Let me guess: Bird is hopping around, not quite able to fly?
Odds are it's a juvinile bird, recently fledged from the nest, and in the process of learning how to fly. The bird rescue I volunteer for gets close to 5 cases like this in our city every day, where people thought the bird was injured, but it was really just spending a few days practicing before it was good enough to get back into the trees again... and since flight is their only defense mechanism, this is an incredibly dangerous time to be a bird.
You might want to do the birds a favor, and keep the cat inside for the next few days, if not the next few months. Cat predation of songbirds is a pretty serious conservation concern; cats aren't native predators, and nestling and fledgeling birds are easy prey for them, which means the next generation of songbirds gets decimated by outdoor cats this time of year.
Songbirds are already under federal protection, but cats are driving many bird species toward extinction. A local study found that outdoor cats kill a bird a week on average, or 10 birds per outdoor cat, over the course of a breeding season. Doesn't seem like much, but when you add up the number of outdoor domestic cats, we see about 3.7 Billion dead songbirds every year. It's not the cats fault; they're just doing what they were born to do... but as stewards of our local environments, keeping them indoors during Spring is a simple thing we can do to help.
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