That purpose is either good or bad.

Owls, crows, and turkey-buzzards, also the coyote, are regarded as forms assumed by evil spirits, or by men under the influence of evil charms.

The more Topanashka reflected upon the conduct of the birds, the more superstitious he became concerning them.

They certainly meant harm.

Either they sought to allure him into danger, or they indicated the presence of imminent peril.
Whatever that danger might be and wherever it might lurk, the man thought of nothing but to do his duty under all circumstances.