To cite auk in publications use:

Matthew Strimas-Mackey, Eliot Miller, and Wesley Hochachka (2018). auk: eBird Data Extraction and Processing with AWK. R package version 0.3.0. https://cornelllabofornithology.github.io/auk/

Corresponding BibTeX entry:

  @Manual{,
    title = {auk: eBird Data Extraction and Processing with AWK},
    author = {Matthew Strimas-Mackey and Eliot Miller and Wesley
      Hochachka},
    year = {2018},
    note = {R package version 0.3.0},
    url = {https://cornelllabofornithology.github.io/auk/},
  }