House Wren eggs

• Color: white or pinkish, heavily dotted with reddish brown. Markings vary between females and are often heaviest around the wide end; the same female tends to lay a similar pattern every time.
• Size: 15–18 mm long by 12–14 mm wide. For scale, a US quarter is 24.3 mm across, so this egg is about 68% of the width of a US quarter.
• Where you find it: almost any cavity — boxes, gourds, even boots and flowerpots; males build several stick-filled dummy nests. House wrens also use nest boxes with a 1 to 1 1/8 in round entrance, so eggs in a box are a strong clue.
• Clutch: 3–10 eggs. A nest with far more eggs than this may hold eggs from two females, or a cowbird egg laid by a brood parasite.

These species lay eggs in the same color group, sorted by how close they are in length. Size and nest site usually settle it.

Laying starts earliest in Arizona (Apr) and latest in Alberta (Jun). Months are estimates from regional breeding data shifted for latitude.

Eggs hatch after 9–16 days and the young leave 15–17 days later. See the full baby House Wren guide for nestling stages and what to do if you find one on the ground.

• Leave them. Parents often step away for long stretches, especially before the full clutch is laid, because most songbirds do not start incubating until the last or second-to-last egg.
• A single egg on the ground is usually lost for good. Eggs cannot be hatched at home, and possession of native bird eggs is illegal without a permit.
• If a nest is somewhere inconvenient, wait it out. Most small songbirds are done in three to five weeks.
• Watch from a distance and keep pets indoors. Repeated visits can lead predators to the nest.