Question: do blue jays take over other birds nests

Answer: Yes, Blue jays are not very picky about nesting locations. If no better place is available -- e.g. in a heavily deforested area -- they will even use places like the large mailboxes typical of the rural United States. They also appropriate nests of other mid-sized songbirds as long as these are placed in suitable spots; American robin nests are commonly used by blue jays, for example.