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Posts Tagged ‘seabird conservation’

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(A few of our first of hopefully many eggs on Ship!)

Hi folks!

Bobby from Ship Island here, as the cleverly constructed title suggests, we have eggs here on the island! A total of 13 eggs in 12 nests, which gives us hope that the birds are willing to nest for the breeding season on the island. Whenever Colin or I find a nest with an egg, we turn the egg to stand up, that way when we check the egg later on we can tell if it has been incubated (the egg falls back on its side from the tern sitting on it) or if it has not (egg is still standing up).  However, the number of terns that have been showing up since the last blog post has not been ideal. We have not seen more than 50 terns at once on the island for the past week and a half, at this time last year for contrast, there were 519 breeding pairs. It has become crunch time as we are using our final method to attract the terns back, creating our own tern colony.

This is done with two simple props, audio of a tern colony through multiple speakers, and using wooden decoys of terns (bird manikins essentially). These both simulate that a real colony is on the island and that it is safe to nest for the breeding season. Although it reminds me of The Truman Show in some ways, this method is the best bet to have the terns stay and nest immediately to allow them to be raising young in time for their migrations later in the summer. To paraphrase Princess Leia from Star Wars, the tern decoys may be our “only hope left”, but Colin and I are waiting confidently for our feathered friends to return. Don’t stop believin’ in Ship Island!

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(Terns and the decoys, can you spot the difference?)

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This past week on Ship Morgan and I both took our short breaks off the island. While Morgan was away I was joined by Kelby from PMI to work on predator control, productivity plot management, chick banding, and more!

We’re starting to see more and more chicks every day! Usually when we’re checking the productivity plots we can see when they start pipping. This is when their little beaks start to break open the egg. This lets us know that the next day we will definitely have some new arrivals to weigh and band if they’re dry and ready.

Before we start provisioning, we still have some time to re-sight birds from previous years. Typically, they will have a small silver BBL band on their ankle which contains either 8 or 9 numbers. We can use a spotting scope to see these numbers and enter them into a database where we can learn more information about that bird, such as it’s age. To make re-sighting easier, we put up posts for them to perch on so they aren’t being covered by the vegetation and are closer for us to see. While I was re-sighting from the blind, I spotted a tern that hasn’t been re-sighted in 19 years! I also found one with an orange band. This means that it was banded all the way in Argentina, which I thought was pretty cool.

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An example of a BBL band that can be found on the leg of a Common Tern. As you can see they are very small, which makes them difficult to read.

Now that the owl is gone, we are starting to see more birds come back to the colony. Many of them left during the time he was here and abandoned their nests. Thankfully now they’re starting to scrape the ground and re-nest. Chick age distribution around the island will surely be scattered, but at least they’re not giving up!

Now that I’m back on the island, there’s a lot more chicks running around and much more work to do!

-Amanda

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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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