Why do robins throw out their eggs/new hatchlings?

Question

robin made 3 eggs, then a day later had another 1. then 1 hatched. day n a half later the new baby and 2 of the eggs were gone. only 1 egg left. what the heck happoned?

Answer 1

Sounds like a predator got to the nest and ate them.  This is very common..only about 30% or all nests  are actually successful.

Answer 2

Robin didn't use protection

Answer 3

Either a predator like a crow raided the nest or the first hatchling shoved its competition out of the nest.  Heck, it might even have been attacked by a house sparrow.