Q I opened a bluebird nest box to find dead chicks, overrun with large brown beetles. Did the insects kill the nestlings? The birds were almost old enough to leave the nest.
A No, the beetles didn't kill the birds. They were there to help clean up the mess.
First, the birds likely starved or were killed by blowfly larvae. Wet, cold weather could have prevented the adults from finding sufficient insects to keep their young alive during that period. Baby birds grow quickly; their energy demands are high.
Another possibility is that one of the adult birds was injured or killed, leaving the surviving parent with an impossible feeding job.
Or, an insect called a blowfly could have laid its eggs in the nest. Larvae hatch from the eggs and feed on the blood of the baby birds. The nestlings can survive a modest loss of blood, but will weaken and die if too many blowflies attack.
Beetle ID
Q What kind of beetles did I see? They were about half an inch long, dark brown with a cream-colored shell just behind the head, and a small crest-like mark.
A What you describe is the American carrion beetle. It does not eat dead flesh, but its larvae do. The beetles lay eggs on the dead animal. The larvae hatch in short order, and start feeding on the carcass. Flies also lay eggs on dead animals; their larvae are competitors for food once they hatch. The adult beetles eat the fly larvae to reduce the competition for food that their "babies" might face. (The scientific name of this beetle is cool: Necrophila Americana.)
