Birders like us love to find a nest of wild bird eggs, but do you always know what you’re looking at? The easiest way to tell is to observe the nester coming and going. Of course, if you see the nester feeding its nestlings, it’s a sure thing.
However, many different species may land on or check out another bird’s nest. Other birds may even take over a nest started by another species. If two species are laying claim to a nest, both of their eggs could be in it at the same time. Also, unless the nest is removed after each season, material from previous nestings can confuse any identification.
Some birds, such as House Sparrows and House Wrens, have a tendency to enter a bird box or nest to attack the nester. Usually these birds make themselves very visible by sitting on the box. House Sparrows are non-native, invasive pests and are not protected by law. They will attack and kill adult bluebirds and destroy eggs and young. Therefore, you may legally remove or destroy a House Sparrow’s nest. If you have a blue bird box, keep an eye out for House Sparrow invasions.
With all of the nesting confusion, the eggs are the easiest way to tell what sort of bird’s nest you’ve found. Wild bird’s eggs have different colors, markings, sizes, shapes, and glosses to them. For example, House Sparrows’ eggs are a cream tint with irregular fine brown speckles. The shell is smooth with a slight gloss. However, the size and thickness of spots vary. Tree swallows’ eggs are pure white with a pointy end.
Observe the nests and take pictures, but do not touch them unless they have been discarded. In many areas, it is illegal to disturb the nests of wild birds.
Nest and egg description charts come in handy for an amateur. Keep an eye on your nests—the eggs will hatch within two to three weeks!