@misc{indiciae70c0f39b1aa9,
  title = {Adult Slaty-backed Gulls: Variability in mantle color and comments on identification},
  author = {M.E. Gustafson and B.G. Peterjohn},
  year = {1994},
  url = {https://pubs.usgs.gov/publication/5223883},
  note = {Source identifier: 5223883}
}