Bird guides have pictures of “breeding plumage”–but how long does breeding plumage last? Does a bird have it for only 3 weeks? for half the year? How do I know when to look for breeding plumage, and when to look for nonbreeding plumage?
It’s species-specific, and I believe to a lesser extent can also be population/location/individual-specific within a species. But in general the cycles are a period of months.
A good field guide (I’m a Sibley fan) will give you an idea by captioning the illustrations with a range of months. Is there a particular species you’re wondering about? I can give more details if so.
Some examples:
Reposted from https://lies.tumblr.com/post/619816433115873280.
