Puffinus is a genus of seabirds in the order Procellariiformes. It comprises about 20 small to medium-sized shearwaters. Two other shearwater genera are named: Calonectris, which comprises three or four large shearwaters, and Ardenna with another seven species (formerly often included within Puffinus). The taxonomy of this group is the cause of much debate, and the number of recognised species varies with the source. Many are long-distance migrants, perhaps most spectacularly the sooty and short-tailed shearwaters, which perform migrations of 14,000 km or more each year.