@misc{indiciae28415e56431a,
  title = {Demography of eastern population tundra swans, Cygnus columbianus columbianus},
  author = {J. Bart and R. Limpert and S. Earnst and W. Sladen and J.E. Hines and T. Rothe},
  year = {1991},
  url = {https://pubs.usgs.gov/publication/5210541},
  note = {Source identifier: 5210541}
}