Archive for July, 2011

A Common Tern productivity plot

One of the big projects that take place on many seabird islands in Maine is productivity monitoring, or seeing how many chicks survive to fledgling age. For the Gulf of Maine Seabird Working Group, fledging age is 15 days old for Tern chicks. To monitor productivity, we take a sample of the colony and fence off about 10% of the nests into small plots. These plots allow us to contain the chicks and to find them day after day. We have 5 plots; two Arctic Tern plots, and 3 Common Tern plots. These contain 59 nests in all! The number of Arctic and Common tern nests in our plots correlates to the overall species ratio for the colony.

Jennie banding a chick

Everyday, we go through our plots to check the progress of eggs and chicks. When chicks hatch, we band them so the next day we will know which chick is which, or which one has hidden from us.

We also weigh chicks so we can get an idea of how fast they are growing. Chicks can start out weighing as little as 10g, but one Common Tern chick started at 26g and is now 46g only 6 days later!! It is amazing how quickly they grow!

Charlie weighing a chick

At the end of the season, data from our productivity monitoring will be used to calculate a survival rate and growth rate for chicks. This can then be compared to other seasons. Last year, on average, Common tern pairs fledged 0.85 chicks per nest, and Arctic Tern pairs fledged 0.32 chicks per nest. Common Terns usually do fledge more chicks per nest because they have a shorter migration. This allows them to invest more energy in chick rearing. It will be interesting to see how this year’s rates compare to last year. We are very excited to watch our chicks grow a little more each day! We can’t help feeling like all these chicks’ Aunt and Uncle!

On a side note… We spotted an American Oystercatcher today! This was a rare sighting since the Oystercatcher’s breeding range is typically only into Southern Maine. We are a little too North for this to be a common sight. Sorry no pictures, it was at a distance!

Have a great 4th of July weekend!

~The Metinic Crew; Jennie, Charlie, and special guest Brian Benedict

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