I live on the western part of Pa. And around here the robins never leave, we just don't always recognize them, because of their winter colors. I was told that they develop their red breasts,once the ground is soft(warm) enough for the earthworms to come out. Like flamingoes get their pink coloring from shrimp. Robins get their red from the earthworms, that they eat. So when the ground is warm, spring is near, and the Robins most definitive coloring returns .
I live on the western part of Pa. And around here the robins never leave, we just don't always recognize them, because of their winter colors. I was told that they develop their red breasts,once the ground is soft(warm) enough for the earthworms to come out. Like flamingoes get their pink coloring from shrimp. Robins get their red from the earthworms, that they eat. So when the ground is warm, spring is near, and the Robins most definitive coloring returns .