I hope you’ve settled in for a good season of birding. June is when most birds fall right into your lap, singing, wooing, defending territories and generally strutting their stuff. They are in their brightest colors.
Normally, I might discuss the importance of color and field marks, but instead of identifying birds, let’s assemble one.
Every color, every field mark, is there for a reason. Every bird needs to move, reproduce, eat and avoid being eaten. Any species that failed even one of these requirements went extinct long ago.
Take eating. How would you design a bird to crack seeds? Of course, you’d do it the same way you crack walnuts, with a bill heavy enough to break the shell.
How would you design a bird to catch flying insects? Of course, with a thinner but longer bill that can snatch a moth out of the air in the same way you might grasp a morsel with chopsticks. Just by the bill, you can perhaps tell the difference between a finch and a flycatcher.
What about birds that eat both bugs and seeds? Well, duh. Their bill is dual purpose. A chickadee’s bill is heavy enough to open a sunflower seed, and nimble enough to glean a spider from tree bark, but not useful for grabbing an insect out of the air. A robin’s bill is designed to pluck berries and probe for shallow worms, but it would need the longer bill of an American woodcock to probe for deeper worms.
A chimney swift spends much of its life in the air. Its legs are tiny, barely there, because chimney swifts never walk and only rarely perch. Longer legs would only make it less maneuverable while airborne, chasing after its diet of flying insects and moths.
On the other hand, let’s say you wanted to design a bird that feeds both on land and in the water. You would give it long legs for wading, and also a long bill and a long neck for reaching the ground, right? You’d design a heron.
Let’s discuss courtship next. How would you design a bird that needs to visually attract a mate? Bright colors like a cardinal? Bold patterns like a black-and-white warbler? It would be dangerous to put bright colors on a bird that must stay hidden in daylight, so all our nocturnal species are drab and mottled.
However, if you don’t have colorful feathers to entice the ladies, how do you attract a mate? Voice is one way. Owls, woodcocks and whip-poor-wills are famous for their nocturnal calls.
Displays are another. Nighthawks, woodcocks and Wilson’s snipe put on impressive aerial flights at night, making weird sounds all the way. Sexy.
Let’s assemble a hummingbird. It needs to hover, and even fly backward, so the wings must beat quickly and rotate as needed. Most importantly, it needs a bill designed to feed on flower nectar.
In eastern North America, the ruby-throated hummingbird can reach into most blossoms native to this part of the continent. But out west and in the tropics, the flowers vary wildly. So do the specialized bill shapes for multiple hummingbird species that feed on them. The deeper the blossom, the longer the bill.
Let’s make a fish-eater, one that can dive into the water to snatch dinner. It needs a bill long enough to get a good grip on its slippery, wriggly prey, but not so long that it’s unwieldy.
It must be able to wait and watch for fish to approach the surface, so circling or hovering is a must. The wings must be long enough to hover, but short enough to allow takeoff from the water without drag. Voila, we’ve created a belted kingfisher. Or a tern. Or, if the bird catches fish in its talons instead of its bill, we’ve created an osprey.
Many other field marks on birds turn out to be functional. Cardinals, jays and titmice have crests that are more than ornamental. They use them to communicate with each other.
Red-winged blackbirds use their red patches to signal aggression and territorial defense. The crown on a ruby-crowned kinglet or golden-crowned kinglet is usually hard to see, unless the bird is agitated. Then it pops up in a blaze of angry color. Ovenbirds have similar orange crowns, but rarely raise them except to defend their nesting territories from other male ovenbirds.
Every bird is assembled from just the right spare parts needed to eat, prey and love.
