Kira Rambles

As part of my job at a living history site, I give maritime history boat tours on Lake Champlain’s southern basin. Before those tours, in addition to completing engine checks and stocking the boat bar, I fight in my boss’ turf war against the local seagulls. 

My battle? The poop they leave on the tour boat dock. I scrub it off the wood planking and metal ramps with a bucket of lake water and a cheap blue plastic mop. Our mop is much bluer than the silty, sage-colored lake, but, even though you could describe Champlain as gray-green, it’s got nothing on the nuclear lime yolks in some of the poop piles. 

Washing those piles off the dock gives me time to study their contents and wonder, what could make poop that green? 

When you google “what makes seagull poop green,” the algorithm populates when to worry about your own green, human poop. But it also offers some interesting information about the value of seagull scat. 

Poop, or even scat, isn’t the correct terminology, though. Like bat excrement, sea birds produce guano. 

The Oxford English Dictionary says guano first popped up to represent this specific poop in the English language around 1604, when one Edward Grimeston translated it from Spanish. The Royal Spanish Academy traces the origin farther back to the Quechua wanú, meaning fertilizer, which makes sense considering guano and mined deposits of its nitrates have fertilized the Americas and Europe for centuries; massive sail cargo ships brought guano from the west coast of South America around Cape Horn and across the Atlantic as part of the highly profitable nitrate trade that contributed to Chile annexing guano-deposit-rich Peruvian and Bolivian territory after the War of the Pacific. 

The ethics of the nitrate trade are questionable; overfertilization can lead to environmental degradation, and nitrates are an ingredient of gunpowder. However, since the nutrient content in guano nourishes marine ecosystems, and many seabirds are endangered, scientists suggest monetizing their poop may incentivize conservation. 

Maybe I’ll become a double agent and advocate for the seagulls. Maybe we could use their guano as fertilizer in the fort garden… 

Anyways, the Audubon Society says uric acid makes bird poop white. They don’t pee, so their solid waste includes byproducts from the kidney filtration process. Incidentally, that uric acid is what gives guano such a high nitrogen content. 

I still don’t know what makes it green, though.