First San Diego County specimen of the Nazca Booby
Today Lea Squires prepared San Diego County’s first specimen of the Nazca Booby, found freshly dead on a buoy off 24th St., National City, by boater Mark Woodruff on 5 May 2018. Mark had seen the Nazca Boobies in that area earlier this year and recognized the dead bird as that species too. But, remarkably, it was not one of the same individuals, which were full adults, but a subadult in which the bill was just becoming orangish. Most likely it was the same subadult seen alive by Matt Sadowski in the bay off Chula Vista on 1 May. The bird had an empty stomach and was somewhat emaciated; it had not swallowed a fishhook, as so many of the boobies we receive have. It was molting over much of the body plumage, the primaries, and three rectrices (the outermost two plus one intermediate rectrix were growing in). The head was still speckled with brown, as were the wing coverts and rump.
This incursion of the Nazca Booby thousands of miles from its normal range may represent bad news for the species. A study published last year (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0182545) links lowered reproductive success of the Nazca Booby in the Galapagos to a shift from a diet of sardines (8% fat) to less nutritious flying fish (<1% fat), a shift that took place in the wake of El Niño of 1997-98 and has not been reversed since. And the authors warn that the increasing ocean temperature is likely to preclude the anchovy population of the Galapagos from recovering. Perhaps 15 to 20 years of a diet of leaner fish is driving the Nazca Booby to search far beyond its normal range for better feeding.
In any case, this new specimen is the for California that shows the distinctive bill color of the species. It is now catalog number 55680 in the museum’s bird collection. The first specimen for California, preserved in the Western Foundation for Vertebrate Zoology, was an immature found long dead and dried on a beach in Ventura County on 27 July 2013. The identification of that specimen was confirmed by genetic analysis of the feathers (https://www.westernfieldornithologists.org/archive/V47/47(1)-p058-p066.pdf).
Source: SanDiegoRegionBirding Latest Reports