How To Identify Birds From Their Size and Shape

Birds come in different sizes, shapes and plumages, which can make identification challenging. Each characteristic of a bird can lead, or point, to a correct identification. Using size and shape is extremely helpful when identifying a bird and should be one of the first features inspected when attempting identification. Critically studying every bird, especially structure, bill, and tail shape, is the best way to learn distinct bird silhouettes. After studying bird size and shape, you will be able to differentiate between Red-winged Blackbirds and Common Grackles, even if you only get looks at backlit birds!
1. Learning More about Silhouettes

turkey vulture

Generally, you do not need to see plumage characteristics to narrow down a species’ identification. A bird’s silhouette can quickly allow you to get a good sense of bird’s size and structure. Therefore allowing you to quickly rule out other bird families, even those similar in size. For example, learning wing shape of birds in flight can facilitate identification. Turkey and Black Vultures are roughly the same size and can almost always be seen in the same kettle. Learning their silhouette can help separate the two. Take a look at the photo of a Turkey Vulture below. Notice the long, broad wings, and relatively long tail. Turkey Vultures fly with their wings in a dihedral and consistently rock back-and-forth in flight. Black Vultures also have rounded wings, but have a short, rounded tail.

Turkey Vulture – Photo by Tim Schreckengost

2. Compare size against the birds that you know quite well

Judging the size of a bird can be extremely difficult, especially if there is nothing near it for reference. Size can be deceiving and can always be tricky to judge due to distance and behavior.
Judging size is easier if the bird in question is near a bird you’ve studied extensively in the past. For instance if you can say a bird is smaller than an American Robin, but larger than a Black-capped Chickadee, the list of possible species will lessen significantly. Size, along with other characteristics, is especially beneficial when differentiation between Hairy and Downy Woodpeckers. If you look at the photo below, you can see the small, thin bill, small head, and relatively short tail. Hairy Woodpeckers are longer overall, have a thicker, longer bill, and a bigger head.

Downy Woodpecker – Digibinned with a Samsung Galaxy S4 + Celestron Granite 8x42 Binoculars & Phone Skope Adapter. Photo by Tim Schreckengost.

downy wood pecker

3. Compare against birds in similar field of view

Finally, if you are attempting to narrow down an identification based on size, birds should be the same distance from you and in the same field of view. This will give you a better understanding of height, length, and overall size of the bird in question. When you discover a mixed species flock, you can use the birds that you previously studied to help identify the individuals that are giving you trouble.