathered and with their eyes closed. Others, such as plovers, quails, and other birds born in open country, are born with feathers and can run or swim (not fly) right away. This is to help them avoid predators.

Species that continue to develop in the nest are called nestlings (noticing a theme here?), and these birds hang out and wait for their parents to bring them food. As they grow and gain strength, they also shed their downy feathers for new feathers that allow them to fly. Once that happens and they’re ready to leave the nest, our nestlings become fledglings. Different species fledge at different times, but most songbirds and smaller species fledge from late June through July. So if you’re doing any birding during those months, be prepared to see some juvenile birds.

Out of the nest, fledglings are, obviously, much easier for the average birder to see than nestlings. It’s important to note here that fledgling birds can look pretty pathetic, and may even appear to be in trouble if you see them flapping around on the ground. However, as the ever-helpful Rosemary Mosco of Bird and Moon illustrates in her instructive Found a Baby Bird? comic, you should leave fledglings alone unless they’re in immediate danger; this is a natural step and the birds are usually in close proximity to their parents.

So, instead of trying to offer misguided help to a fledgling bird, maybe just go ahead and try to figure out what species it is.

Bob Mulvihill banded thousands of birds during his time at the Powdermill Avian Research Center in western Pennsylvania, which is the longest running year-round bird-banding station in the country. He’s handled birds in just about every conceivable plumage and knows firsthand how much of a challenge it can be to identify juvenile birds.

"Some juvenile species are fairly easy to identify, like American Robins, which just have brown spots over a reddish breast,” says Mulvihill, who is now an ornithologist at the National Aviary in Pittsburgh. “But others are like ‘huh?’” He rattles off some of the classic challenges: Dark-eyed Juncos and Eastern Towhees are streaky and bland; adolescent Common Yellowthroats can look like Mourning Warblers; and young Swamp, Song, and Lincoln’s Sparrows are nearly inseparable, even in the hand. Mulvihill pointed me to one particularly difficult juvenile ID he had back in 2002 (halfway down the page here). It’s a Yellow Warbler, though I wouldn’t have guessed it.

Most field guides will include images of immature birds, but according to Mulvihill, there isn’t really any one good field guide for juvenal plumages. He does recommend Julie Zickefoose’s Baby Birds book for reference, though it’s not really a field guide. There is also a pretty good collection of reference pictures on the Powdermill website. Look at that tiny hot mess of a Gray Catbird!

If you scan the Powdermill site, you’ll notice how some of those juvenile species look more like adults than others. The Black-and-white Warbler and the Louisiana Waterthrush, for example, are pretty recognizable, while the Common Yellowthroat and Black-throated Green Warbler are distinctly different. Mulvihill says that camouflage is a big part of it; juvenile open-country birds such as shorebirds are often cryptically patterned in order to make them more difficult to see, and a songbird’s juvenile blandness helps it blend into its surroundings.

What’s more, “it’s expensive to produce fancy feathers,” Mulvihill says. Young birds would would have to expend energy to create bright, multi-colored plumages—energy that is badly needed to develop into an adult.

How can you tell if a weird bird you’re seeing is a juvenile? There are some clues. Juvenile birds are fluffier looking, as they’re replacing their down feathers with adult ones. Look again at those photos on the Powdermill website. See how scruffy those birds are? Cute, I know, but also a good sign that you’re not looking at a put-together adult.

Proportions can also help. Younger birds often have bills that look too big for their head, and short-looking, stubby feathers. The body can just look sort of “off” as the bird grows into itself. Colorful or fleshy areas at the corners of the mouth—called the “gape flange”—might be visible remnants of the bird’s recent days as a wide-mouthed, begging nestling.

Finally, though it sounds silly, the bird just might be acting young: begging and whining, not very steady on its feet, and generally dopey. Instead of gracefully flitting through the branches, the bird might just be slowly moving from one to another. Sometimes they’ll just sit there looking kind of dazed. If it’s not acting like a typical adult bird, there's a chance you've got a juvenile.   

Getting good looks at these young birds is much more difficult without the benefit of a mist net and banding equipment. So, Mulvihill’s best advice for trying to identify these birds is to just wait. “Most often when you see a juvenile bird, the adult bird will return or show itself within 60 seconds,” he says. Though they’ve fledged, juvenile birds stick close to their parents, who will still feed them and try to keep them out of danger.

Thankfully for confused summer birders (and for hard-working bird parents), fledglings don’t stay long in their awkward phase. Juvenal plumages in songbirds generally last less than four weeks, after which bird begins molting into a first-year plumage that often looks nearly identical to adults of the same species. So, enjoy this fleeting moment of avian adolescence while it lasts. By fall, these birds will have to tackle the very grown-up business of migration.