Photo © Al Tuttle

Identifying Nests and Eggs

So you found an unidentified nest, and want to know what bird it belongs to? With a little detective work, you can determine whose nest or eggs you found.

Where to start:

  • Three Nests
    Three Nests

    Can you identify which 3 species have previously used this box? (Answer located at the bottom of this page.)

    If the nest is active, watch from a safe distance with binoculars to see if any birds approach the nest. Female birds can be hard to identify, so if you’re not sure what species it is, write down a careful description and use a regional field guide to identify the species.
    Tip: Don’t have a field guide? Browse by shape in our online bird guide
  • Location and timing are key! Migratory birds have separate ranges for their breeding and wintering activities, whereas “resident” birds live in the same region year-round. Nests found early in the spring tend to belong to non-migratory residents, while migrants return and breed later in the spring and summer. For example, you can expect to find a chickadee nest earlier in the spring than a warbler nest. However, there are always exceptions such as the American Goldfinch, which tends to nest during the late summer despite being a year-round resident. Birds in the southern states also tend to nest earlier than birds in northern regions. Use your location and the timing of the nest to help identify the builder.
    Tip: Our Focal Species Guide can be sorted by region to help you find potential breeding birds in your area.
  • Note the location of the nest. Is it on the ground? In a tree or shrub? On a building? Different species favor specific substrates for building their nests, and often the substrate (combined with habitat information and geographic location) will narrow down the possibilities considerably.
    Tip: Sort through the usual suspects using the substrate filters on our Focal Species page.
  • What is the composition and shape of the nest? Does it contain mud, feathers, sticks, pine needles, grasses, mosses, or another dominant component? Is it a cup, an enclosed dome with a side entrance, a platform, a hanging pouch, or messy bundle of sticks? Different species select particular materials when building their nests, and often this, along with the overall nest shape, can be a diagnostic key to the builder’s identity.
    Tip: A good field guide to nests will have a detailed description of the shape and most common nest construction materials for each species.
  • Warbling Vireo Nest
    Warbling Vireo Nest

    Vireos usually suspend their nests between a forked branch, with the nest hanging down below the level of the branch.

    Look at the size, shape, and color of the eggs, if present. The size of the eggs is related to the size of the parent, so small eggs will belong to small birds and large eggs to larger birds. Egg shape can also give important clues about the lifestyle of the layer. For example, eggs that are very pointed on one end are designed not to roll off of a cliff or out of a flat ground nest. (e.g., Killdeer, seabirds). The color and pattern, or lack thereof, on eggs will also help you narrow down the choices. Tip: Egg markings and color are highly variable, even within a clutch, and should be interpreted as supporting evidence, rarely definitive.
  • How many eggs are there? This can vary widely for many species, but some birds, such as Mourning Doves and hummingbirds, have very consistent clutch sizes.
    Tip: Our Clutch Size chart can help you pick some likely candidates.
    Tree nest of a squirrel
    Tree nest of a squirrel

    Don't be confused by tree nests, called "dreys", made by squirrels (when they're not nesting in cavities).


Bullock's Oriole nest
Bullock's Oriole nest

Orioles weave a hanging, pouch-like nest with an opening at the top, like this one.

Resources

Identifying the owner of a nest can be tricky, but fortunately there are many good books available on the subject. By noting the above characteristics in your field notebook and perhaps taking a few photos, you can identify your nest at home by comparing it to field guides. Here are some resources to help you solve the mystery:

  • Eastern Birds’ Nests or Western Birds’ Nests (Peterson Field Guides series), by Hal H. Harrison
  • Nests, Eggs, and Nestlings of North American Birds, by Paul Baicich and Colin Harrison
  • NestWatch Focal Species Guide

Remember not to take nests from the wild; it is always best to leave them where they are, even if you think they’re not being used.

Answer: From bottom to top, House Wren, Carolina Chickadee, and Eastern Bluebird built nests in this box.