Why do black birds thow robins eggs out of their nest then lay their eggs in the nest for the robin to incubat

Question

I have seen black birds do this in our back yard. Then the poor robin knows no different and raises the black bird as it"s own.

Answer 1

A mere microcosm of society.

Think about it.

Answer 2

It's got no particular reason not to, should the behaviour be advantageous to the blackbird.

Answer 3

That's the brown-headed cowbird.  That's the way they bring new cowbirds in to the world.  It's called egg dumping and nest parasitism.  Since they have been doing in for millions of years there's absolutely nothing wrong with it.  After all they and the other birds have adapted to this behavior.

Yes, the American robin is a common target for cowbirds.  Any bird about that size and makes a nest in relative open could be parasitized by the cowbird.  You can not interfere with this process either, both species are consider songbirds and are protected by law.

http://www.birds.cornell.edu/AllAboutBir...

Answer 4

Some birds act like parasites to other birds. The bird is using the robin to raise its young. The robin will never know and eventually end up raising the blackbirds baby to adulthood.

There are many birds that do it that rarely ever nest themselves.

Such as the brown headed cowbird.

Answer 5

As for why they parasitize nests, it is advantageous to do so.  The parasite does not need to expend any time or energy raising its own young.  It can concentrate simply on laying as many eggs as it can during a breeding season and leave the actual raising of the chicks to the unknowing host parents.  The parasite birds maximize the number of their offspring.