Hunlock Creek PA
2011

In a robin couple, a male brings his female partner nesting material as she constructs the robins’ nest. The female builds the cup-like nest with mud as its foundation and lines it with grasses, twigs and other plant material before laying bright blue robin eggs.

Mud is an essential part of robin nest architecture. The foundation is constructed of mud that holds the nest together like cement. The mud is typically gathered from a ready source, such as the edge of a puddle or earthworm castings. In drier years, robins have to be more resourceful and manufacture their own mud. They’ve been observed carrying dirt in their bills to a bird bath to soak, and splashing in a bird bath before flying to a spot of dust and shaking the water off. There’s a good chance that the birds you observed were soaking nest material to make mud.

Robins nest all across Alaska and Canada and in most parts of the lower 48 states, except for the hottest southern regions. They build nests on branches or ledges. Robins will also happily nest in planters, on windowsills, and in other nooks and crannies around a building. The birds may use flower petals or scraps of paper, string, or cloth on the outside of the nest. It may look like they are simply decorating, but these things serve as camouflage by breaking up the dark outline of the nest, helping it to blend in better with the patchy light and shadows.

Female robins lay only one bright blue egg per day and typically lay three or four eggs total, seldom a clutch of five. Robins raise up to three or more broods a year, especially in the southern part of the United States.