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 length – f:262, d: 264, m: 248; tarsus – f: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.