@misc{indiciae9bdb30daaf1f,
  title = {Population trends of black ducks and mallards from the North American Breeding Bird Survey: Are increases in mallards associated with declines in black ducks?},
  author = {J.R. Sauer and Sam Droege},
  year = {1997},
  url = {https://pubs.usgs.gov/publication/5211120},
  note = {Source identifier: 5211120}
}