Posted in Petit Manan 2016, tagged Arctic Terns, Butterfish, Climate Change, Common Terns, Fish, Fish and Wildlife Service, FOMCI, Gulf of Maine, Hake, Herring, Lumpfish, Maine Coastal Islands NWR, Ocean Warming, Overfishing, Petit Manan Island, provisioning, Sandlance, Stickle-Back on July 25, 2016|
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Recently on Petit Manan Island we have been conducting chick provisioning studies. The purpose of these observations is to determine what prey species are being fed to tern chicks in order to see how prey composition is related to tern chick survival rates. We also record the time of the feedings, which chick is being fed, and the size of each prey item. Over the last decade the fish diversity on Petit Manan has increased. Although it allows us to see new and exciting fish species, it is not a positive sign for the terns. Increased feedings of invertebrate species such as moths, dragonflies, and other insects are also not great signs. Invertebrates and some fish are not as nutrient rich as herring and similar fish species, making them less beneficial for tern chicks. In 2006, common tern feedings consisted of 95% herring. Data from more recent years show that herring has dropped to 25% in 2010 and 34% in 2013 for common terns. Other fish species, such as hake and sandlance, have increased in feeding frequency. Although we do observe feedings of herring, hake, and sandlance, a large proportion of the feedings have consisted of tiny invertebrates and low quality fish species. Throughout the summer we have seen a total of 14 fish species, two aquatic marine invertebrate species, and at least 2 terrestrial invertebrate species being fed to chicks.
Herring and Hake, respectively
Species like butterfish, lumpfish and three-spined stickleback are not high quality prey items because often tern chicks are unable to swallow the fish. Butterfish are disc-shaped, and often they are too wide for chicks to swallow. Lumpfish are a rough, round fish species that chicks can only eat when the fish are very small. Sticklebacks, as their name implies, have spines on their back that catch in the chicks’ throat when being swallowed. We often find them uneaten near nest bowls.
View from Chick Provisioning Blind
Some of the factors that are believed to be causing these changes in fish composition are ocean warming and overfishing. Over the last two years ocean warming has been affecting seabird populations on both the Atlantic and the Pacific Ocean. Seabirds are indicators of marine ecosystem health. Tern breeding pairs have been decreasing on Petit Manan Island for at least the past seven years, and this season marked the first time the total count of tern nests dropped below 1,000. As recently as 2009 Petit Manan was home to 2,500 pairs of terns. This could be indicating that the food availability in the Gulf of Maine is failing, and the terns are not able to find enough prey to be able to reproduce after their migration. To get a sense of what prey species are available to seabirds, we can use our provisioning data as a sample of the prey availability in the waters around Petit Manan Island. Also we can look at provisioning data to see how the rapid warming of water in the Gulf of Maine is affecting prey populations; in particular the herring population.
Using data from all of Maine Coastal Islands NWR and Project Puffin islands, we can learn what is happening in the Gulf of Maine system. This data will assist in monitoring the effects of a warming Gulf of Maine on the marine food web and what this means for the future of our seabirds and fisheries in Maine.
Butterfish and Three-Spined Stickleback, respectively
I have really enjoyed doing these studies because it is exciting to watch the chicks’ daily activities and often the time goes by quickly. For our provisioning studies, each person has a blind that they spend time making observations from every other day. Returning to this specific area every other day is a great way to allow us to see the progress of the chicks and allows us to get to know each chick’s habits. These studies also allow us to see many different fish species as the terns bring them to feed their chicks. This is another great part of the job because it helps us work on our fish identification skills.
-Jimmy and Jill
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Posted in Metinic 2016, Uncategorized, tagged 4th of July, developing feathers, Great cormorant, Lesser yellowlegs, Maine, Metinic Island, Northern fulmar, Productivity, provisioning, Semipalmated plover on July 4, 2016|
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Hello everyone! The main focus on Metinic this week was our chick provisioning watches. Essentially what happens is we are watching to see what the adults are feeding their chicks. To set this up, we select a number of nests in good visibility from our blinds and mark them with numbered and color-coded tongue depressors. We then find the chicks that belong to each nest, band them, and then color a specific part of their body according to the hatch order and corresponding nest. The first chick to hatch is called the “A” chick and is colored on top of its head. The second chick to hatch is called the “B” chick and receives color on its chest. The third chick to hatch is called the “C” chick and is colored on its back.
One of our provisioning nests. The color on top of the “A” chick’s head corresponds to the color on the tongue depressor. When the egg hatches, the “B” chick will get the same color on its chest.
During each provisioning stint we watch each nest for adults coming in with food for the chicks. We record the nest number, the arrival time of the adult, which chick receives the food, the departure time of the adult, the number of prey items, and the species of prey brought in and its size. Prey size is determined based on the bird’s bill length. For example, a fish can be recorded as 1 bill length or 1.5 bill lengths; size is measured to the closest quarter of a bill length. All of this is often determined within a few seconds as the adults swoop in and the chicks gobble down the food quickly. Each provisioning stint lasts 3 hours and we try to total at least 12 hours a week each. All of this information will give us an idea of the amount of food coming in and its quality.
Besides the provisioning watches, we have also been continuing our productivity monitoring. It is amazing to see just how quickly our chicks are growing up! Right now the majority of them are in the process of replacing their downy fluff with feathers. Another interesting thing to observe is the range in development. A few of the chicks have mostly feathers and seem like they will be fledging soon, while others haven’t even hatched yet!
One of the older chicks in our productivity plots showing off its feathers. It is getting so big!
Provisioning and productivity take up the majority of the week, but Mark and I decided to take one afternoon to head down to the southern end of the island to see if we could spot any new species to add to our island list. As we were walking along one of the southern cobble beaches we came across a bird washed up on shore. At first glance it looked like a small gull, but as we got a closer look we discovered that is was a tubenose. Upon further observation and investigation, we were able to ID it as a Northern fulmar! Our species list is now up to 92 with the addition of a great cormorant, lesser yellowlegs, and a semipalmated plover!
That’s about it for this week, we will be celebrating the 4th of July with our seabirds! So far, we have been enjoying the various firework shows going on miles across the water on the mainland, and who knows, we may even break out the small grill this evening!
Have a happy 4th of July!
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…And breakfast, and lunch! For four days every week we each perform a “provisioning” stint of three hours. During provisioning stints, we observe our selected 5-7 nests of chicks to see what their parents are bringing them to eat and how often each chick is getting fed. We record the prey type, the size of the prey in comparison the to adult’s bill length, which chick from which nest is getting fed, and the time of the feeding. Charlie has been watching 6 Arctic Tern nests, with a total of 6 chicks, and Jennie has been watching 6 Common Tern nests with a total of 12 chicks! You cant leave the blind during a provisioning stint, so if you need to pee it means taking a trip to ye ol’ coffee can…
Common Tern Provisioning nests (Orange Flags)
In order to tell all our chicks apart we color them with markers! Each nest is a different color, and then if there is more than one chick in the nest, the first born chick (the A chick) gets colored on the head, and the second born chick (the B chick) gets colored on the breast. It is quite entertaining to watch little brightly colored chicks run around!
Two Common Tern provisioning chicks. The purple head denotes an "A" chick, and the purple breast is the "B" chick.
One of the big challenges of provisioning is to correctly identify the fish species. This can be difficult since some of the feedings happen extremely fast! Those chicks are hungry! Some of our common fish are Atlantic Herring, Butterfish, Pollock, Sand Lance, Hake, Needlefish and a variety of invertebrates. From our observations, we can analyze the chicks’ diet composition and feeding rate.
A Common Tern with a Pollock
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