Thursday, August 28, 2008

Quick Stop, Deep Impressions

Today I serendipitously found myself driving in the general area of Montezuma National Wildlife Refuge with a little extra time before I had to pick up Reina nearby. That translated into 20 minutes of actual birding time, giving me a brief glimpse at the newly-constructed shorebird habitat surrounding the visitor's center.

New shorebird habitat created at Montezuma populated by
waterfowl, shorebirds, gulls and terns. I'd make this a quiz
but I don't even know everything that's in this image!

Twenty minutes is short-changing what it deserves but you take what you can get, and I took it all. Immediately after turning into the refuge I scored a trifecta of swallows. I often see that word used as a high-falootin' way to say "three," but this was more than that. My thoughts on the drive up, when they wandered from possible shorebirds, returned to the fact I haven't seen a Bank Swallow this year.

I expected to find Tree Swallows, thought I'd pick up a few (or more) Northern Rough-winged Swallows, and I hoped for a Bank. The first birds I found were swallows, dozens of them, swarming over a vegetation-covered mudflat. Tree Swallows were easy to pick out, even before getting out of the car. Once I opened the door Northern Rough-wings were clearly audible, and I eventually scoped a single Bank Swallow on a snag among more rough-wings. One, two, three, in that order; a trifecta. Wish I'd put some money down.

Young Semipalmated Plover boldly exploring the mudflats.

Shorebird numbers and diversity weren't phenomenal but not disappointing. Least, Semipalmated, Pectoral, Solitary, both Greater and Lesser Yellowlegs, and Killdeer pocked the mudflat. Caspian Terns and Ring-billed Gulls mixed in among the Canada Geese and a few other species of waterfowl, including Blue- and Green-winged Teal, Northern Shoveler and the resident Mallards and American Black Ducks.

There were two highlights on this trip, the first being five Hudsonian Godwits that stuck around almost long enough for a clear photo. Hudsonian Godwits are essentially unheard of in the spring and possible in the fall, but you never plan on finding one in our region. Better and more active birders than me have chased and missed them on many occasions. This was a pretty awesome highlight! I was setting the camera when I heard them take flight so I quickly pointed-and-shot, I'm ecstatic they're even in the frame!

From Birds
Hudsonian Godwits flying south, identified by the
dark underwing coverts and white stripe on the upperwing.
I also heard them calling until they were out of earshot.

Fair warning: that's the end of the birds for this post, but you're welcome to read on to discover the other highlight as I mount my soapbox.

I must confess, each election cycle I become more of a political junkie and this week I've been hitting the stuff more than ever. Not only have I watched more speeches from the Democratic National Convention than I intended to, I've also followed some blog discussions and even watched some of the pundits blab on. Normally I can't stand the partisan punditry and spin, and that's just the talking heads -- forget about campaign mouthpieces. And this year with the Hillary-Barack drama, forget about it. But I'm tolerating it this time around as it's been a momentous week for our country.

The fact the Democrats nominated someone who looks different than those guys on our dollar bills (to paraphrase Sen. Obama) is a monumental occasion. The fact they came within a pantsuit of nominating someone of a different gender from the dollar bill guys doesn't just double the magnitude, it amplifies it immeasurably. I found myself pretty emotional listening to many of the speeches and watching the interviews with the delegates, both Obama's and Sen. Clinton's ardant supporters, participants from the Civil Rights Movement, and the everyday folks who have been affected, directly or indirectly, by the long struggle for voting rights.

I often drive through Seneca Falls, NY after visiting Montezuma, but this time it was with a feeling of excitement and reverence as I passed by the Women's Rights National Historic Park, the first time I've felt that way as I drove through town. The significance of this site, not just for women's suffrage but for everyone, was more omnipresent today than ever before, especially this month (88th anniversary of the 19th Amendment), especially today (45 anniversary of Martin Luther King's "I Have a Dream" speech), especially right now after listening to Sen. Obama's acceptance speech. We, as a country, have come a long way, baby!

Updated to add: Boy, and now with Alaska Governor Sarah Palin on the Republican ticket, what an election this is! I can't begin to imagine what else will happen in the next 67 days.

Soapbox dismounted.


Wednesday, August 27, 2008

Flight Call Identification: Veery

This is the first in a series of posts presenting flight calls of nocturnal migrant birds. If you haven't yet, you might want to refer to my introduction to flight calls before, or after, reading this account.

The Veery (Catharus fuscescens) spends its summer in damp, deciduous forests, stretching in a loose band across North America. The song is familiar, often used as an example of the dual syrinx, its downward-spiraling flute-like notes a marvel of nature. Because winters are spent in central and southern Brazil their migration should cover the eastern two-thirds of the U.S., though eBird shows show reports are spotty across the Great Plains. Perhaps this is more likely a testament to the number of observers and the number of Veeries seen during migration. Flight call monitoring might provide a more accurate assessment of where the birds are migrating.

Veery reports according to eBird (map created 28 Aug 2008).
How many of the blank areas are simply "fly over" regions?

Edited to clarify the map: The above map displays all reports throughout the year, both on the breeding areas and on migration. For example, the light green wash (indicating relatively fewer sightings) across the gulf-coast states are migratory observations, the dark green wash across the southern provinces and northern U.S. are sightings from the breeding ground. Dark green indicates high frequency of reports, likely due to repeated observations on breeding territories. Light green, or areas of infrequent observations, are due to the passing nature of the Veery in these areas.

For life history information about the Veery, including listening and viewing the song, visit the All About Birds web site.

Timing-wise the best time to listen in the northern U.S. is now. According the the Birds of North America Online peak migration in New York runs from late August to early September, in Minnesota 31 August is an average peak date. Southern birders have a couple weeks: in Louisiana migration peaks between 15 - 30 September.

Like the other Catharus thrushes, Veery flight calls are relatively low in frequency (pitch) and are relatively long. The call I'm highlighting here, freely available online through the Macaulay Library online archives, is about a quarter-second long (250 milliseconds). I find the thrushes a bit easier to hone in on than the even-quicker warbler and sparrow flight calls.

The Y-axis shows frequency in kiloHertz (kHz), which you can think of this way: the higher the kHz, the higher the pitch of the sound. Johnny Cash sang at low frequencies, Tiny Tim at high frequencies. Annoyingly high frequencies.

Looking at this call we see the Veery's flight call is relatively linear, typically keeping within 2.5 - 2.0 kHz. The frequency usually declines during the length of the call, which is why the pitch falls when you hear it though the heavily-modulated ending may slightly rise. This call shows up very dark and bold, indicating it's pretty loud. The bird must have been close to the microphone when recorded.

Veery flight-call, full speed.

Pretty fast, right? It's intimidating to think this is one of the longer flight calls. Examining the spectrogram shows this call starts pure, the note is slightly-descending but the line is flat, not wavering (modulated). The end of the call is heavily modulated, though, rising and falling very quickly, which gives a distinct "burry" sound.

Listen to the same call at quarter speed, it's easier to hear those characteristics: descending in pitch but unwavering, then fluttering rapidly through the modulated end of the call.

Veery flight-call, quarter speed. Listen to the
descent in pitch, then the fluttery, modulated ending.

Try listening to the quarter-speed version a few times, and once you clearly hear the characteristics try listening to the following clip, the same call at half speed. Can you still hear the characteristics?

Veery flight-call, half speed.

Again, listen to the half-speed version a few times, and once you're comfortably hearing the characteristics at this speed, scroll back up and listen to the full-speed version.

Of course, this is one call of a single individual, and I've mentioned you're bound to encounter variation. That's especially true in Veeries. Oftentimes the Veery's entire call is modulated, though the heaviest modulation tends to be towards the end of the call, like this one. This call could be confused with the other thrushes (Hermit, Wood, Swainson's, Gray-cheeked, Bicknell's; even bluebirds and robins) as well as other species that give thrush-like calls, meaning relatively long and in the lower frequencies. These include tanagers, meadowlarks, and orioles.

For more Veery recordings and spectrograms visit Call Notes & Flight Calls.

  • Veery flight call recorded by Bill Evans, 24 April 1990 in Alabama, U.S.
  • Recording courtesy of Macaulay Library, Cornell Lab of Ornithology.
  • Spectrogram created in Raven Pro, Bioacoustics Research Program, Cornell Lab of Ornithology.
  • For more information about the Veery visit All About Birds.

Tuesday, August 26, 2008

Listening for Flight Calls

In a recent post I highlighted that nocturnal river of birds that flows overhead through the migration months, specifically mentioning we had a big push of Veery through the Finger Lakes region (NY) that week. I realized I hinted around, but never directly said, "Go out and listen!" Let me say it here: on a good night it is truly mind-numbing to realize how many birds are flying over your head in the cover of darkness if not the sheer diversity. As one birder put it, you're likely to hear more Gray-cheeked Thrushes during a couple of hours on a good night of migration than you will ever see in your lifetime.

I also realized some might want to listen for flight calls in their area and try to identify what they're hearing, but wouldn't know what to listen for. Far be it from me to point out something cool but not provide the tools to enjoy it, so I plan to post brief tutorials about some of the nocturnal migrants that you may hear winging their way south. I'll try to time each species profile with their chief migration windows, but as migration peaks will differ with latitude that won't always be possible. You can't please everyone, but there it is.

Updated to add: Jump ahead and learn about Veery calls, or continue reading below to learn about flight calls in general.

So, about flight calls. They're different than the songs used for advertising for a mate or declaring a territory, they're different than the contact notes you'll hear between a mated pair or between parents and offspring, different than the alarm calls. Their function isn't truly known, though current thinking is that flight calls maintain groups and also stimulate "migratory restlessness" (zugunruhe, the "urge to migrate"). If you are interested in a more detailed overview about flight calls I recommend that you read this article.

Flight calls are short. Really, really short. The longest are about a half second long, or 500 milliseconds, and the shortest clock in at about 30 milliseconds. The first time you listen for them it's tough to even hear them, but with some time to acclimate your ears and with some focused listening they'll start to pop out from the ambient noise.

Not only will you hear them, but with enough time, practice, and patience you can hear the characteristics of each call. The calls may be high- or low-frequency (high or low pitch), they can rise or descend in pitch, or they can do both in the same call. They can be heavily modulated, meaning the note wavers and sounds "burry," or be a pure, sweet sounding note. Above all, though, they're short.

Because of their brevity I find the most useful way to learn a call is to study its spectrogram. This has the advantage of seeing the characteristics, a bit easier to process - much like learning what the bird looks like tends to be easier than learning the songs. I then play the recording, but slow it down so I can listen to it at one-quarter of the actual speed. This gives more time to get a handle on the sound, really hearing each characteristic. I then listen at half speed a few times, then finally at full speed. At that point I'm hopefully still hearing the characteristics.

Each species has a unique call, so flight calls can be a useful way to identify nocturnal migrants. Be warned that the experts are the first to admit that not every call can be identified to species, especially by ear. Even with sophisticated analytical software taking dozens of measurements on the spectrograms we often leave calls categorized as a suite of possible species. For example, the Flight Call Library on Bill Evans's OldBird web site includes examples of character groups: calls of various species that are so similar they are near impossible to separate.

There is variation in the calls. It's amazing to me a half second provides enough time to introduce variation, but it happens. Be prepared to let some calls go, lumping them into a loose category ("That sounded like a double-up," or "that was one of the zeep complex") but hopefully many calls will become recognizable.

And even if you don't identify any calls, it's simply a marvel of nature to hear the numbers and the diversity that you may have never realized pass you by each spring and fall.

Finally, a disclaimer: I'm not an expert in flight call identification. Much of what I've done with them relates to collecting flight calls, meaning I've deployed autonomous recording units and then run detection software to pull out the flight calls. I've spent hours browsing those detections to separate the calls from the "false-positives" (or, more accurately from where I sit, the "junk"). In researching and writing this series of posts I'm hoping not only to educate anyone not familiar with flight calls, but I'm also anticipating the process will allow me to dig deeper into the subtleties of each species' call. Naturally, I hope you will jump in and join a dialogue about what I present here and especially what you're noticing at your location.


Monday, August 25, 2008

New Bird ID Quiz

Well, it's not really new, it's been going on for much of the summer by the folks over at eBird. Instead, it's a new type of quiz: rather than seeing the bird and figuring out (or guessing) what it is, they're providing a range map based on actual eBird data. We have to figure out the species.

This is important to know when viewing the maps: they present all data from all months from 2003- 2008. So, you're seeing all accepted sightings of breeding, wintering, dispersing, migrating, and wandering birds.

Last week's quiz, the first taking into account all of the Americas.
Have a guess, then find out if you were right on the eBird site.
Click on the image for a larger version.

I find the process fun (the product of a warped mind, I suppose), and very paradoxical: it's not as easy as it sounds, but it's not as hard, either. I doubt many people will think it's easy, unless your name also happens to be on the cover of a field guide and you've spent years of your life assembling data to produce similar maps.

But taking some time to digest what you're seeing, such as concentrations of sightings, areas of infrequent sightings, locations completely lacking the species, or a scatter-shot of non-contiguous sightings, you can start to eliminate obvious groups of birds and, if persistent, whittle it down the right species.

This week's quiz. The answer should be up on eBird soon,
but try and figure it out based on what you see.
Click on the image for a larger version.

Feel free to leave guesses and/or answers in the comments, along with your reasoning. AT the moment I have no idea what it is, but I'm hoping a bit of thinking later this evening will help me narrow it down. Good luck!


Friday, August 22, 2008

Cascading River of Birds

If you've paid attention to bird reports recently you already know migration is well underway, and has been, conservatively, for about six weeks. Was it Pete Dunne who once pointed out that if summer were bookended by bird migration it would only be a few days long? Whomever it was went on to point out the last migrant passerine was spotted winging its way north a couple of days before the summer solstice, and a couple of days after the solstice the first yellowlegs was on its way south.

Here in the Finger Lakes region of New York shorebird reports have been steady from Cayuga Lake and Montezuma NWR, and we've already had a Solitary Sandpiper show up at our backyard pond in the southern tier. In fact, it was a year bird and the first we've recorded on fall migration. More my speed these days, though, are the sound waves emanating from the river of birds that will be flowing over our heads for the next couple of months.*

If you've never been you should head over to Bill Evans's "" website. Bill's sole intention is to learn about nocturnal bird migration and share the knowledge with anyone who cares to listen. He focuses on flight-calls, those short, simple "tseeps" and chips (among other impossibly short notes) you may hear overhead. Not only does he teach you how to identify the sounds with Flight Calls of Migratory Birds, a CD-ROM developed with Michael O'Brien, but he also provides instructions on how to build your own microphone set up using materials from local garden and grocery stores (after a trip to Radio Shack, naturally). And that's not all, he also provides analysis software free so you can use your computer to view, study, and listen to what flew over your house while you slumbered. No more dark circles as you stumble into work the next morning!

As I mentioned in an earlier post, I also study nocturnal migration, though we use autonomous recording units developed at the Lab. Bill's web site and his CD-ROM have been instrumental for me, learning to identify those less-than-500-millisecond long calls; it's opened a new avenue of birding. In fact, I'm building my own "flower pot" microphone so I can record migration over our house. What a mesh, for me, of "work" and "play," and now that the floodgates are open on this fall's migration I'm excited to listen for what's passing by. Recently we've been hearing more and more activity in what Sinatra called the wee small hours: three nights ago it was a huge push of Veerys with a smaller flight the next night.

More to come on nocturnal migration as the season progresses, and happy fall to everyone!

*Dates may vary with latitude, offer available across North America. Act now, don't miss out!

Tuesday, August 19, 2008

If You See Her, Say Hello

Recently I received a letter marked "Official Business" from the federal government which, in my usual style, especially in this ramped-up election cycle, was set aside for another time. Well, it turns out to be good news for a change. When I finally did open it I discovered I had been awarded a bona fide "Certificate of Appreciation" from the U.S. Geological Survey and the Canadian Wildlife Service. That's right, my efforts have been internationally recognized!

It all started about three months ago on our trip to Chincoteague, VA. It was late May, good timing for shorebird migration, so we stopped in a few places on Delaware Bay to look for Red Knots and/or Horseshoe Crabs among other mid-Atlantic goodies. At one of those stops we found a beach littered with Sanderlings and a smattering of Dunlin. Several came within a few yards of us as the Sanderlings alternated chasing the surf and being chased by the surf. That's when we noticed one bird was tagged.

Tagged SanderlingTypical Sanderling behavior: constant motion, running with the
waves. Click on the image for a larger view and you can read the tag.

It also turned out this Sanderling was missing a leg. How that happened we'll likely never know, but by recording the band style, color, and markings we were able to find out what happened to its remaining leg: who affixed the tag, where and when was it done?

tagged SanderlingNicely posed, allowing plenty of time to
record the tag and sighting details.

Turns out this handsome fellow, or pretty lady, was banded May 19th, 2006 in Goshen, New Jersey. At banding it wasn't possible to determine with any precision how old the bird is, the official record shows it was "hatched in 2004 or earlier." Sex is "unknown," and as far as they listed, the only encounter data was when we crossed paths on May 24th, 2008 at Slaughter Beach in Delaware.

Delaware Bay mapThe tagged Sanderling was resighted about 28 miles from
where it was banded two years ago. We're sure it has seen
much more travel than that over the past two years.

With Bob Dylan's "If You See Her, Say Hello" as background music my mind moves from where it was banded to where it's been, and where is it going? Knowing who put the tag there answered some questions but opened many more. What has this bird been doing for the past two years? Where does it call home, that beach where it spends the winter? Did we both just arrive at Slaughter Beach that day, both to depart shortly thereafter? It's possible this bird winters along the mid-Atlantic coast, but consider this: the Sanderling's wintering range extends from southern Maine south to southern Argentina, or, said another way, it "spans some 100° latitude, encompassing most temperate and tropical beaches in the Americas" (from the Birds of North America Online). This bird might be loafing on this beach, the same beach it spends each winter, or it might have flown up to 6,500 miles just to reach Delaware Bay.

Sanderling DistributionDistribution of the Sanderling, courtesy All About Birds.

Where has it summered? Sanderlings breed in the high Arctic, and I assume this one, one-legged and all, still reacts to the overwhelming urge to migrate and to breed. Its short breeding season is probably spent some 2,500 miles from our Delaware rendezvous, high in Nunavut, Canada.

Finally, how does it move between those two sites? Does it take the same path year after year, stopping in the same locations? In a sense, we do the same thing. We travel the same route to coastal Virginia each summer, following the same network of interstates and local roads, often stopping at the same restaurants and rest areas to recuperate. I suspect stopping in Goshen, NJ one year and Slaughter Beach, DE the next is akin to us stopping at a diner in Clark's Summit, PA one year and a different restaurant in neighboring Scranton the next.

That similarity aside my USGS-CWS achievement seems a little less noteworthy while this individual's accomplishment is awesome; awesome in the old-fashioned, Biblical sense, as well as the Jeff Spicoli surfer-sense (get me near a beach and my mind always wanders to "Fast Times").

So, with due deference, I yield my certificate to this Sanderling. By the time I'm writing this it's already finished this year's breeding attempt and is winging its way south to whichever beach, temperate or tropical, it calls home. I wishing it safe travels, hopefully we can cross paths next spring again. Oh, and if you see her, please say hello - and report your sighting!

Sunday, August 17, 2008

The Chrysalis Crack'd: Birth of a Butterfly

Unfortunately I did not capture our Spicebush Swallowtail's actual emergence on film. In fact, we didn't even see it. Reina and I were sitting at the kitchen counter sharing a version of Elvis's favorite (peanut butter and banana on toast, drizzled with honey) when I looked out at the caterpillar jar on the porch.

"Sheesh, that black label on the towel that the jar is sitting on always makes me thing something happened in there. This time it's actually moving."

Wait for it.

Reina looked. "It is moving!" We ran outside to see. The chrysalis had cracked open.

The cracked chrysalis, already turning brownish-
yellow a few hours after the butterfly emerged.

We watched the wings expanding as fluid poured into the veins.

Above the chrysalis there was a newly-emerged butterfly, still climbing to a higher perch to let her folded wings droop down to form.

For the most part she stayed still but she did start moving higher and higher, eventually perching on the stocking ceiling. We decided we should place her somewhere natural where she could, if she chose, start fueling up - we figured after a lifetime of eating leaves she was ready to sip nectar for the first time.

Reina reached in to let her climb on her finger, but the swallowtail had other plans. She climbed on, then kept climbing, seeming to want the highest point possible. We finally succeeded in placing her on a flower, choosing a Bee Balm. Patches of these Bee Balm are nectar hot spots, akin to the pubs in Ireland or perhaps malt shops in 1950's America. We've seen everything from butterflies and bees to hummingbirds and wasps, dozens at a time, refueling and socializing.

Not yet interested in food she rests on a well-worn Bee Balm.

And as she perched, mostly still, what an awesome opportunity to photograph her.

Proboscis still coiled, not yet probing for nectar, the veins on
the wings prominently filled with fluid. That fluid will be
retracted into the body once the wings are fully spread.

I'm not sure how easily you can sex these butterflies, but they say the
blue (female) or blue-green (male) band on the hindwing indicates
the sex. If true, sex will be determined by how your monitor is set.

Eventually she climbed to the top of the flower head and slowly, for the first time, beat her wings. It must be an amazing but bizarre feeling for a once-was caterpillar to suddenly have appendages it never knew, or could even know about.

The first wing beats of Sara.

Eventually she made a short flight on to the lawn, at which point we helped her back to the Purple Coneflowers. She took another short flight and perched on the lattice underneath the Trumpet Creeper where she was a bit more secluded and left alone by the patrolling wasps and bees. A couple of hours later she flew out, then up, circled the rooftop and headed to parts unknown. Empty nest again.

Except we kept seeing her over the next few days in various parts of the yard. Apparently she'll live anywhere between two days and two weeks, hopefully mating and laying eggs . . . back on our spicebush, if we're lucky.


Friday, August 15, 2008

From Chrysalis to Butterfly

One of the greatest aspects about having a kid is you get away with things that civilized adults in polite society can't. Of course, as a naturalist you can get away with them anyway as long as you're fine, or unaware, that you're labeled "eccentric," "adolescent," or whatever. While that actually flatters me more than anything (and why I love Monty Python, the Kids in the Hall, or any other comedy troupe that regularly sends up "businessmen"), it's still reassuring to know if pinned in a corner you can tie anything you do to your kid, " . . . it's a great learning experience for a pre-schooler!" Suddenly you're the parent of the year.

So, with continued great excitement, here is a decidedly non-birdy post following up on my my earlier excitement about our spicebush. This time I, er, Reina and I collected one of the spicebush caterpillars we found to watch the caterpillar-to-butterfly transition.

Spicebush Swallowtail caterpillar, fourth instarWhen we first found the caterpillars they were in their fourth instar.
Maybe next year we'll recognize an egg and watch the full process.

We didn't collect any until they reached the fifth instar stage. Not for any environmental reason, but mostly because we waffled about whether we should take one in captivity - where would we put it? By the purest of coincidences I walked by the "give-away" table in the staff lounge at the Lab and found a couple large vases for the taking - perfect caterpillar containers!

Spicebush Swallowtail caterpillar, fifth instarUnrolling a spicebush leaf revealed a beautiful fifth-instar caterpillar.

We had become experts in finding the rolled-up spicebush leaves that contained a caterpillar, though we were never sure what instar to expect. After enough experience you can probably guess correctly by the weight of the rolled-up leaf, startling your friends and perhaps taking in a few extra dollars for beer and chocolate milk money.

Once we found a leaf that contained the caterpillar we wanted we clipped the leaf and placed it in the thoroughly cleaned vase, added a few extra leaves and a branching twig from a recently-deposed Autumn Olive, and added a breathable top (my wife graciously gave up an old stocking for my, er our, observations), and placed it on the back porch.

Captive Spicebush Swallowtail caterpillar, fifth instarCaptive caterpillar, seemingly OK with its new surroundings.

I was never able to find any information about the timing of any transitions. We had no idea how long it had been a fifth instar so we couldn't predict how long until it turned to the prepupal orange-yellow stage. Once it became prepupal, how long until it formed a chrysalis? And from then, how long until butterfly emergence? Now we had a change to discover on our own.

I did learn that some pupae (chrysalids) are green and some are yellowish-brown, and that it was thought green ones will produce a butterfly this summer while brownish ones overwintered and emerged next spring. However, one site also debunked that hypothesis as some of their green ones overwintered and some brownish ones emerged the same year. Scientific observation and experimentation at its best: it seems to make sense that a green chrysalis would stand out during the winter months but blend nicely during the summer, while a brown one would mimic a dead leaf through the fall and winter. But when tested a seemingly logical hypothesis was not supported.

So, only knowing generally what to expect (if we did things right a butterfly was at the end of this process) we removed old leaves daily and added fresh ones, we watched often, and we even added a second fifth instar caterpillar a couple of days later. One Sunday morning, three days into the process we woke to find we were missing one of the "old" ones and a "new" caterpillar was in the vase.

Captive Spicebush Swallowtail caterpillar, pre-pupalSunday morning it was greenish-yellow, by the time I took
images Sunday afternoon it had changed to the more
familiar pre-pupal orange-yellow coloring. But for how long?

Monday morning, one day after finding the prepupal larvae perched on top of a twig, we noticed it in a very awkward position, seemingly ready for chrysalis formation.

Captive Spicebush Swallowtail caterpillar, pre-pupalLeaning back on the underside of the twig, tail attached,
head suspended by a short thread. Soon a chrysalis?

Not wanting to miss the prepupal-to-pupal transition I set up the intervolemeter on my camera to shoot every minute, placed the tripod, and went off to work. When I got home nothing had changed, other than I have over a hundred images exactly like the one above. It stayed like that all day, but Tuesday morning, two days after turning prepupal and one day after "suspending" itself, we awoke to find a chrysalis.

Captive Spicebush Swallowtail chrysalis, yellowThe chrysalis suspended to the underside of the
twig by a central girdle of thread. I'm bummed we missed
the actual transformation, I'm dying to know how
it got from caterpillar to "suspended animation"!

I keep writing chrysalis and not cocoon: if you're unsure of the difference check here. Anyway, it started orange-yellow, like the prepupal larva, and slowly turned to a greenish, leaf-mimicking structure.

Captive Spicebush Swallowtail chrysalis, green
We hoped that indicated it would emerge this season, though that turns out to be dependent on a host of factors, such as temperature, photoperiod, and even information derived from the host plant. That's right, the caterpillar "knows," based on chemicals in the spicebush it was eating, on whether it's advantageous to emerge this season or wait until next spring.

If you looked carefully at the two pupa images you might notice they are actually close-ups of the two chrysalids side-by-side. I took those images after the second caterpillar pupated but hadn't yet turned color, giving a nice comparison.

Captive Spicebush Swallowtail chrysalids, comparison of green and yellowThe newer chrysalis is on the left, less than a day old.
The green one on the right is two days old.

I'm in complete awe of this process, especially one nagging question: how strong is that thread? How much can it take before it snaps?? I've been extremely careful every time we move anything, fearing it's going to slip loose. Reina, not so much: she's putting these guys through every natural bang-and-bump they'd experience in the wild.

As of today we're batting .500: one emerged 15 days after forming the chrysalis, the other is still pupating - 22 days and counting.

Spicebush Swallowtail butterfly, female(?)The adult after her first flight - I now call her female based on two
things: the bluish rather than blue-greenish scales on the upper
surface of the hindwing (to the best of what I can see and my
limited experience), and the fact Reina named her "Sara."

Any bets on that second one, will we see it this year, or perhaps next spring? Is it slower to emerge based on temperatures, photoperiod, or perhaps waiting until next year based on what the plant was telling it in the two-day difference between chrysalis formations? Perhaps something went wrong and it died during pupation.

My guess is we'll see something in the next week, it seems to becoming a lighter green along the sides and darker in the middle, perhaps indicating the black adult is there, soon to emerge. A fascinating process, whether you're four or, shall we say, "closing in on" forty.
  • Interested in knowing more about Spicebush Swallowtails? Look at this Critter Catalog for all of the details!

Tuesday, August 12, 2008

Sitting Out the Dog Days

Here we are, having reached the dog days of summer. Well, usually these are the dog days in these parts, the hottest weather usually settling in during August, but in reality we're having an amazing stretch of cool temperatures: highs this week have been in the low 70s (F).

Rather than enjoying this near-perfect weather (the threat of hail the only downside) I'm plopped on our couch, propped up by pillows and Vicodin, recovering from having a hernia repaired. Simple procedure, they assured me, it apparently went well. Now I've got some time to kick back and heal. I presumed I'd get in some reading, organize all the photos multiplying on our hard drive, write and post more to this blog, perhaps watch some Olympic competition, and even browse detections of our nocturnal flight call recordings.

Since I can't sit normally I haven't been able to work on our desktop computer, so no image organization, blog-posts-with-pix, or work browsing has been possible as yet. Maybe later this week. Instead I've spent most of my time staring out the window, legs up on the couch, watching/listening for birds and whatever insects I can see landing on our wildflowers.

Bird list is small, and expected. Eastern Towhee call notes, "to-wheeee," are the most common sounds, followed by Blue Jays "jay, jay, jay, jay" and the drawn-out "annk, annk, annk" of the Red-breasted Nuthatch. I can hear American Goldfinches potato-chipping as they fly by, and a family of Eastern Phoebes silently hunts outside my window. I suspect the same ones that nested on our house, but which brood? First, second, or both? Surprising in their absence are Song Sparrows and Common Yellowthroats.

Monarchs are the most common butterfly, though Eastern Tiger Swallowtails have made a couple of fly-bys. My daughter moved the Spicebush Swallowtail chyrsalis in from the porch so I could watch it, and to be honest, that's been more exciting than any Olympic sport yet. And it's still a chrysalis, though the anticipation is killing me. Well, it would be, if weren't for the soothing effects of Vicodin.

Speaking of which, time for my fix. I hope you're enjoying your August as much as I'm enjoying mine!

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