Fake Least Tern Colony

An adult least tern in breeding plumage.

Least terns are the smallest American tern, measuring only nine inches long. They’re awkward on land, with oversized wings and tiny legs, but graceful in the air as they soar and dive. They’re also federally endangered in the interior US and threatened in several states, including Rhode Island. 

A least tern nest.

Least terns nest on sandy beaches. They dig shallow depressions in the sand, called “scrapes,” and lay two eggs. The eggs are well camouflaged with a sandy-gray color and black splotches, but the breeding adults are downright gaudy, with jaunty black caps and white unibrows. They nest in raucous colonies, shouting their presence to the world. This approach is perhaps a little foolhardy, for least tern chicks and eggs are little more than tasty snacks for seagulls, crows, foxes, feral cats, and other predators. Least terns aren’t defenseless, however; they will dive bomb and defecate on any predator that dares approach.

Due to their threatened status, least terns are monitored by the Fish and Wildlife Service – who I’m working for this summer as an intern. As part of an ongoing effort to protect least terns, this year we installed an electric fence in one of the overwash areas at Quonnie Beach. A shock is only provided if two wires are touched simultaneously, so predators like foxes, skunks, and raccoons get a small shock if they try to cross, but piping plovers and other small shorebirds can run through the bottom of the fence without problem. The fence is solar powered.

Of course, an electric fence doesn’t do any good if the least terns nest outside of it. So in mid-May we set up a fake least tern colony.

A fake least tern.

For the fake colony, we set up two solar powered speakers that broadcast the recorded calls of a real least tern colony. This attracted the interest of one or two least terns that flew by and called out while we worked. Next we arranged plastic terns around the speakers, carefully spacing them a meter and a half apart with an even ratio of couples and singles. Prior studies suggested that the fake colony would work, but holding the fake terns in my hands, I wondered if the real terns would be taken in. And just how badly would they be fooled? Would a clueless male attempt to woo a plastic bride with a freshly caught fish?

A crow attacking a fake least tern.

The first bird to approach the colony wasn’t a least tern at all, but a crow.  A bold bird, it flew down and approached the dummy terns before we left the fenced area. This was a source of concern since crows are known to prey on least tern chicks and eggs – a trait the crow demonstrated by attacking the dummy terns. Perhaps baffled by the terns’ stubborn refusal to fly away upon its approach, the crow approached the dummy terns from behind and pecked at their tails. No luck; the dummy terns remained in place, keeping their hypothetical eggs well hidden. The crow stepped back and examined the dummy terns from a different angle before trying again. Still no luck. Giving up, the crow flew away.

An annoyed piping plover.

The second bird to be fooled was a piping plover, a small, sand-colored shorebird that also likes to nest on sandy beaches. This particular bird had established a territory nearby and came over to give those obnoxious terns a piece of its mind. It ran about and peeped at them; “Mine! Mine! Mine!” Eliciting no stronger reaction than the crow, the plover left.

Within an hour, the stars of the hour arrived. Gee, those dummy least terns sure picked a fine location for a colony! A nice flat, sandy stretch of beach, just the ticket. Two terns flew down and started scraping. Other terns landed nearby.

This annoyed the piping plover all over again. Returning, the piping plover resumed its peeping, but the real terns were even less impressed than the fake ones. Not even the plover’s aerial display made them budge. This was their colony and they were staying.

*****

 A real least tern examining some fake least terns.

Now that three weeks have passed, I wish I had good news to share about the colony. I wish I could say that all of the terns are nesting where we want them to, well within the electric fence and away from the nearby sand road. That isn’t the case. A glitch in the MP3 player made it freeze and a strong wind blew over and scattered most of the dummy terns. We’re responsible for monitoring twelve other beaches and can’t check each beach every day, so it took several days to fix the dummy terns and even longer to find the source of the error with the MP3 player. In the mean time, the real least terns decided to pick their own colony location – and settled on nesting just outside the electric fencing. A few pairs at the edge of the colony are inside the fencing, but the majority of the colony is unprotected. It took a full day to set up the electric fencing and it would take just as long to move, creating a huge disturbance for the birds. For that reason alone, moving the fencing isn’t an option.

Fortunately none of the terns decided to nest in the sand road, but it’s still disappointing to see so much hard work come to so little. Of course this is the first year the electric fence and fake colony were attempted; there were bound to be problems. Next year will be better. And the least terns are still doing okay this year; there’s still hope. After all, there was no electric fencing last year and the least tern colony at Quonnie Beach still fledged 111 chicks.