Seeing a dead bird in superstition can mean two things.
Some people think that seeing a dead bird symbolizes that a loved one has died or is gonna die soon.
Other people think that seeing a dead bird means that good things are gonna happen to you or someone or something good has already happened to you or someone.
So seeing a dead bird can mean either bad things or good things but it's just superstition that some people believe in.
In reality the bird has just died of either sickness or natural causes.