“the birds of the air.” The Hebrew is literally, “the birds of the heavens,” but the Hebrew word “heavens” is always plural, there is no singular word “heaven” in Hebrew.
“and to the animals of the field.” In a culture where family ties were strong and family tombs common, to not have anyone bury your dead body was considered a terrible curse. In fact, many people believed (falsely, but it was a very widely held belief) that a proper burial was important for a comfortable existence in the afterlife. Thus the threat of not being buried but having one’s dead body eaten by animals, birds, and vermin was a horrifying threat of unspeakable loneliness and rejection, both on this earth and in the afterlife (see commentary on Jer. 14:16).