How to Identify Nests and Their Contents

Nests: Bluebird nests are nearly always exclusively made of grass. Tree swallow nests are started with grass and lined with feathers at the end. Therefore, it may be difficult to tell a bluebird nest from a tree swallow nest when the nest is just being started.

House sparrows use various items for their nests: grass, feathers, stems and sometimes man made materials such as tissue paper. Another clue to the house sparrow nest is that it will have a canopy over it. That is, it will fill the entire nest box and the nest itself will be a cavity in the middle.

House wrens use twigs for their nests. The male bird will start several nests and the female chooses the best one to lay eggs in. So do not be surprised when you find an unoccupied wren nest.

Eggs: Mountain bluebird eggs are usually pale blue, but can vary from a darker blue to nearly white. Clutch size can vary from 4 to 8 eggs, with the usual number being 5 or 6.

Tree swallow eggs are pure white and smaller than the bluebird eggs. From 3 to 8 eggs may be expected but anywhere from 4 to 7 is the most common.

House sparrow eggs are whitish but spotted and blotched with shapes of gray and brown. The most usual number of eggs is 4 to 6.

House wren eggs are pinkish white, but profusely dotted with pale reddish brown spots. Wrens lay from 4 to 9 eggs, with the most common numbers being 5 to 7. Wren eggs are, of course, the smallest of all.

Incubation periods: The time from when the last egg is laid until the young are hatched is approximately as follows:

All these species lay one egg each day and begin incubation after the last egg is laid.

Young: You will most likely have identified what species of young you have from identifying the nest, eggs, or nearby parent birds. The young go through three stages of development. The naked stage lasts about 5 days. The next stage is the pinfeather stage in the middle third of the growing period. In the last stage, the birds are fully feathered and growing further until the fledging date. (Young are best banded during the pinfeather stage. Before this, the birds are too small; and after they are fully feathered, there is a danger of premature fledging if they are disturbed too much.)

Date from hatching to fledging is approximately as follows: