[All photographs copyright, Scottie Schmidt 2015] Local marine mammal observer Scottie Schmidt snapped these incredible photographs of a Masked/Nazca Booby on board the Hornblower whale watching tour out of San Diego on 01 September 2015. The Hornblower, performing a four hour tourist nature tour, stays in US waters just outside of Point Loma where it looks for whales and dolphin. Scottie noted that he has been on hundreds of these trips aboard the Hornblower but this was the first time a booby had actually landed on the vessel!
I think characters of this 2nd-cycle booby lean towards identification as a Nazca Booby rather than a Masked Booby. The bill color, pale lavender at the base changing to pinkish throughout the length and then yellow-orange at the tip, is basically a duller version of adult Nazca Booby. Masked Booby should be yellowish-green changing to yellow at this age. Also the bill shape, more concave and finely shaped, seems to fit Nazca better compared to the swollen more massive bill shape characteristic of Masked. Other plumage characters might be supportive also, the white basal coloration of the central rectrices appears to extend quite far down those feathers, and the dark plumage looks more chocolate-brown than blackish-brown. Both characteristics better for Nazca compared to Masked.
Scottie Schmidt first sent these photographs over to Stan Walens who distributed them to local San Diego seabird enthusiasts for further discussion. The photographs were also examined by Alvaro Jaramillo.