Blue-footed booby chicks were put in masked booby nests and vice versa, to determine whether parents, or offspring, or both, controlled the siblicide. In masked booby chicks raised by blue-footed booby parents, siblicide happened in 80 percent of the nests, compared to the normal 100 percent when masked booby chicks are cared for by masked booby parents. About half of the blue-footed booby chicks killed their siblings when raised by masked booby adults. "The masked booby parents seem to be collaborating with the first chick to get rid of the second chick," Anderson said.
Moreover, work by Andrea Schwandt, a Wake Forest graduate student working in Andersons Galapagos laboratory, suggests that masked booby parents even stand over their chicks to give the attacking bird more room to maneuver. The masked boobies nest, flatter than the blue-footed species, may also make the ejectors job easier. In contrast, blue-footed booby parents squash their chicks down into their bowl-shaped nests.
Despite the evidence of collaboration between masked booby parents and their firstborn chick in siblicide, Anderson has not yet completed analyzing data to answer the ultimate question: the long-term effects on booby adults forced to raise two chicks.
But preliminary data clearly show a cost. "They show up at the colony in about the same frequency the second year, but are much less likely to breed," said Anderson, who visits the Galapagos each fall to set up his research teams camp, returns in July to close another season of data-gathering, and supervises the team through computer e-mail and satellite telephone.
"The parents are tuckered out from the year before," Anderson said. "If the rest of our data show the same trend, then you would say that parents seem to maximize their long-term reproductive success by collaborating in the siblicide, because the effo
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Contact: Wayne Thompson
thompsow@wfu.edu
910-759-5237
Wake Forest University
6-Dec-1996