One of the important questions that the research team on Petit Manan tries to answer each season is what the growth and survival rates are of the tern chicks on the island. There are over 1,900 tern nests on almost every surface of the island—the rocky shoreline, in amongst the vegetation, and even on the lawn around the lightkeepers’ house that serves as our research station. Each nest usually contains between one and three chicks.
Up to three chicks times almost two thousand nests… that’s an impossible number of chicks to keep track of! In order to keep our monitoring effort reasonable, and to reduce the impacts of our presence in the colony, each year we set up roughly 10-12 productivity plots. These are basically tern playpens, each of which contains 5-15 nests. The temporary barrier that we set up at each prod plot allows us to consistently monitor a subpopulation that will be representative of the whole island.
Every day we record the number of eggs, pips (eggs that have begun to hatch), and chicks we have in each nest at every productivity plot. We also weigh each chick and put a metal identification band around one of their legs so that they can be resighted and identified for the rest of their lives.
We try to check each plot as quickly and efficiently as possible so that we don’t stress the parent terns for very long, but it can be quite a challenge because tern chicks are really good at hiding!
The data that we collect about the chicks’ growth and survival, along with information that we are gathering about the frequency and species of fish feedings (provisioning) will help us paint a more complete picture of the success of Petit Manan’s tern colony. We’ll have more information about provisioning in an upcoming blog, so keep checking in!