For the past few weeks, a lot has been going on with Petit Manan’s tern colony! We have been focusing much of our time on trapping and banding both Arctic and Common Tern adults, which is an essential part of our research.
In order to capture terns, we use two types of traps—the bownet and treadle trap—to catch adults on their nests. First, we temporarily remove the eggs from the nest so that the bird does not crush its eggs if it struggles in the trap. The real eggs are replaced with painted wooden ones, and a trap is set over the nest. Trappers then hide out in a blind and wait for terns to return.
The bownet is a spring trap that is set behind the nest cup and triggered when the adult sits on two monofilaments stretching over the “eggs.” This trap has a metal frame and netting which springs harmlessly over the bird to contain it. The treadle is a small cage trap with a door, which the tern must walk through to trigger its closing mechanism.
a Common Tern being removed from a treadle trap
When a tern is captured, a researcher runs out from the blind to retrieve it and replaces the fake eggs with the real ones. Each tern receives a metal band with a unique number on one leg. Every Arctic tern also receives a field readable band with an alphanumeric code on the other leg, so that it can be easily resighted from a distance. We take several measurements, including mass, wing chord (wing length), and head/bill length before releasing the tern.
Julia banding an Arctic Tern
Wayne releasing an Arctic Tern
By banding these birds, we can learn about their migration paths, longevity, nest site fidelity, and productivity. Banded birds may be re-trapped or resighted in the future. If a banded bird is found along its migration path or on wintering grounds, we can learn about where it has been travelling. If a bird that was banded as a chick is later found as a nesting adult, we know that it has lived to breeding age and laid eggs. Speaking of chicks…
first Common Tern chicks hatched on 6/20
first Arctic Tern chicks hatched on 6/22
We found our first tern chicks of the season on June 20! Every day we are finding more chicks, and banding them as well. As the season continues, we will be closely monitoring their growth, survivorship, and diet to learn about the colony’s overall health. Stay tuned for more posts about these little cuties!