Birds and Molting Feathers
It's very common to find bird feathers lying on the ground. Just as humans shed hair and regrow it, birds molt their feathers and grow fresh, new ones.
First, an important note. Because of the serious damage that feather-gatherers did in the late 1800s, destroying entire populations of birds by gathering the feathers of the still-living birds, it is now illegal to have feathers of pretty much any species. The logic is that if you are caught with feathers, you could always claim "Oh, I found them on the ground." So by making possession of them illegal, the criminals would have no excuse. So bring a camera to take pictures of the feathers you find, but don't pick them up.
Just about every bird molts once a year. Molting isn't an "all at once" process - a bird doesn't drop all its feathers and then start growing a set of new ones. Instead, the bird waits until all of its chicks are out of the nest. That way its serious flying duties are done for the year.
Next, the bird starts dropping off a portion of its old feathers. New ones begin to grow in. Using a gentle cycle, the bird continues to lose old feathers and grow new ones. The bird can always fly, just not very well during the middle period. After 2-3 months, the new feathers are completely in and the bird is ready for the fall and winter harsh weather.
This cycle is true for owls, for crows, for blue jays, and for most other birds. They need those fresh feathers to keep warm, to fly, and to attract mates.
One exception to this rule is the Canadian Goose. These creatures lose most if not all of their primary flight feathers when they are nesting. They stay on the ground, defending their nest from attackers during this time. This allows them to be fully flight capable at all other times except during the molt period - a time when they should NOT be abandoning their nest anyway.
Male mallards also become flightless for about a month in the late spring, and are often confused with female mallards at this time. Again, it coincides with when the males should be home defending their turf, and not off soaring in the sky.
Birding Basics
Birding Tips and Photos
Birding Help Hints Tips and Information