Robin mystery solved

The Department of Criminal Ornithology has been investigating one of our most wanted culprits.. .the North American Robin. This bad guy is notorious for avariancide. While undercover...eh under bush, our lead field agent stumbled upon the drastic decline in local earthworm populations coincident with the ponderous growth in weight of  robins in springtime! We are presently serving over 60 million penal warrants!