UPDATED April 28: The Case of the Vanishing Blue-Footed Boobies

Blue Footed Boobies

file photo / Galápagos Digital

Blue Footed Boobies

They are the avian equivalent of the giant tortoises–emblematic of the Galápagos–the blue-footed boobies that populate the islands and entertain human visitors as they dive headlong into the ocean for food.  But now, according to a new study, their population has been seriously dwindling by more than two-thirds in the last half century.

The number of birds as of 2012 was down to 6,423, compared to an estimated 20,000 in the 1960s.  Researchers say one reason for the decline may be a scarcity of sardines in the waters between Galápagos and the South American coast.  Sardines are the boobies’ main food source.

Looking at the ocean waters off the coast of Peru, hundreds of miles southeast of Galápagos, the study said, “The sardine population there has declined almost to zero.”  Scientists hypothesize that the reduced sardine supply causes the birds to stop reproducing.

“Until 1997, there were literally thousands of boobies at these breeding sites, and hundreds of nests full of hatching chicks,” principal investigator Dave Anderson, a biology professor at Wake Forest University said in a press release.

“Then, suddenly, the boobies just weren’t there,” Anderson said, adding that, in a few cases, the birds had attempted to breed, but most did not produce offspring.

And there may be fewer still in the years to come.  Anderson and the other researchers noted that the population of boobies is aging and that they’re not reproducing at a normal rate.

“Few pairs bred in 2011-2013,” the study said, “And almost no birds were found in juvenile plumage.”

As Galápagos Digital reported April 10, the impending threat of a huge El Niño in the Pacific this coming winter could further disrupt the food supply in Galápagos.  While cautioning that some of the El Niño warnings may be overblown, Anderson said in a note to Galápagos Digital, “If El Nino DOES happen and it DOES make food conditions worse for blue-footed boobies, then breeding might become even less likely.”

2014 has not shaped up as a good year for the blue-footed booby in Galápagos.

This article has been corrected from the original version.  The scientists who did this study have no hard data on why the sardine population crashed off the coast of Peru.

We’ve linked a YouTube video of Dave Anderson discussing the research.