Deserta’s Petrels

Deserta’s Petrel (Pterodroma desertae) is a newly described species recently split from Fea’s Petrel (Pterodroma feae) and previously included as a subspecies of Soft-plumaged Petrel (Pterodroma mollis). This species breeds on Bugio Island in the Desertas off Madeira.

Identification and Morphological Differentiation

As all three of the species in the Pterodroma feae / madeira / desertae complex were once believed to be subspecies of a single species: Pterodroma mollis. Well-understood is the extreme difficulty in telling them apart. A summary of data from a morphological study sheds light on the issue:

  • In overall size feae is closer to deserta and both are bigger than madeira (wing lengthf:262, d: 264, m: 248; tarsusf:34.7, d: 35.2, m: 32.7).
  • Bill length once again similar in feae and deserta and both larger than madeira (f:29.0, d: 28.6, m: 26.3).
  • Bill depth by far biggest in deserta, lowest in madeira, and intermediate in feae (f:11.9, d: 12.9, m: 10.5).

In terms of ratios:

  • (Bill length/wing length) (f:11.1%, d: 10.8%, m: 10.6%) is rather similar in the three taxa.
  • (Bill length/bill depth) (f: 2.44, d: 2.22, m: 2.53) is lowest in deserta, and highest in madeira. In feae it is intermediate, but more than twice closer to madeira than to deserta.
Photo of author

Team Beauty of Birds's team of experts includes veterinarians, biologists, environmentalists and active bird watchers. All put together, we have over half a century of experience in the birding space.

You can meet our team here.