Identifying baby bird eggs can be tricky for beginner birders. With over 10,000 species of birds worldwide, there is a huge diversity of egg sizes, shapes, colors and markings. However, there are some general tips and techniques you can use to help identify the most common backyard bird eggs.
Look at the egg’s size
One of the first things to look at is the size of the egg. While there can be variation even within a species, in general larger birds lay larger eggs and smaller birds lay smaller eggs. For example, an emu egg can be up to 6 inches long while a hummingbird egg is only about the size of a pea. Backyard bird eggs tend to range in size from a few centimeters long to a few inches long. Here are some common backyard bird egg sizes:
Bird Species | Egg Size |
---|---|
American Robin | 1.5 inches long |
Northern Cardinal | 1 inch long |
Chickadee | 0.6 inches long |
House Finch | 0.8 inches long |
So if you find a tiny egg that’s less than an inch long, it likely belongs to a songbird like a chickadee or warbler. A medium 1-2 inch egg may belong to a robin or cardinal. And a very large 3+ inch egg probably belongs to a bird of prey like a hawk or owl.
Identify the egg’s shape
The shape of an egg can also give clues to what species it belongs to. Most backyard bird eggs have one of four general shapes:
- Pyriform: Long and tapered on one end, like a pear. Examples are robins and thrushes.
- Elliptical: Symmetrically oval shaped. Examples are finches and cardinals.
- Rounded: Nearly circular. Examples are owls, woodpeckers and kingfishers.
- Conical: Large end tapers to a point. Examples are hummingbirds and some shorebirds.
So if you find a tapered, pyriform egg in your yard, it likely belongs to a robin or thrush. A very rounded, circular egg may come from an owl or other raptor. Noting the overall shape can help narrow down possibilities.
Check the egg color
Egg color is another important identifier. Bird eggs come in a rainbow of colors from white and cream to pink, blue, green and brown. Here are some common backyard bird egg colors:
- White/Cream: Robins, doves, sparrows
- Pale Blue: Chickadees, thrushes, finches, woodpeckers
- Pinkish: Warblers, blackbirds, night herons
- Speckled: Thrushes, mockingbirds, owls, egrets
- Brown/Tan: Hawks, quail, swifts, grouse
A bright blue egg likely belongs to a songbird like a finch or chickadee. A brown or heavily speckled egg may be from an owl or hawk. However, keep in mind that the female’s diet can affect egg color so there may be variations even within a species.
Look for markings
Markings such as spots, speckles and scrawls help camouflage eggs and also aid identification. Here are some common backyard bird egg markings:
- Heavily spotted: Towhees, thrushes, woodpeckers, grosbeaks
- Light speckling: Flycatchers, cuckoos, bluebirds, mockingbirds
- Dots and scrawls: Egrets, terns, kingfishers, mourning doves
- Plain unmarked: Pigeons, hummingbirds, swallows
An egg splattered with large dark spots likely belongs to a towhee or thrush. Fine uniform speckling may indicate a bluebird or flycatcher laid the egg. And a plain unmarked egg probably comes from a dove, pigeon or hummingbird.
Know when birds breed
The time of year when an egg is found can provide helpful clues. Many birds only breed during certain seasons or months. Here are breeding times for some common backyard birds:
Bird Species | Breeding Season |
---|---|
Chickadees | April-July |
Robins | April-July |
Mourning Doves | March-September |
Hummingbirds | March-June |
Woodpeckers | April-July |
Finding an egg during a bird’s typical breeding season makes it very likely to belong to that species. Discovering a blue-speckled egg in March is a strong indicator it’s a robin’s egg. While finding the same egg in December rules out that possibility.
Use a field guide
A field guide that illustrates different egg sizes, shapes, colors and markings can be invaluable for identifying unknown eggs. Cross-reference your observations with the guide to find likely matches. Remember to consider location – guidebooks focused on your state or region will provide the most accurate information on which birds breed nearby.
Observe the parents
If possible, try to observe the adult birds at the nest. Seeing the parents caring for the eggs or hatchlings will conclusively identify what species laid them. Be careful not to disturb or stress nesting birds when observing them.
Parent birds may also leave tell-tale evidence behind:
- Owl pellets and feathers indicate an owl nest
- Half-eaten seed shells point to finches or doves
- Rotting fruit hints at a thrush nest
- Coarse sticks and twigs signal a big nest like a hawk or crow
Use contextual clues like these to make an ID if you can’t directly see the parents.
Consider the nest location
Where the nest and eggs are found provides valuable clues to the parents’ identity. Different birds nest in different habitats and locations:
- Tree cavities: Chickadees, woodpeckers, bluebirds
- Ground/Shrubs: Sparrows, towhees, quail
- Platforms: Robins, doves, ospreys
- Cliffs: Hawks, falcons, ravens
- Wetlands: Herons, bitterns, marsh wren
For example, a nest in a marsh or wetland signals ducks or herons, while a tree cavity points to woodpeckers or other cavity nesters. Use the nest location and habitat to inform your ID.
Consider egg number
The number of eggs in a nest can also hint at the parents. Songbirds and smaller birds often lay 4-6 eggs. Larger birds like hawks and herons typically lay only 1-3 eggs. And nest parasites like cowbirds always lay just one egg.
Finding a nest with just 1 or 2 eggs may mean it belongs to a bird of prey or other large bird. A nest with 4 or more eggs probably belongs to a smaller songbird.
Use an incubator
As a last resort, you can carefully incubate the eggs to hatching. Borrow or purchase an incubator that allows viewing windows into the eggs. Maintain proper temperature and humidity levels. Candle the eggs periodically to monitor development. Ideally, the eggs will hatch after their species’ normal incubation period, conclusively revealing their identity.
However, this process requires experience and diligent monitoring. Work under guidance from an avian expert or wildlife rehabilitator when attempting egg incubation and hatching.
Get help from an expert
If you are still uncertain what species laid an egg, seek help from knowledgeable birders or avian experts. There are online forums, Facebook groups, subreddits and more dedicated to birding and egg identification. Or contact local nature centers, universities or bird rehabilitation facilities in your area – many employ experts who may be able to conclusively identify mystery eggs.
Proper identification is important, especially if you plan to monitor the nest or eggs. Misidentification can lead to inadvertent disturbances or interventions that may harm the developing chicks. When in doubt, reach out to reliable experts.
Conclusion
Identifying bird eggs takes practice, but careful sleuthing can crack the case. Start by looking at size, shape, color and markings. Reference field guides and note the location and habitat. Consider the number of eggs and when birds breed in your area. Observe parent birds and nests when possible, but do not disturb active nests. If you remain stumped, don’t hesitate to consult birding experts who can help definitively ID challenging eggs.
With some detective work, you can learn how to read nature’s Easter eggs. And correctly identifying backyard bird eggs is rewarding for appreciating and supporting local wildlife.