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Posts Tagged ‘Gulf of Maine Seabird Working Group’

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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We are packing our gear and cleaning the cabin!  Jennie and I head back to the mainland today and we wanted to give you one last update on our season.

We crossed off each day after we finished the dinner dishes. Its wild to think that its all over for 2011...

Census

The Gulf of Maine Seabird Working Group (GOMSWG) census was started on June 17, 2011, and finished on June 20, 2011.  The Tern nest count for the census was 484, with a Lincoln Index of 1.029, resulting in a corrected total of 498 Tern nests on the North End of Metinic.  This represents about two thirds of last year’s population.  Common Tern nests were marked with a blue flag, while Arctic Tern nests were marked with a red flag.  On the NE Point we identified 307 of 498 nests (61% of NE Point colony).  We counted 122 ARTE, 185 COTE nests.  We estimated that the colony was comprised of 40% Common Terns, 60% Arctic Terns. The South End of the island is privately owned and was surveyed by boat, 2 pairs of Terns were present, but no nests were confirmed.

Productivity

Fledging/reproductive success was low this year for Arctic Terns (under the 1 chick/nest USFWS goal), but Common Tern productivity improved from last year and met this goal.  The Arctic Terns suffered from widespread predation events early in the season which resulted in the loss of many eggs and young chicks.

Provisioning

We were able to follow 6 Common tern and 8 Arctic Tern nests throughout the season, for a total of 96 observational hours and 599 feedings. COTEs fed at an average rate of 1.6 feedings/hour, while ARTEs fed at 0.7 feedings/hour.  Both Arctic and Common Terns delivered Atlantic Herring most frequently to their chicks consisting of about 55%and 30% of their diet respectively.  Butterfish was the next most frequent delivery for both species, making up about 30% of deliveries.  Herring deliveries gradually declined and butterfish deliveries gradually increased as the season progressed.  Feedings overall slowed considerably starting in the third week of July especially for Arctic Terns.

Guillemots

32 Guillemot nests were located with a hatch success of 62% and an egg depredation rate of 12.9%.  This data is not a complete set because of the number of guillemots incubating through all checks.  Three adults were still incubating at the end of July, so hatch success could be higher than calculated. 19 chicks were found and 14 were banded, weighed, and measured.

Petrels

53  Leach’s Storm-petrel burrows showed signs of activity (smell, fresh piled dirt, activity at night) early in the season, however only 7 were noted to have eggs or adults present at the end of July.  At the end of our field season, 17 burrows were no longer active and 29 still showed some activity yet nothing could be seen with the burrow scope.

Common Eider

Eider numbers were very low this year averaging only 50-100 eiders at each morning count. Previous years Eiders had averaged between 150 and 300 for morning counts.  Only 30 observations of eider crèches were documented (at least 4 separate crèches).  Five eiders were banded by USGS and MDIFW.

Incidental Sightings

Species highlights: Northern Gannett, American Oystercatcher, Razorbill, Atlantic Puffin, Whimbrel.

We had a tremendous amount of fun out here this summer, and we hope you all enjoyed being able to follow along!  If we peaked your intrest and you would like to get involved or support our efforts makes sure to check out the Friends of Maine Seabird Islands site: http://maineseabirds.org/html/home.html!

Signing off!

-The Metinic Crew

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