With over 800 species of birds in North America alone, it's helpful to narrow the choices down from the get-go. Scientists use dozens of different families to group avians: It pays to learn which traits define each family. Hone it down to the family level, or to a group of families, and you’ll be halfway home on the final ID. You'll even learn the subgroups in each family as you go along.
Even among closely related birds, practically no two species share the same exact shape. Even when you’ve identified a bird by some other means, it’s a good idea to spend an extra minute studying its shape so you can recognize it in the future. If you can view a mystery bird in direct comparison to one that you recognize, it’s good to note whether the bird is a little smaller than a robin, larger than a coot, and so on.
It’s also good to get into the habit of looking for certain kinds of markings. Does the bird have a white ring around the eye, or a pale stripe above it? Is the body marked with round spots, lengthwise stripes, or crosswise bars? Does the target have white outer tail feathers? These “trademarks of nature” often will pin down the species for you.
Sometime we become so captivated by a bird’s good looks that we fail to notice what it’s actually doing. Is the bird hopping on the ground, climbing a tree trunk, wading in water, or flitting in the treetops? If it’s climbing a tree, is it hopping up like a woodpecker, creeping along the bark like a Brown Creeper, or scuttling upside down like a nuthatch? Is the bird all alone, or part of a flock? These behaviors can all point to its identity. If your mystery bird is making some distinct sound, it’s worthwhile to try to make a note of it.
Birds are also surprisingly predictable when it comes to timing—for many it's a matter of life or death. Local books or checklists can tell you about the seasonal occurrence of species in your area. For example, in much of the northern United States, the easiest way to tell two rusty-capped sparrows apart is to glance at the calendar: Chipping Sparrow if it's summer, American Tree Sparrow if it's winter.
Creatures on wings are highly mobile, and can wander outside of their typical habitats, especially during migration. But most of the time, habitat is an excellent clue. You might see a Horned Lark on the ground in a plowed field and a Red-eyed Vireo in a forest treetop, but you’re very unlikely to see them trade places.