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Archive for June 1st, 2019

Good evening everyone!

Nesting is well under way here on Metinic. While all the terns are pairing up, it is possible to see a few that are trying to be the envy of the whole colony. How you might ask? Well they flaunt some forage fish of course!

I enjoy watching as a tern will bring a fish onto the point and move all over the place, showing it off to as many other terns as possible. They really know how to make their neighbors jealous!

Forage fish are the main food source for terns. What are forage fish exactly? Well they are species crucial to the connection of the marine food web. Sometimes referred to as “Wasp-waist” species, these fish connect the abundance of zooplankton and phytoplankton in the ocean to the abundance larger predatory fish. Basically forage fish eat the small stuff (zooplankton and phytoplankton) and then larger fish (and seabirds) eat the forage fish. Without forage fish, there would be a large gap in the marine food web.

Monitoring forage fish species that the terns are bringing to their chicks will be crucial once they hatch. A few years back, there was a low abundance of Atlantic Herring (their favorite food), and instead a large abundance of Butterfish. The only problem was that the tern chicks were not capable of swallowing the Butterfish. Despite the large abundance of fish, sadly many tern chicks starved that year.

In recent years, especially in Maine, forage fish abundance has been a widespread issue. Outside of the seabird world, Atlantic Herring and other forage fish are used by people in various ways. However, the most common use for these fish is as bait, especially for Lobster. Many Lobstermen will tell you that while there are other baits that work, Atlantic Herring works the best as lobster bait. That has created a competition between Lobstermen and the seabirds for herring.

There are several papers that have been posted on the important role that forage fish play in seabird producivity. However, one paper has rung true for many seabird species across the globe. The motto of that paper is “One third for the birds”. Basically, one-third of the maximum prey (forage fish) biomass should be saved for the birds to consume. Increases in human uses of forage fish has made this a complicated situation. If you would like to read the paper for yourself here is the link: https://archimer.ifremer.fr/doc/00056/16770/14307.pdf

With all that being said, fish are key to seabird survival! Therefore we need to monitor which species the terns are bringing back to their chicks. (There is a whole other rabbit hole to go down about how we can use seabirds as indicators for the health of fisheries but I’ll save that for another time).

By the way, I have marked a total of 25 eggs so far, with 6 nests identified as Arctic Terns and 5 as Common Terns (one of which has 2 eggs!). I am hoping to have the rest of the nests marked by species in the next few days.

All the best,

Mary

(Photo below: Common Tern with Hake)

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(Photo below: Common Tern with Hake)

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