DBQ answers

12 01 2016

I got quite a few responses to this one, and I am not surprised that our usual ringers were right in here with both the clear i.d.s and the one that is, at least somewhat, in question. All three birds are ducks which all respondents recognized. The first two are in one category–ducks with a bluish speculum on the wing. Bird C is in a category of ducks with blue on the wing, but with that blue located on the upper wing coverts rather than the secondaries as in Birds A and B. Let’s take the Bird A/B pairing first.

I like when I have an all duck quiz since I can use Samuel Carney’s Waterfowl Wing Key. When we follow through that key for a bird with blue or purple on the secondaries, we get to a junction point where we are asked what borders the blue or purple patch. If it is hemmed in with white both above and below (that is to say, with white on both the greater coverts and on the trailing edges of those blue/purple secondaries), then we have a mallard, like such:

800px-Mallard_pair_in_flight

Mallards in flight. (Photo by Ingrid Taylar)

In this photo, one can see not only the clearly bordered speculum, but another helpful feature for when you have the underside of the wing to look at as well–a mallard’s underwing is a clean, clear white. This is in contrast to our other candidate among the blue-speculumed ducks, the American black duck, which has a characteristic brown streaking on the underside of the wrist.

An American black duck (ABDU to friends) is generally described as having no white border, front or back, around the blue, though in many images and in some descriptions, one may see a faint pale trailing edge to the secondaries. It’s pretty faint though. Great, so that was easy, no? White borders: mallard. No white borders: ABDU. Not so fast (0f course). Because these two species heard we were having an easy time of their identification, they decided to hybridize freely. Given the slight chance of pale tips to the secondaries in an ABDU, we can look at the forward border of the speculum for a firmer sense of what is happening here. In an ABDU, there should be no white at all on the greater coverts at that leading edge of the blue speculum. So, where are we now with respect to Birds A and B? A shows substantial white both fore and aft. Bird A looks like a mallard decisively to me (my decisiveness here is augmented by back up from most of our respondents on this quiz). Bird B has what we might technically term a “meh” amount of white on that forward border of the speculum. It’s faint, but it’s definitely there. While some of our quiz players think ABDU on this one, others raised the possibility that this is one of those ABDU x MALL hybrids, and I am inclined to agree. Would that we had more of the bird to go on, but the features here do seem intermediate between the two species.

Now, to Bird C. This one is in the group of ducks with a large amount of blue on the upper wing coverts rather than the secondaries. It’s hard to know if the secondaries ever had much color–they may have, but as my next blog post will address, blues and greens in bird feathers are a trick of the eye, and in a disheveled specimen, those colors may be lost almost entirely. In addition, in some species, the secondaries are green and iridescent in males, but green and non-iridescent (dull) in females. I don’t see much that catches my eye in the secondaries of Bird C at all, but if there is any green there, I would say it looks decidedly non-iridescent to my eye. What we have to go on is the blue, and then some white on the greater coverts, though they do not appear entirely white–more dark spotted with white rims. In the group of birds with blue on the coverts and a white band on the greater secondary coverts, our best candidates are blue-winged teal and northern shoveler (both raised by our respondents). How to differentiate them? The number one feature all the field guides point to are the distinct white shafts of the primaries in northern shovelers. Take a moment to appreciate them in this image:

 

Screen Shot 2016-01-12 at 11.05.37 AM

USFWS photo

As you can see in these images, the white band on the greater coverts in northern shovelers is uninterrupted, unlike the broken band with dark spots we have in Bird C. In addition, I do not see these obvious white primary shafts in Bird C. Taken together, these two features lead me to call this a blue-winged teal, and again, I draw unnatural courage in this i.d. from the fact that it came to me pre-identified by Craig Watson who works for USFWS down south, and also, so many of our crack dead bird experts told me they thought it was a blue-winged teal as well. I hardly ever see these, so I confess, I would not have come up with that right off the bat.

Next time, I will share with you what I’ve been reading about feather pigment, honest signals, and the flamboyant tails of motmots in the Yucatan.

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Dead Bird Quiz: got the blues edition

8 01 2016

It’s a monochrome world outside here in the north, and, though I am secretly wishing for snow so I can get some cross country skiing in, I do appreciate a spot of vibrant color. Thus, I have made these selections for the DBQ. Though they are not the most challenging ever, this will give me a window to talk about pigment in feathers when the answers are revealed, so look for that next week.

Here are our candidates (a phrase I hear a bit too often for my liking here in New Hampshire these days; I can’t travel 5 miles without tripping over a would-be President).

Bird A: found by Dan Tracey in Massachusetts in May.

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Bird B: found by Ray Bosse, also in Massachusetts, also in May.

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Bird C: guest Seanetter Drew Lanham, professor at Clemson, photographed this bird on New Year’s Day on Seabrook Island, SC.

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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.

IMG_7742.JPG

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

IMG_7743

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 part two

11 11 2015

And now we return to the continuing saga of dead birds. Bird B, you will recall, was little more than a skull and some other odd bone bits. Remember Bird B?

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Responses as to the identity of Bird B were split between common eider and some sort of goose. Indeed, this is a waterfowl type of bill, with a sloping profile and some serrations on the bill margin. The profile is quite smooth from bill to forehead, with no knob or other protrusion anywhere along the bill’s length. This is our general impression when looking at the profile of a live common eider, especially since they have those fleshy lobes that run backward up over the forehead.

Note the fleshy lobes on the eider bill, more prominent in males like this.

Note the fleshy lobes on the eider bill, more prominent in males like this.

 

If you look at the skulls of eiders, which you can do at Wouter’s skull site here, you can see the bone structure that underlies those lobes in the rearward projections over the forehead. Our Bird Blacks these. The other respondents on this quiz listed various goose species as contenders, and to throw an additional bit of support for that into the mix, Dennis’ note when he found this bird noted that the wing bones seemed extremely large for a duck. But within the geese, which species? Responses included Canada goose, cackling goose, and barnacle goose. There is a bit of black and white feathering still adherent to the bones in Bird B, consistent with any of those three. Barnacle goose is far rarer in these parts than the other two, but not unheard of certainly. Cackling goose sounds like something unusual, until one reads a bit about it and finds out that cackling goose is the designation given to what used to be considered merely a very small race of Canada goose. Genetic analysis has determined that cackling goose is its own distinct species. Whether or not we can, from just a photo of the skull, determine if this is cackling goose or Canada goose is a dubious question indeed.

But within these geese candidates, now is the perfect time to send you over to Wouter’s Skullsite which is an absolutely marvelous resource that I know I mention often, but with good reason. If you refer to the Anatidae (ducks and geese) page of that site here, you can get a look at the comparison between barnacle goose and Canada goose. Barnacle geese in life have what we might term a “cute” face. (Cute being a highly technical term). We tend to find animal faces cute when they have outsize eyes for their faces, and if you look at the barnacle goose skull, you will see that its eye socket (or orbit) is quite large. Compare that with the size of the orbit in the Canada goose. I would argue that the overall shape of not just the orbit, but the squared off back of the skull in our Bird B as well as the length of the bill compared with the length of the skull all argue for Canada (or cackling) goose rather than barnacle goose.

Finally, we have Bird C, which presents a substantial identification challenge. Indeed, there is really not enough here to get us to species. Everyone responding figured we have a duck here, and I concur. Edward suggests there might be a tiny hint of a blue speculum, leading us perhaps to American black duck, but neither he nor I am entirely convinced of its presence. Wouter did want to venture beyond saying it’s a duck, Mark and Jim did not venture a guess (and I can’t blame them), and John Stanton took a stab in the dark and guessed Bufflehead. So how did people know this was a duck? Wouter points to the only real clue we have–the sternum.

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This affords us an opportunity to use another of my favorite sites, aves3d.org. Take a look at this image of a surf scoter sternum, rotated to reflect the same angle we have on Bird C:

Copyright Harvard Museum of Comparative Zoology and Aves3d.

Copyright Harvard Museum of Comparative Zoology and Aves3d.

There are substantial similarities here–the overall blocky shape of the sternum, the crescents cut into the rear facing edge, and the flared projections beside those cutouts. Similar enough to make a species call though? Maybe. Take a look at these comparative images of the sternae of some other ducks:
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Somewhat surprisingly, since the surf scoter seems such a close match, the black (or common) scoter is actually dissimilar to Bird C in many ways: the crescents are more pointed in the black scoter and there isn’t as much of a pinched in, hourglass shape the sternum overall. The common eider sternum beside it actually looks a bit more like Bird C, but here the lateral projections look a bit too rounded and blunted at the ends. I might actually be inclined to call this an unknown scoter. I don’t have good skeletal reference material for white-winged scoter, which would be another candidate. We don’t see evidence of a white speculum in Bird C, but these wings are extremely weathered and bleached overall, so I am not sure how much stock I really want to place in that. I think unknown scoter might be pretty good for an i.d. What say you, esteemed dead bird colleagues? As always, your thoughts or directions to additional reference material are always most welcome.





DBQ answers, saving every 30 seconds version

6 11 2015

OK, after mourning the loss of all the work of yesterday’s post, I am now ready to try and recreate it. Bird A was universally identified as a black scoter, and I’m not surprised. Given that we have both feet and wings, our odds of getting to species are fairly high. But how did everyone arrive at that conclusion? I find the feet to be the most eye-catching aspect here.

Dabbling duck foot (left) vs. diving/seaduck foot.

Dabbling duck foot (left) vs. diving/seaduck foot.

These are webbed, waterfowl type feet, but the toes are thick and fleshy, with a prominent lobe to the hind toe. These are no dabbling feet; these are the feet of a hardy, seafaring sort of duck. Within seaducks of this general size, we are looking at eider or scoter. The overall coloration of the bird is dark, so we can rule out common eider. Though males do have quite a lot of dark on them, they would also show some white, particularly on the upper surface of the wing near where the shoulder would once have been. Similarly, if this were a white-winged scoter, we would see white here too, this time in the form of the eponymous speculum. But we have a pair of wings dark throughout, and dark on both upper and lower surfaces. So we have surf scoter and black scoter remaining. In terms of the foot, if you take a look at this fantastic shot from Arkive.org, you’ll see a pretty good color match between a confirmed black scoter and our Bird A. Surf scoters, on the other hand, seem always to have some degree of reddish cast to the toes, even in the youngest birds and in females. See this charming illustration from long ago:

Surf scoters. Note even the female (left) has reddish toes.

Surf scoters. Note even the female (left) has reddish toes.

Here’s one final thing: in all our references, indeed even in the Field Guide I researched and wrote myself, one of the defining, nay, the defining characteristic that permits differentiation of a SUSC wing from a BLSC wing is the relative length of the outer two primaries. That conventional wisdom is that in BLSC, the outermost primary is shorter than its neighbors. In a SUSC, the outermost primary is equal to, or longer than its neighbor. This can be subtle, and is most helpful in a wing where the primaries have been fully extended. It’s hard to tell where the outermost primary actually ends in Bird A, even in this zoomed in image.

Closeup--is that a short primary I'm seeing there?

Closeup–is that a short primary I’m seeing there?

When we refer to a major authority on the subject, Carney’s guide to waterfowl based on wing plumage, we see an artist’s rendition that looks much clearer, not surprisingly, than field conditions often are.

Reference: http://digitalmedia.fws.gov/cdm/ref/collection/document/id/1407

Reference: http://digitalmedia.fws.gov/cdm/ref/collection/document/id/1407

It may be the power of suggestion, but the more I look at Bird A’s wing, the more convinced I am that I am seeing a skinny little outermost primary overlain on a broader, longer, next-door-neighbor primary. So, I find myself on board the Black Scoter train with all of you.

Now, on to Birds B and C, but at the moment, I am out of time, and if I break this into a two part cliff hanger, I will have something to write about next week. I’ve been at this blogging game a while now, folks, and I’ve learnt a few tricks. See you next time for the further installment of DBQ answers.





I divulge the secrets of quality control

20 10 2015

Many thanks to Dennis Minsky who wrote me with questions about the process by which a bird identified as one species by the volunteer mysteriously changes to a different species in the database. Dennis even suggested it might be a worthy blog post, and I concur. So here it is, the secret sauce.

When you folks submit a walk report, dead birds or no, I look it over. The only things I really look at in terms of the environmental data you report is to see if the time seems correct (did you really walk at 3am, or did you just slip when entering am/pm?) and check if there are any notes you left me about your walk.

If you do find a dead bird, the process of verifying your data is necessarily more involved. We are proud of the fact that we can present our data with assurances as to the accuracy of the species reported, because, as you know, we require you all to take photos of every bird you find. Many of you are experienced birders, so I appreciate very much that even the most knowledgable among you still take the time to snap those pics. Because of that, we can say confidently that every beached bird is reviewed by a second level referee beyond the person who found the bird. That referee is, and has been since 2008 or so, me. If you submit a beached bird report, and you don’t include photos, your report will still be verified, but your beached bird i.d. will be changed to “Other, Unknown” and in the notes box at the bottom of the screen, you will see this:

 

Screen Shot 2015-10-20 at 3.03.12 PMI am not always confident in my i.d., especially with the carcasses in really rough shape. Anyone who reads this blog knows that, since my uncertainties are usually paraded in front of you as Dead Bird Quizzes. But not every beached bird photo makes it to a DBQ.

In many cases, you submit your beached bird report and photos, and then you check again in a day, a week, or, more likely, a few months, and that report has been checked off as verified, your bird i.d. confirmed. In some cases, you may go into an old report and find that your i.d. has been changed and no one told you. When that happens, it’s because I have gone in and reviewed the report, any measurements, and the photos, and come to a different conclusion than you did. I realize this is a somewhat opaque process since there is nothing to alert you that this has happened.

At the prompting of Dennis’ email, I have been thinking of how better to communicate with you about these cases. These revisions come frequently enough that individual emails are not possible, but what I can do is to use that “Notes about carcass” field to let you know how I came to a different conclusion than you did. Sometimes it will be a particular field mark or coloration pattern, sometimes a skeletal clue, sometimes it’s the measurements. I can appreciate that it will help you be a better birder of dead birds if I provide some explanation of that thought process. I will start giving that a try on my next round of verifications, which is already overdue. The beached bird reports wait for no man, nor for any college professor in the throes of mid-semester stress. My gratitude for your patience, Seanetters!





DBQ answers

7 10 2015

It’s fitting that both these DBQ birds come from the Carolinas; our volunteers and friends in both states have been much on my mind given the horrendous flooding in that region, and I know some of our walkers live and work right in the heart of the most heavily impacted areas. I hope everyone in the SEANET clan is safe and sound, and if it’s not TOO much to hope, that your houses remain high and dry. You’re in our thoughts all the time, southern friends.

For these southern birds, on the other hand, there is not consensus as to the i.d. of the second bird. The first, however, was obvious to all as a Laughing Gull. The giveaways: the dark, downcurved bill, and the black legs. These are typical of winter plumage LAGU like the ones seen in this photo:

"Leucophaeus atricilla P5190038ra" by Migdoniodiaz - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons -

“Leucophaeus atricilla P5190038ra” by Migdoniodiaz – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons –

I suppose it may seem strange that I chose this bird, since everyone seemed certain of its identity. Maybe it was just me, but the gray on the upperwings of this bird seemed really pale, no? What did you all make of that? Just a trick of the light? A really pale individual? Have you seen them this light before? I ask my southern contingent especially since, while we do have LAGU up here in the great white north, I don’t see them all that often in winter in plumage like this.

How about Bird B? This one drew a verdict of Black Skimmer from John Stanton, and whenever someone suggest Black Skimmer, I always think, “Oh! Right! Could be a skimmer! I always forget about them. Northern bias shows again since that’s a species I really don’t ever see. Out of sight, out of mind, therefore. But Black Skimmer needs to be on the list whenever we have a dark wing with white feathertips especially through the secondaries. I actually thought Bird B might be another Laughing Gull, so, I dutifully went to my Beached Bird guide and, using its wing key, I arrived at a page showing immature LAGU and immature Black Skimmer side by side. Sure enough, both have white tipped secondaries, though the skimmer’s are much more extensive, with a very wide white band, while the LAGU has much more limited white. The main difference the guide mentions is actually the color of the underwing, which is pale or mottled in LAGU and dark in the skimmer. I did not provide that image in the original post, so here is the underside of Bird B’s wings:

Photo by G. Grant

Photo by G. Grant

This is actually sort of not helpful, since much of the underwing has been eaten away, most likely by notorious ghost crabs. So it’s impossible to tell whether the feathers that used to be on the underwing close to the body were mottled or clear white, so I turned again to the upperside of the wing. There, I can see what looks to me like a few rusty feathers among gray feathers. Since Black Skimmer juveniles are more black and white on the upperwing, that rusty/gray contrast jumped out at me. I am fairly persuaded, then, that Bird B too is a LAGU. Two LAGU in one DBQ? Unprecedented. Daring. Accurate? I hope. But I await verbal combat from those who may disagree.