What is Carson alarmed about?

He autumn months to which she referred brought other somberreports from the deep South, where in Mississippi, Louisiana, and Alabama the Field Notes published quarterly by the National Audubon Society and the United States Fish and Wildlife Service noted the striking phenomenon of "blank spots weirdly empty of virtually all bird life." The Field Notes are a compilation of the reports of seasoned observers who have spent many years afield in their particular areas and have unparalleled knowledge of the normal bird life of the region.

Source: e2020 eResource