Sounds like grubs to me. Have the same problem here with the crows coming in and tearing up the turf to get to the grubs. Makes quite an unsightly mess. If you're licensed, Grub-X works well for treatment. Just be sure to do the entire lawn including landscape beds and not just the "problem" areas. Grubs do not discriminate. It may take a couple seasons to get them totally under control.
or even if you ARE licensed, your local county Extension Agent (sometimes known as the Agricultural Extension Agent) may be a good source of free information. Around here he will even make on-site diagnoses.