The international shearwater

18 12 2015

Last week, the Science Club at Northern Essex Community College in Massachusetts had a special guest at their meeting. A world traveler joined us, having a last known address in Tenerife, in the Canary Islands. The visitor was a bird, and was, unfortunately dead.

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Here we are doing the dissection. 

This specimen was a female Cory’s shearwater (Calonectris diomedea) and we received it via Friend of SEANET Susannah Corona, who conveyed it to me in a sketchy roadside exchange. The bag containing the carcass did sport a jaunty holiday bow, however.

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The bit of bling carried all the way across the ocean.

Susannah found the bird on a beach north of Boston and managed to track down the banding lab in Europe with the info on it. Turns out, the bird was one of many confused by, or attracted to, the city lights in Tenerife where it struck a building. The bird was rehabilitated and banded prior to its release. Arantza Leal Nebot, a researcher with SEO BirdLife, provided us with this map of band reports. If my Spanish is even somewhat passable, then the blue dots represent where birds were banded, and the small red diamonds show band recoveries. As you can see, Susannah’s find was only the second North American report for a Cory’s ever in this project!

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The findings on necropsy were limited since the bird was rather decomposed. There were a few rib fractures sustained after death, which is consistent with being buffeted around by waves. That, in combination with the decomp suggests that this bird floated around a while after dying and only later washed up. I was able to determine that the bird was emaciated at the time of its death with no fat stores remaining in the body and substantial muscle wasting. The gizzard was empty but for a few squid beaks, and we found no plastic pieces in the GI tract. We often find plastic in shearwater stomachs, though I tend to find fewer or no pieces in birds that appear to have starved to death. It may be that birds who can’t find any food to ingest also aren’t ingesting plastic. This would suggest that the birds tend to pick up the plastic incidentally while feeding rather than mistaking the plastic for food, but that is mere conjecture on my part.

The Science Club students found our dissection day quite rewarding, and we plan to do it again next semester with whatever cool specimens we manage to wrangle up. For my part, I always enjoy a necropsy, but the rewards of introducing students to the interiors of seabirds have given me a new jolt of enthusiasm for the activity. Stay tuned for more such cases next semester when Science Club is back in action.

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2 responses

18 12 2015
Edward

Calonectris diomedea is presently the name of the Scopoli’s Shearwater from the Mediterranean. This one from the Boston beach will be C. borealis, the true Cory’s Shearwater from the Atlantic which can be found on the Azores, Madeira, Canaries and a few other locations. The map shown here mixes both species (formerly considered subspecies of C. diomedea) and shows that Mediterranean birds tend to migrate to South African waters and Atlantic birds also cross the ocean to North and South America.
Nevertheless a great find.

29 12 2015
scourc01

We suspect the bird died somewhere out at sea and was merely borne up here on the currents. It was rather decomposed, and given the strangeness of its turning up near Boston, we doubt that it arrived there under its own power. Thanks for the species info–we have reported only what the banding folks told us as to species, and they maintain it is a diomedea, so I will clarify with them since it appears they must mean this was a Scopoli’s. Will see what they say!

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