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Posts Tagged ‘Common Terns’

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.

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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.

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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.

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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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Petit Manan Island is in peak hatching season! The small, delicately speckled brown tern eggs are disappearing and being replaced by similarly patterned fluffy chicks. The oblong, white-brown spotted black guillemot eggs are opening up to reveal all-black downy chicks. Where once we were seeing large, gleaming white puffin eggs, now chicks with long grey down and white bellies are hiding quietly in their burrows. We even have found one razorbill chick (see photo below)! The only seabird still solely in the incubation stage are the Leach’s storm-petrels.

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One question that I often get asked is, why do some seabirds only ever hatch one chick (think puffins, razorbills, storm-petrels), while others can rear multiple chicks (terns, guillemots, etc)?

In general, seabirds have small clutch sizes compared to birds of other groups like most waterfowl, game birds, and some perching birds. This is because seabirds, unlike the groups mentioned previously, tend to have long life spans. This means it is not quite as critical for seabirds to have a successful nesting season their first breeding season or every year of their life in order to replace themselves in the population. Other bird species may only get one chance to successfully reproduce if annual adult survival is low due to high depredation of adults and/or other factors.

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But why lay only one egg instead of two or even three? There are multiple factors that influence seabird clutch size, and still many questions to be answered. Chick rearing is very energetically demanding for the parents, from egg formation to providing enough food for growing chicks. Right from when birds arrive on the breeding grounds, food availability is critical. After long migrations or rough winters, seabirds need to be able to find enough resources near their breeding colony to allow them to be in proper condition for breeding. Limited food resources during this period of time can cause birds to lay smaller clutch sizes, or even not nest at all.

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This still does not answer our question why puffins and other species only lay one egg, in both good and bad food years. For species with one egg clutches, it is more beneficial for the long-term survival and breeding success of the adults to raise only one chick at a time. Raising two chicks would probably not be impossible during good food years, but the energetic costs on the parents might make this not worthwhile in the long run. So puffins, razorbills, and many other seabirds prefer to take things slow, laying only one egg per season.

Currently, we have found 17 black guillemot chicks, 15 Atlantic puffin chicks, one razorbill chick, and a few hundred tern chicks!

-Jill

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Hey folks! Jill and Morgan here! It’s been a surprisingly beautiful first week on Petit Manan Island; let’s hope it’s a sign for the whole season! The island has been lively thus far with approximately 200 prospecting Common and Arctic Terns, but we’re expecting many more to come! Although PMI isn’t the largest of islands, it still receives a good deal of visitors, especially early in the season when birds are migrating North – we’ve seen 61 species thus far! Not all our guests have been of the bird variety though; we also stumbled upon a juvenile Grey Seal on our rocky shores earlier in the week!

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Downy Woodpecker sighting!

The start of the season means preparing the island for all the work to be done in the months ahead. This means setting up observation blinds, for band resighting and future monitoring of foraging habits and chick health, as well as collecting marine debris, building burrows for Black Guillemots and Atlantic Puffins, and marking potential Leach’s Storm-petrel burrows. Daily Alcid counts from the top of the Petit Manan Light have also begun. On a windy day it can get rather cold up there, especially for Jill, who hasn’t quite gotten used to the Downeast summer having just returned from a seabird job in the Galapagos!

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Can you spot the Leach’s Storm Petrel burrow? We’ve been searching the island for these small holes in the ground this past we week, and we have found 170 potential burrows!

As we prepare ourselves for the research season ahead, the birds are doing the same. The puffins and guillemots are seeking out rock crevices and other sufficient and creative hiding spots for their burrows. The male terns are attracting their mates with a Sandlance dowry. The Common Eiders are seeking out areas of high vegetation to form their nests. And the Peregrine Falcons, Merlins, and gulls lurk about hoping to catch a bite to eat with all these new dining options in town.

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The Atlantic Puffins have already begun choosing burrows!

Till next time, here’s a joke to hold you over – Why did the Puffin have a stomach ache? Because it had Alcid Reflux!

Best,

Morgan & Jill

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Little white and silver flecks moving through the sky like leaves dancing in the wind. Twisting and turning, colliding and winding, at first glance they disappear with the dark blue of the water.  But with a simple turn, the setting sun light reveals them, and they emerge from the dark backdrop of the water and glow a bright slivery-white. These little slivery-white flecks were terns flocking over the ocean the other night. We were lucky enough to have witness this as we were up on the light house enjoying the sunset. This event went on for about five minutes and almost every tern on the island was participating. It was a foreign feeling to have the island quiet of terns. But the ocean was a roar with the commotion they were making. This flock was the most terns we saw on PMI so far this spring. As we predicted, more terns came to PMI that day and were flocking to strengthen the colony and welcome the new arrivals. We hope to have more arrivals like this as spring progresses.

-Laura Bollert

Photo by Wayne MacCabe

Photo by Wayne MacCabe

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Hi there!

I’m Meaghan. I’m a fourth year wildlife ecology major at the University of Maine at Orono. This is my first summer living and working on a seabird island, and I am very excited to be able to do so! Last summer I worked as an intern at the MCINWR visitor center in Rockland. While there, I had the opportunity to visit several of the seabird islands and very quickly ‘caught the bug’ for island life and could not wait to get out here myself.

Working as my supervisor is Derek. He is a fourth year environmental geography major at Central Connecticut State University. He is a Rhode Island native who has a lot of experience living and working on seabird islands in Massachusetts. However, this is his first year working with MCINWR on a Maine seabird island.

Our home for the summer (Picture: Meaghan Hall)

Our home for the summer (Picture: Meaghan Hall)

Our first week on the island was a lot of fun!

The first couple days were spent settling into our new home and familiarizing ourselves with the island. We conducted a sheep round up in order to move the sheep, that graze across the island during the off-season, off of MCINWR land so they do not disturb the seabirds during the nesting season. We have also been walking the island checking for and collecting garter snakes. In previous years these snakes have been observed preying on tern eggs and chicks, so we are trying to exclude them from the seabird nesting area. Lastly, we have been conducting morning bird counts. So far we have observed 31 different species of birds, including some migrants along with Common Eiders, Black Guillemots, Double-Crested Cormorants, and Spotted Sandpipers.The flock of Arctic and Common Terns that nest here annually have been observed visiting the colony in the morning hours and leaving around noon – presumably to look for nutritious fish. We were also pleasantly surprised to observe two Rosette Terns visiting our island! We are hoping that the terns will settle in the colony within the next week and lay their first eggs shortly after that.

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Common Eider (Picture: Meaghan Hall)

Black Guillemot

Black Guillemot.  (Picture: Meaghan

We are very excited to be working as the technicians on Metinic this year and are more than happy to keep you updated on all things seabirds throughout the season!

-Meaghan and Derek

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Rose and Mary here with a quick blog before the last sunset of our summer on Ship Island.  It has been a wonderful time and we are both leaving here with many memories that we’ll keep for a life-time.  From finding the first common tern eggs

Literally our first egg found on May 28

Literally our first egg found on May 28

 

to our 4th of July grilling party with burgers, 2 pies, chips, cherries, and corn on the cob…

Rose preparing our all-out fourth of July "burgers."

Rose preparing our all-out fourth of July “burgers.”

to identifying a black skimmer after tropical storm Arthur (a somewhat rare species up this far north, typical after southern storms)….

Black Skimmer, Common Tern and Eider legs

Black Skimmer, Common Tern and Eider legs

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Common tern fledgling exploring the beach.

to watching fledglings fly and touch the water for the first time.

We have learned so much about common terns and island living.  As far as we can tell so far, without having computed our final numbers, our colony did very well this year.  While the peregrine falcon and merlin visited nearly daily after chicks hatched, they did not disturb the terns enough to affect the whole colony.  The larger of the storms down-poured over 3 inches of rain at times, yet miraculously we had very little loss due to the weather.  The Ship Island Common Tern colony is a prime example of a restoration island success story and it has been wonderful to be a part of this effort.  Thanks to the Maine Coastal Islands National Wildlife Refuge Staff for giving us this opportunity and for the amazing seabird restoration and management work that you do!

Hasta luego! (Until next time!)  Rose and Mary

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Last walk on the tern colony beach.

One of our last sunsets.

One of our last sunsets. Enjoy the rest of summer!

 

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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.

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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.

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Julia banding an Arctic Tern

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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…

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first Common Tern chicks hatched on 6/20

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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!

-Anna

 

 

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