@misc{indiciaecf2ace3917ee,
  title = {Fifteenth breeding-bird census. 13. Mature northern hardwood forest},
  author = {C.S. Robbins and R. E. Stewart},
  year = {1951},
  url = {https://pubs.usgs.gov/publication/5220186},
  note = {Source identifier: 5220186}
}