A Crowded Summer Colony on the Lower Cape

Jun 13, 2018

 

Common Tern
Credit Mark Faherty

Just offshore of Chatham there lies a seasonal village you may not be aware of. The residents arrive promptly and noisily each May, then leave for their winter homes again around October. During their stay, they create chaos, noise, and traffic - well, air traffic at least – in pursuit of beach space and local seafood. And summer wouldn’t be the same without them. Surprise! I’m actually talking about birds. What are the odds?

 

Monomoy National Wildlife refuge in Chatham hosts the largest tern colony on the east coast, home to many thousands of nesting Common Terns and Laughing Gulls each summer. The young seasonal biologists at Monomoy are tasked with monitoring the success of the colony each year. Imagine asking a handful of childless millennials to keep track of 50,000 youngsters, because that’s how many chicks there are in this colony. How do they do it? The answer is they closely monitor every nest within several small, representative plots, and extrapolate to the rest of the colony in terms of how many chicks fledge.

 

To estimate the size of the colony, the refuge biologists organize a complete census, where no nest goes uncounted. I was lucky to be able to help with one day of the two-day annual census last week, and to get a window into the life of a seasonal biologist in the colony. The researchers actually live in the colony, in tents set up for the summer, which is apropos because intense is a good description of life among the terns. They walk out the door and there are tern nests. They go anywhere and there are tern nests. And where there are tern nests, there are angry terns with sharp bills and a vendetta.

 

There’s no construction going on, but the colony is definitely a hard hat area. As for entering the colony without a hard hat, well, you need that like a hole in the head. And there are 25,000 birds who would be happy to create that hole for you. I had one tern that learned to aim for a little gap between the back of the helmet and the adjustable band, which he hit with vicious precision several times. But the joke was on him, since I don’t use my head for anything.

 

The terns have good cause to be defensive, as there are island residents less benevolent than the biologists. Night-herons and coyotes take their share of eggs and chicks, and this year, a Snowy Owl has decided to stay for the summer. Typically these high-Arctic owls are gone from the Cape by April, so this guy is a real rebel. Apparently, the uncertainty supply of lemmings back home combined with the limitless supply of easy prey here was too good to pass up. We encountered several low hillocks where the owl had been feeding the night before, leaving behind pellets and piles of tern wings. It’s way too late for this owl to make it back to the Arctic to breed, so he may just stay for the summer. If the terns were smart, they’d follow the lead of many local landlords looking to get rid of unwanted winter tenants – they’d jack the rent way up for the summer.

It takes a while to crunch the numbers, so the final census tally won’t be in for a while. Based on past results we’re expecting somewhere north of 10 or 11,000 Common Tern nests and over 1000 Laughing Gull nests. In a typical year, each pair fledges 1.5 chicks, which is very high for a species that can live 25 years, pointing to the incredible productivity of the fish-rich waters around Chatham. To get in on the action, contact the refuge about volunteering next year. Because who doesn’t love an unpaid 14 hour day spent dodging sharp beaks in a non-stop poop storm?

 

You can see Mark's photo album from the 2016 census here.