Why can’t I delete some of my nest sites?
You may have already entered nest attempts (data) for that nest site. In order to delete the nest site you must first delete all nest attempts associated with that site.
Read here for instructions on how to delete erroneous nest data.
Alternatively, if your nest site does not have any data on it, and you still don’t see the delete button on the Site Summary page, then double check whether that nest site has been added to a group. Click the “Manage Your Groups” button on the My Nests homepage to see all of your groups. Make sure the nest site you wish to delete does not have a checkmark next to it for any of the groups you’ve created. A nest site cannot be deleted if it is part of a group.