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.





DBQ answers II

14 12 2015

No more shirking or dodging; I must at last face those wings known as Bird B. To jog your memories, here’s what we’re working with:

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Dennis, who found the wing, wondered if this might not be something other than a standard issue species. Everyone who has looked at the wing (and ventured to reply) concurred that this is a loon of some kind. The clean white underwing by itself could indicate a few different species groups, including shearwaters and grebes. But looking at the upper wing, we see buff colored chevrons at the terminal ends of the secondary coverts. The wing chord looks to be around 28cm. These features together tell us this is a loon, and a pretty small one (common loons have a wing chord in the 33-40cm range). Red-throated loon is the default i.d. for a small loon on the east coast, but it’s not the only possibility. Dennis granted that it could certainly be a RTLO, but thought something just seemed a bit off about in terms of its overall coloration and the nature of those pale chevrons. Since Dennis has seen many, many a dead bird, I think it worth a look when he notes something atypical about a carcass. Dennis thought perhaps Pacific loon should be on our consideration list. If we consider Pacific, we should also consider Arctic since the two are almost always uttered in the same breath and can be difficult to distinguish themselves. Both Arctic and Pacific loons would have a wing chord in the range of Bird B’s; both average larger than RTLO, but a wing chord of 28cm would fit with any of the three species. Strangely, given what one might assume from the names, the Arctic loon would be much more of a rarity than the Pacific in these parts.

This situation calls for the use of two of my favorite resources: Peter Pyle’s identification guide, and the Slater Museum’s online wing collection. You can check out a whole suite of loon wings from various species and times of year here. Fortunately for me, they have a few Pacific loon specimens there to look over, in breeding and non-breeding coloration. As with many loons, breeding plumage includes bold, clear, pure white spots on otherwise black upper wings. Our Bird B does not have any white spots or dots at all, but that lack is typical of a bird no longer in nuptial raiment. Beyond being a non-breeding bird though, what we have here in Bird B appears to be a young bird. In the case of RTLO and Pacific loon, both have pale edges to the secondary coverts during the first year, and that first year plumage is retained into well into the first winter, so the timing is right for Bird B, which was found at the end of November.  To parse out the differences between juvenile RTLO and Pacific loon wings, we can look at Peter Pyle.

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Secondary coverts in Pacific loons. In juveniles, a pale, terminal band gives the impression of light, nearly white crescents over the upper wing.

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Contrast the preceding with these secondary coverts from RTLO. The far left image is a juvenile and the pale coloration here is much narrower and comes to more of a point, giving an impression of chevrons rather than crescents.

Considering this, I am of the opinion that Bird B is decidedly chevroned and now crescented. And so, though I had fervently hoped we might have a first ever Pacific loon in our database, I fear it is not, and is, instead, our old friend the Red-throated loon. As ever though, if I am missing something critical, I know all you super-pros will write it with the correction.





DBQ answers

9 12 2015

Let us address Bird A, who met a bad end (and a Cessna) at 3,200 feet. The head was torn off by the force of the impact, and, left with only the feet and legs, and a bright white belly, we must make this i.d. without the benefit of a look at its back or upper wing surface. Some folks who examined the photos thought perhaps it was an oystercatcher, but looking at the feet especially, we can rule that out.

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Plane Bird feet

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Oystercatcher feet

Comparing the feet side by side, we that Bird A (Plane Bird) has a grayish cast to the legs and feet, with black coloration on the outside aspect. Bird A’s legs are also extremely flattened side to side, with a very narrow front profile. (Compare the width of the side view of the right leg with the left leg which is rotated so we see it head on). This gives the leg a blade like appearance. The oystercatcher’s legs are more rounded, and the extreme lateral flattening of Bird A’s legs is a fair giveaway of what species group we have here, and rules out other black and white birds with more rounded legs (like the alcids). There’s really nothing but a loon that shows this lateral compression of the leg and even toes to such an extent. It’s hard to appreciate the webbing in loons in many cases since their toes tend to fold together in a dead specimen. Take a look at this reference picture of a known loon and compare the features of the feet with Bird A, noting the color, the length of the three forward toes, and the extremely reduced hind toe in both specimens:

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common loon carcass (Photo by Gil Grant)

So the feet say loon, but what kind of loon? Our most likely suspects are common and red-throated (COLO vs. RTLO). Unfortunately, the best ways to distinguish the two are via features of the head and neck (absent here), the measurements (no size reference here), and the pattern of the feathers over the back and upper wing (not visible here). Can we make this i.d. to species with what we can see? Much as I wish otherwise, I do not think so. I was hopeful that something like the black stripe across the vent in Bird A might help, but take a look at these reference photos of various vents from various loons:

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RTLO with very faint dark line across vent. (Photo by Sarah Porter)

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RTLO with basically no vent line. (Photo by Jerry Golub).

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COLO with a fairly prominent vent line. (Photo by Dennis Minsky)

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There are cases (like differentiating Arctic from Pacific loons, apparently) where presence versus absence of a vent line can be your make or break feature. But for us, deciding between RTLO and COLO, it’s not much help. Either species can have a faint or a prominent vent line, so the fact that Bird A has a visible one doesn’t really tell us much.

Live birds flying overhead are sometimes the closest (ironically) we can get to the situation of trying to identify a dead bird from features of its undercarriage, and I refer you to such a case posted at the American Birding Association’s website here. In their analysis of that bird’s i.d., they point to a sense of how big the feet are relative to the body. Common loons have absurdly large feet compared with RTLO, whose feet tend to look more normally proportioned. You can appreciate this a bit when you compare the images above of the feet on RTLO vs. COLO. Which is true of Bird A? Huge feet, or not so huge feet? That’s a bit hard to tell from the angle we have. They seem somewhat outsized to me, but I’m not feeling super confident on that. Bob, who collected the bird from his plane’s wing, submitted feather samples to the Smithsonian for i.d. to species, so hopefully, we will receive word from on high for this one. Bob did email this week to say he has yet to hear from the Smithsonian. Perhaps we should run a letter writing campaign and on site protest bearing signs that read, “Who is Plane Bird!?”

I still have Bird B to address, but right now, I must run to pick up the kids. Next installment will be before your eyeballs later this week, I assure you.

 

 

 

 





DBQ: drama at 3,000 feet

3 12 2015

I had not intended to post a DBQ this week, but this one practically fell in my lap and I couldn’t resist it. This week, I met with Susannah Corona who conveyed to me the carcass of a shearwater with a remarkable history (but more on that in a coming post). The next day, she sent me an email with images of a dead bird that had originally been sent by a man named Bob Thomason, and then forwarded from biologist to biologist, looking for an i.d. Here is the partial text of Bob’s email:

“On Saturday November 14th, I was climbing out in my 6-seat twin engine Cessna northwest out of the Anson County (Wadesboro), NC airport when I struck a bird at about 3,200 feet above ground level.”

The bird was struck, and then the carcass apparently became lodged in the sizeable crater in the wing that the body made on impact and was still there upon landing, albeit without a head. Debate ensued as to the identity of the bird. I am certain you will know right away what it is, as the i.d. is not particularly tricky, but I felt good about this particular case since the shorebird biologists who looked at the image didn’t know. I am horrible at identifying shorebirds myself, so it was nice to know the feeling is often mutual, across the shorebird/seabird divide. Here are the remarkable images:

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In addition to the plane bird, I also got a note from Dennis Minsky out on Cape Cod about a wing he’d found, and whether or not I agreed with his i.d. So of course, I am crowd sourcing that in order to see if you all concur with me. Here are the two shots of that wing. Please note how nicely Dennis arranaged the wing on the ruler so you can actually get an accurate wing chord too!

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Trying to keep my cool, readers,

5 11 2015

but I just spent two hours on my DBQ answers post, then my browser crashed, and it all disappeared into a black hole, evidently. You can, I am sure, imagine my frustration. When I can regain the will to go on, I will try to recreate it all.

Sigh.





Dead Bird Quiz, late for Halloween

2 11 2015

Ghosts and goblins and zombies have nothing on actual dead things, of course, so Halloween is naturally the holiday for SEANET. Perhaps that’s why I was too busy last week to post to the blog at all. Out celebrating.

In any case, you all deserve a DBQ. Here’s a three-fer!

Bird A, found in Maine, and submitted by Barbara and Charlie Grunden:

Dorsal surface.

Dorsal surface.

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Ventral surface. Or, it was at one time.

Bird B, found by Dennis Minsky on Cape Cod early in October:
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Bird C, found by Warren Mumford, also on Cape cod:
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Statelessness and decline in seabirds

23 09 2015

This week, I read an article in the Guardian about global, severe declines in the majority of seabird species. The impacts have been worst in open-ocean birds like albatross, petrels, and shearwaters. Though the causes of such a broad and precipitious decline are myriad, one particular factor caught my eye–the remarkable globe-trotting of these birds and their utter lack of respect for political boundaries. People marvel at feats like the globe crossing migrations of terns, or the zig-zag path of Greater Shearwaters as they bounce from North America over to Africa and down to the farthest south Atlantic. But this fligth prowess puts there birds at risk. While they may be well protected under one nation’s conservation policies, as soon as they pass into another country’s waters, those protections may fall away. This is not to mention the lawlessless of the high seas–the open ocean where many of these birds must make a living. Plastic pollution, overfishing, entanglement: these mutiple factors all converge on the open ocean species.

In my biology classes, I like to show my students, many of whom are immigrants from the Dominican Republic, this image of the island of Hispaniola.

The border between Haiti (left) and the Dominican Republic (right) where forest protections are much more stringent.

The border between Haiti (left) and the Dominican Republic (right) where forest protections are well enforced.

In many cases, we know what we need to do to protect seabirds; longline fishing techniques, for instance, can be modified to avoid catching albatross. But issues of compliance and enforcement are myriad. We know that overfishing can be addressed and that fish populations can rebound quickly in some cases. Several years ago, Senegal banned the export of fish caught in its waters and rescinded the fishing licenses of many EU and Asian boats. This was done mainly to protect subsistence and artisanal fishing in that country, but it has successfully boosted fish stocks. Each nation makes its own laws, of course, and even then, the ability to enforce those laws varies wildly between nations and continents. Threading their way through all these borders are the seabirds. Unless we can get some semblance of an international approach, it seems we can anticipate further declines across these species groups. I am congenitally optimistic, but my realist side does wonder…








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