(Speaking of the Macabre)

November 10th, 2011 | Meera

This is a preserved specimen that caught my eye after I had finished working on my birds today. On my way out, I walked through the Field’s new permanent exhibition about the museum’s role in advancing conservation science: Restoring Earth.

What’s in the jar is a Blanchard’s cricket frog (Acris crepitans blanchardi).

Cricket frogs get their name from their clear, metallic, insect-like mating call. I’ve also heard it described as the sound of two pebbles being struck together. They’re a type of tree frog, a group whose arboreal lifestyle means its members are usually rather tiny and possess unusual modifications that allow them to cling to leaves and branches. (Like adhesive toe-pads whose stickiness is built around the dynamic duo of nanoscale pillar-structures and mucus!)

Blanchard’s cricket frogs used to be an incredibly common sight in the upper Midwest, but beginning about thirty years ago, people noticed their numbers going into a steep decline. It’s still not absolutely clear why this is so, but one of the best current guesses is that exposure to large amounts of agricultural pesticides may have caused a host of physiological and behavioral changes in the frogs that interfered with their ability to properly reproduce.

I’m posting this because I was struck, especially after what I talked about last time, by how powerfully I was drawn to this particular object in the exhibit. What was alluring was precisely its eerie appearance: drained, almost milk-white, and hanging like a ghost in its jar.

Blanchard’s cricket frogs are beautiful creatures, as a quick image search revealed—I have never seen one myself, at least not knowingly.

And yet I do not think I would necessarily have walked over to and read the text beside a colorful photograph showing one of these little guys in life. This is not at all to my credit—it just happens to be true.

Now, I wonder if the exhibit designers simply wanted to showcase a specimen as it was preserved in the museum, or if, in addition, at some level they knew this about me. (And also, perhaps, about you.)


P.S. This is a good time to point you towards John Bates’s blog. John is one of the curators of the Bird Division at the Field, and he’s not only a lovely and incredibly smart ornithologist, he’s also really invested in educating people about what his team does. He posts frequently (at least by my standards!) and is reliably fascinating. His latest post, about why it’s useful to preserve pre-fledgling age specimens, might be of especial interest.

On The Uses of the Macabre

October 31st, 2011 | Meera

Happy Halloween! Today seemed like an excellent day to make this post.

Entering the bird lab this past Thursday morning, I found Mary, who usually works at the sink, sitting on a stool beside the large metal prep table that dominates the room. In front of her were two plastic trays; on each, several tidy rows of specimens were arranged. The birds that made up this small collection represented three different species: Dark-eyed Juncos (Junco hyemalis), Nashville Warblers (Vermivora ruficapilla), and White-throated Sparrows (Zonotrichia albicollis).

All three are extremely common birds in the Chicago area at this time of year, either because they’re migrating through on their way to warmer southern climes, or because they spend the winter here.

And all three are known to me personally from morning walks through the Wooded Island in Jackson Park, the treed and windy urban oasis by the lakefront where I saw the distempered raccoon earlier this spring. I love the sight of dozens of dark gray Juncos against patches of snow on the ground, like a fireplace’s worth of cinders someone has rolled up into cozy little balls. Nashville warblers make jaunty little tail flicks as they forage through low trees and shrubs (often that’s all I see of them, an olive whisk-whisk-whisk before they rustle away through the leaves). And the mustard-yellow smudges next to each eye on White-throated Sparrows always make me imagine these fluffy, familiar creatures having just feasted messily on a stash of abandoned hot dogs.

The fact that Mary was working on these birds wouldn’t, in and of itself, have been of much note except that the specimens were in a form that I’d never seen before in the lab. Normally, these are species that Dave chooses to preserve as skeletons. One of the advantages of doing so is that there are many measurements it’s possible to take from a skeleton that it’s impossible to take from a study skin. To prepare a specimen for being skeletonized by the dermestid beetles, volunteers must first remove all its feathers and skin, a process called “roughing out.”

But the specimens Mary was working with seemed to have gone only part-way through this process. On the Nashville Warblers and the White-throated Sparrows, the feathers from their bodies had been removed, but those on their heads had been left in place. And on the Juncos, tail feathers remained as well.

White-throated Sparrows

In this state the specimens appeared, I confess, both fascinating and a little macabre. The juxtaposition of intact, feathered crowns, their plumage still beautifully soft and many-colored, with the dark red muscle of de-feathered bodies, created an incongruity—the likeness of life next to the unmistakable sign of death—that forced me to stop.

Why had some feathers been left on these birds?

Mary soon explained that in each of these species, subtle but significant differences in plumage coloration can be observed. Such variations raise a host of scientific questions (Are the disparities related to sex, age, or region? Can they be traced to genetic differences? Is one form of coloration more common than another, and if so, why? Does the prevalence of each pattern change over time?).

To document these variations, Mary was collecting caps from all three species, as well as tail feathers from the Juncos—because these were the parts of the birds’ bodies where the differences occurred. This way, the caps and tail feathers could become part of the museum’s collections and potentially help to answer some of these questions.

But when she was finished collecting what she needed, the beetles would go on to skeletonize the rest of the specimens’ bodies as usual, thus preserving the ability to take bone measurements from them in the future. The fact that I’d seen the birds’ bodies in this state was a coincidence: an accidental glimpse at a bit of scientific frugality.

Here are some of the variations this kind of data will hopefully help to quantify:

Junco caps and tail feathers

Juncos can have crowns that vary from a light gray to a deep black, sometimes tinged with brown—and while all Juncos have white outer tail feathers and black inner tail feathers, there can be considerable variance in the amount of white and black on the intermediary feathers. This photo doesn’t show the subtle differences in the shades of the crowns very well, but you can clearly see how much more black than white there is in the tail feathers of the bird in the foreground, and how much further out the black extends to the edges of its tail.

Nashville Warbler caps

Nashville Warblers can have a patch of wonderfully rich chestnut-colored feathers in the center of their crowns, something I’ve never noticed when birding because the tiny flecks of red are all but impossible to see amidst or underneath their otherwise gray head feathers. Adult males all have some red in their caps, but the amount can vary widely; and some adult females have a little ruddiness there, too, while others have none. These differences are unfortunately very hard to see in the photo I took, but if you squint you might be able to see some red stippling in the third specimen from the left.

White-throated Sparrow caps

Finally, White-throated Sparrows actually have two well-documented morphs, or variant forms. You can see these quite clearly in the photo above: one morph has distinct black and white stripes running vertically down its crown, while the other has black and tan stripes arranged in the same pattern. Both morphs can be found in both sexes.

DNA analysis has shown that this polymorphism in White-throated Sparrows arises from genetic differences. Both White Stripe and Tan Stripe birds, as they are usually called, show a slight preference for mating with individuals from the other morph. This opposites-attract tendency (which goes by the unwieldy name of “disassortative mating”) keeps the approximate proportion of each morph in the overall population stable, so that neither morph disappears or becomes dominant.

Most fascinating of all, at least in the case of White-throated Sparrows, the morphological variations we see in their crowns are also associated with clear behavioral differences. White Stripe males are more aggressive and more showy—they’re more likely to engage in “spiraling,” a wonderful-sounding behavior that involves singing as they ascend the branches of a tree by circling it. They’re also less dedicated providers of parental care, and less monogamous than Tan Stripe males. As for White Stripe females, they are almost as bold and selfish as their male counterparts. (This may explain why both WS males and females seek out calmer, more reliable partners from the opposite morph.) For more on this subject, I’ll point you to this excellent post by GrrlScientist, who explains the genetics behind these behavioral variations far better than I could.

What I love about my own experience of all this is that it illustrates so clearly a principle I’ve always felt to be true about the study of natural history. That is, the macabre (like beauty) is not a thing that exists as an inherent property of the world, not something with a palpable presence in time and space. Instead it arises out of the complex interaction between ourselves and the world. Even if disquiet is our first reaction to a memento mori, it need not be our last.

But to the extent that encounters with the macabre invite curiosity—like the curiosity that struck me so forcibly when I walked into the lab and saw those unusual-looking specimens on Mary’s trays, and led me to learn some of the things I’ve shared with you today—I think it’s an extraordinarily useful quality in science.


I would be remiss if I didn’t tell you about two additional things I hope you will investigate:

1) Flinchy, the t-shirt company co-founded by my favorite fellow bird lab volunteer, Diana Sudyka, has several new designs available for purchase. I own one of them, and can testify to its quality and attractiveness. And greater luminaries than me endorse Flinchy shirts, too.

2) I wrote a piece for the Scientific American Guest Blog this week about my rather extraordinary friend Nina and her Field Museum project, LinEpig. You can find it here, under the curiosity-provoking (though not macabre) title “Internet Porn Fills Gap in Spider Taxonomy.” Nina picked the title, because she knows even better than I do that first you catch the eye, and then you tell the story.

Nina at work

Till next time, dear readers-mine. I hope it won’t be so long again.

The 100th Species

September 22nd, 2011 | Meera

Since I started volunteering in the Bird Division of the Field Museum a little over two and a half years ago, many things have changed.

I’ve gotten much more confident and relaxed about preparing specimens than I was in my first tentative months, though I feel no less amazed by the process each time I sit down to begin.

The plastic ID card I use to beep myself in and out of the museum and to access the staff-only elevators (something which still gives me a thrill) has gotten scratched and worn.

I’ve made some wonderful friends.

And, as of today, I’ve worked on one hundred different bird species.

You can find the list in its entirety here, where it will continue to grow as Dave keeps putting out new species for me to work on. But I thought I’d give the 100th a bit of fanfare in this post, especially since it’s not a bird that tends to get a lot of fanfare.

The 100th species on my list is neither unusually large nor remarkably small, neither brightly colored nor glossy and dark. There’s nothing exotic about it. It’s just another little brown bird. Yet if there’s one thing I’ve learned over the past few years, it’s that the more data we have about a particular thing, the more meaningful that data is and the more useful it is to science.

Paradoxically, the fact that White-crowned Sparrows are extremely common in our collections—according to a search I just did of the Bird Division’s database, at least 1433 individual Zonotrichia leucophrys specimens already exist in the museum, dating back to 1863—makes every additional study skin we prepare of even greater value. With a healthy-sized data-set like that, any researcher wanting to do a genetic study, track migration patterns or wing-lengths over time, generate a set of characteristics that birders or bird banders can use to age or sex a bird in the field, or answer any of a thousand-and-one impossible-to-predict future questions, will have a larger body of information to work with and a far better chance of producing reliable results.

So here it is: One big milestone for me, one precious incremental addition to scientific data, and one beautiful bird.

White-crowned Sparrow

White-crowned Sparrow

100th species

P.S. You may have noticed that this little fellow, despite being called a White-crowned Sparrow, has no white visible on its crown. That’s because it was an immature bird, probably hatched earlier this year, and had not had a chance to moult into its adult plumage before it died. Females of the species also don’t live up to their name, and look similar to juveniles—but their tails aren’t quite so long as you see here, and they don’t have any white bars on their wings. Aren’t bird names wonderfully confusing?