The Nazca Booby (Sula granti) was formerly regarded as a subspecies of the Masked Booby but is now recognized as a separate species. Nazca Boobies are known for practicing obligate siblicide. Mothers lay two eggs, several days apart. If both eggs hatch, the elder chick pushes its sibling out of the nest area, leaving it to die of thirst or cold. The parent booby cannot intervene and the younger chick inevitably dies. Two eggs are laid so that if one gets destroyed or eaten, or the first chick dies soon after hatching, the second egg will produce an offspring.
Nazca Boobies have a smaller range than Blue-footed Boobies but the Galapagos is the best place to look for them, especially Punta Pitt where you can see all 3 of the Galapagos boobies.
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VIDEO
This video has a sad element to it in regards to the siblicide. I usually try to avoid such videos but just about every video online has it and this one is produced by Nat Geo and is the best quality.