St Clair, J. J. H., Klump, B. C., Sugasawa, S., Higgott, C. G., Colegrave, N., & Rutz, C. (2018). Hook innovation boosts foraging efficiency in tool-using crows. Nature Ecology & Evolution, 2(3), 441-444. doi:10.1038/s41559-017-0429-7.