Aves Non Grata - The Blue-footed Booby

I pushed my sister off the roof our house once. I meant no harm. We were simply filming what we expected would be the big winner on America’s Funniest Videos. When her cue came and she didn’t jump, I pushed her. That’s what big brothers do. She was fine. Anyway I have two more sisters where that one came from.

Booby with chick © Pete Corradino

Blue-footed Boobies (Sula nebouxii) are occasional visitors to the United States but they nest primarily along the Pacific from Mexico south to Peru. They are opportunistic nesters, laying between 1-3 eggs on the ground inside a curious white ring. The eggs are laid and incubated asynchronously and hatch in the order in which they were laid. If times are good, everyone gets fed and fledged. When food is scare, competition sets in among the hatchlings who participate in siblicide. They kill their own brothers and sisters. In theory, the first hatchling has the upper hand, or wing as it were, which they use to push the younger siblings out of the nest. In some cases they can push them off a cliff edge but here’s where the mysterious white ring comes into play. What looks like a monochromatic circle of spin art is a fecal ring. The female will rotate around the center of the nest and squirt feces and uric acid in a scattershot pattern.

White fecal ring around nest © Pete Corradino

During a trip to Ecuador I had an opportunity to see the nesting behaviors and artistic displays firsthand. The Blue-footed Boobies will let you approach and seemingly don’t even recognize your presence until you step across the magic white fecal line (which I did not do out of respect for the wildlife). Now facing a threat, her pointed beak becomes all business. Anything within the circle conversely must be protected.

© Pete Corradino

A hatchling does not understand this. They understand hunger and survival. When they push their siblings, hatched or unhatched, across the magic line, the female booby suddenly earns her name. Beyond the line, her young become aves non grata.

© Pete Corradino

It had never occurred to me that with one less mouth to feed I’d have a greater opportunity for more food. In fact our incident on the roof had the opposite effect. No dessert that night and no more access to the roof.