Thursday, October 06, 2005

The final camouflage

Lloyd Spitalnik, the Central Park birder and photographer who photographed the sequence of the Black Swallowtail caterpillar turning into a chrysalid last week, sent the photo above and wrote:

Here is what the chrysalis looks like as of today. The color has really changed and now it is nicely camouflaged.
Thought you might be interested.
See you,

PS from Marie
You might be wondering which one of us is using the right word for the caterpillar pupa,
Lloyd or I. Well, we're both right. Both forms are correct. I use the latter because it's easier to make a plural out of chrysalid than chrysalis

Wednesday, October 05, 2005

Do birds dream?

Yesterday,while writing about roosting grackles, I idly wondered whether birds dream.I imagined that nobody knew. Today, after doing some research, I've come up with an answer: yes! And what do songbirds dream about? Singing. Here is a paper casting light on the subject from the University of Chicago Medical Center:

Singing silently during sleep helps birds learn song

October 27, 2000

In a study that suggests that sleep plays a central role in the learning process, University of Chicago researchers show that sleeping songbirds replay, rehearse, and perhaps reinforce the neuronal activity patterns of song production.

Song acquisition is often used as a model system for how humans learn speech. Young birds learn to sing by listening to adults and then practice by listening to their own attempts. In the October 27 2000, issue of Science, the researchers describe how the neurons involved in song generation precisely recreate during sleep the complex activities involved in singing--though no sound is produced.

"From our data we suspect the songbird dreams of singing," said Daniel Margoliash, PhD, associate professor in the Department of Organismal Biology and Anatomy at the University of Chicago, and principal investigator in the study. "The zebra finch appears to store the neuronal firing pattern of song production during the day and reads it out at night, rehearsing the song and, perhaps, improvising variations. The match is remarkably good."

The recent miniaturization of neuronal recording gear allowed Margoliash's team to study the activity of individual brain cells in birds that were relatively free to move about and behave naturally.

"The single-neuron recording gives us a powerful tool for the study of sleep's importance to learning," said Margoliash.

The researchers were able to record the firing patterns of individual pre-motor brain cells of four zebra finches, a well-studied songbird native to Australia that weighs only about half an ounce.

The male zebra finch works hard to attract the female with his stereotyped song, and the brain structures that control singing are highly specialized for this behavior.

The researchers compared the activity of each neuron while the awake bird sang, while a sleeping bird could hear a recording of its own song, and during undisturbed sleep.

While the birds are awake and singing, the neurons fire in a pattern that is unique to the note and syllable components of each bird's individual song. When the awake bird hears its own song, these neurons do not fire in response.

But in the sleeping bird listening to a recording of its own song, the neurons do fire in the pattern identical to song production, though the bird produces no sound. This pattern of firing during listening, like the pattern of firing necessary to produce song, actually anticipates the next song "syllable," or set of notes.

"The learned song is a temporal code that uses the nerve impulse spikes of single cells in precisely matched patterns for hearing and singing. The two patterns can be 'mapped' to each other with spike-by-spike precision," said Margoliash. "The bird is using the preceding sound to predict how to generate the next syllable." Understanding how patterns of behavior are represented in the brain has been a major problem for neurobiologists.

"Previously we found that during singing, song is represented as a temporal code. Now, much to our surprise, we find this correspondence in single cells of matched sensory and motor patterns. Forming this mapping of sound and action is the process of learning," said Margoliash.

"Our results demonstrate that individual neurons replay complex activity during sleep that they produced during waking," said Margoliash. "This storage and replay could help adult birds maintain accurate copies of their songs, and help young birds to learn to sing."

During undisturbed sleep, the researchers discovered, the neurons spontaneously fired the same complex song production patterns in bursts. Interestingly, these activity patterns were at slight variance, as if the bird was rehearsing a variety of slightly different songs, sometimes with slower or faster tempos.

How does the bird learn to correct its song when, by the time it hears it, the neuron is now engaged in the production of the next sound? Practice during sleep may be part of the answer.

"In contrast to the prevailing idea that it learns by making moment-to-moment adjustments, we think the bird stores the song production pattern and reads it out at night, an "offline" solution to the timing problem," said Margoliash. "The zebra finch can replay and strengthen the pattern during sleep."

The next step, according to Margoliash, is to explore what happens to song learning when the sleep replay is interrupted. "If we can describe the rules by which sleep acts on song learning, these lessons may apply to learning in other animals, including humans," said Margoliash. "Neurobiologists have often found that lessons learned from weird and wonderful animals apply to all animals. The beautiful songs of birds could have much to teach us about how we learn."

Yesterday I shed three tiers

A correction: Yesterday when observing the huge numbers of grackles and starlings roosting in the trees around the Pulitzer Fountain, I wrote that the fountain had three water-filled tiers where the grackles drank and bathed before roosting. Today I watched the roosting drama from a bench a few feet away from the fountain, rather than from across the street . I could now see that there were six circles of granite, not three. The birds only used the top three, however.

Tuesday, October 04, 2005

An awesome spectacle -- but nobody notices

Pictured above is the three-tiered granite fountain surrounded by a half-circle of Linden trees standing in the large open area directly in front of the Plaza Hotel. It is officially called the Pulitzer Fountain, named after its donor, Joseph Pulitzer - the man who is better known for the prizes than the fountain he donated to the city in 1916.

Tourists, who abound in that area just south of the southern border of Central Park, seem to know the fountain's real name, as well as the official name of the large open area in which the fountain stands -- the Grand Army Plaza.New Yorkers simply call it the Plaza fountain and the plaza outside the Plaza. [To the fountain's north there's a large gilded statue of William Tecumseh Sherman, Civil War hero, which might explain the plaza's official name.]

Few, if any, of the hundreds of tourists passing by the fountain these days between the hours of six and seven, nor the many New Yorkers hurrying home from work at that time, pay the slightest attention to an awesome natural spectacle happening all around them as they pass by: A stream of at least a thousand --- yes, I mean 1000 birds come flying out of the south-east corner of Central Park just across the street from the Plaza and its plaza to roost for the night in those ten Linden trees surrounding the fountain.

The birds are all European Starlings and Common Grackles. There seem to be more grackles than starlings, although there are so many of them that it's hard to keep track. One great behavioral difference distinguishesthe two species, however: many, or most, or perhaps all the grackles stop at the fountain to drink and bathe before heading for their night roost. Around 6:15pm there are grackles around all three tiers of the fountain, splashing and drinking. As some fly into the trees, newly arrival grackles head for the fountain. But not a single starling may be seen among the grackles at the fountain. Why? Nick Wagerik had a thought: perhaps the birds' differing diets might make grackles thirstier than starlings.; i.e. perhaps starlings' food has a greater water content. I'll welcome any theories readers might have.

Scanning the trees from a bench across the street, I can see that the birds at the tippy-top of the trees are all starlings. But as night falls there is a lot of jostling and changing of positions of the hundreds and hundreds of birds in each tree. I'm not sure who ends up where.

Like at the American Robin night dormitory I've been monitoring since last April, once dark sets in it's hard to find the sleeping birds, even with a super- strength flashlight like the Sure Fire I use. I can usually find two or three.
They do not seem to tuck their heads under their wing when they sleep, as in story and song, neither the robins nor the grackles. They scruntch their heads into their necks, somehow, so the beak seems to be pointing up.

I monitored this amazing influx of birds last Sunday and Monday. The birds start arriving in small numbers by about 5:45 pm. By six they were arriving in groups of twenty or thirty. By 6:15 they were arriving in great numbers; there'd be a little pause, and then a thick cloud of birds would arrive -- perhaps one or two hundred at a time. Even more seemed to arrive at 6:20 and 6:25pm, when the light is fading fast. By 6:35 the numbers were diminishing. By 6:45, with the street lights going on up and down Fifth Ave, and the large fixtures outside of Bergdsorf's and the Sherry Netherland and A La Vieille Russie at 60th Street already brightly shining, the last birds could be seen straggling in. And then no more.

Though it is quite dark by 7 pm, now a tremendous din of bird squeaks and calls and cackles coulod be heard under the trees, slightly masked by the sounds of the fountain. All the birds were now in their roost trees, but they were not asleep.

I have no idea what is the purpose of all that noisy chattering before they settle down to sleep. For all I know they are wishing each other Good Night and pleasant dreams. In fact I have no idea about whether birds even dream.Tthere seems to be very little known to science about birds' sleep.

One thing I know: this exciting event is going on night after night in a busy, crowded part of the city, and almost nobody is aware of it.
It's not necessarily that people are not interested. It's that this huge number of birds somehow does not penetrate the human consciousness unlesspeoploe are alerted to it as I was by Ben. I've probably passed by that very spot on a number of occasions and noticed nothing.

PS As I noted in an earlier post, it was fellow birder Ben Cacace who first discovered the grackle night roost and alerted me to its location.

Mind-blowing metamorphosis sequence

Monday, October 3: I met Nick Wagerik at the Shakespeare Garden at about 1:30p.m. The Black Swallowtail caterpillar seemed pretty much unchanged. I took the photo above at 1:48. At about 2:15 Nick headed for Turtle Pond to check out the dragonflies. I stayed in the garden for a few more minutes hoping against hope that I'd see something happen. Nothing at all happened and I left the garden at about 2:30.

Lloyd Spitalnik [with camera] ran into Nick at Turtle Pond around 4. Nick told Lloyd about the caterpillar and they decided to walk back to Shakespeare Garden. [It's very near Turtle Pond.]

Just a little before 5 the drama began. Lloyd caught it all on camera and sent me the photos to post. Here they are with the exact time codes from his camera to give you an idea of how quickly it all happened.:









4:58:04 The last photo. [The pupa will overwinter, and the butterfly will emerge next April or so].

Welcome to Shakespeare Garden, beautiful butterfly of the future. We'll be keeping an eye on you.

Note: Lloyd's website may be found at

What nuts was Little Red caching?

photo by Lloyd Spitalnik
Little Red with his favorite nut

Bill Trankle from Indianapolis, writes [in answer to my question a few days ago]:

Marie, those nuts in Sunday's picture look like black walnuts to me. I have several of those trees around my yard, and the nuts come encased in a green woody cover (when they're fresh; they eventually rot to brown as some in the picture are doing) that the squirrels have to chew through. As you can see in the nut at the upper right, the casing surrounds a typical walnut-looking hard shell that the squirrels will grind through (very loudly!) to get to the meat. I've heard these walnuts aren't very tasty for humans, but I've never tried them myself. A problem I have is that the squirrels will chew through the stems of these nuts to get them to fall so they may collect them and cache them at their leisure--I've nearly been hit multiple times by these bombs, and from the impact they make I'm sure it would be quite a painful experience!

Bill Trankle

PS from Marie:

Bill's right. I've confirmed with the park's tree people that the squirrel has chosen one of the park's most valuable trees, a Black Walnut ,
[Juglans nigra] for its headquarters. According to a tree inventory taken in 1982, there are 23 of these trees in Central Park. This one is west of the Great Lawn.

PPS Bill, I've heard that the nuts are delicious, if you're willing to do all the work to get them.

Monday, October 03, 2005

A visual challenge

Here's the lattice-work fence [probably bamboo, not wood] to which the Black Swallowtail caterpillar has attached itself in preparation for becoming a pupa or chrysalid. As of 1:30 pm today, when this photo was taken, pupation had not yet occurred.

Challenge: Can you find the caterpillar on the latticework?

Hint 1. It's green, about the same green as the background plants; the other colors don't show.
Hint 2. It's in the upper half of the photo.
Hint 3 It's just to the left of the only piece of latticework that is vagely parallel to the rusty metal support at the right.
Final hint: It's hanging on the underside of a piece of latticework going from upper left to lower right.

Found it? It's hard, even in real life when you can see the colors and spots. But that's good. This is the most vulnerable part of its life cycle. How one of the many birds in Shakespeare Garden would love to make a meal of it.

The caterpillar's girdle

Very slim pickings at the Moth Tree last night, two small triangular-shaped moths called Common Idias and one Large Yellow Underwing, a very common exotic insect that is actually not an Underwing at all. That was it.

Then Nick Wagerik mentioned that a Black Swallowtail caterpillar had been seen at the Shakespeare Garden earlier in the day. Maybe it had begun its transformation into a chrysalid. It would spend the winter in that form and release its butterfly sometime next spring.

At about 8:30pm we abandoned the moths and headed for the garden

We found the striking larva easily. It had picked a very familiar [to us]spot to pupate --- a slat of a latticework fence directly in front of the bench where the Central Park non-maternal Mothers always set up their black light on hot summer nights.

Unlike the Monarch caterpillar, that spins a chrysalid hanging from a plant stalk [see previous website entries -- 9/20 and earlier] the Black Swallowtail caterpillar attaches a chrysalid to a stalk -- or in this case, a wooden slat, by means of a "girdle" encircling its body. You can see the girdle thread going from the caterpillar to the slat at the upper right part of the caterpillar, near its head. It looks like a thin thread. The part of the girdle that goes around and then attaches on the other side cannot be seen. It is under one of the folds of the larva's back.

The stunning pale-green, yellow, and black creature has not pupated yet -- that is, it has not transformed itself into a chrysalid. But it will do so soon -- it has definitely attached itself to the latticework fence. The transformation is extremely fast -- less than a minute, Nick says. I hope I'll manage to see it. I'll be at the garden with my little camera early this afternoon to check out its progress. Very exciting.

Sunday, October 02, 2005

Where do Grackles sleep at night?

The photo below, taken by Cal Vornberger last July, portrays two subjects of particular interest to me : 1. Grackles, whose night roosts I 've been looking for and now, thanks to Ben Cacace, I've found - see letter below- and 2. Moths.

In the photo, a parent Common Grackle is feeding a moth to a hungry nestling. It's hard to tell, but the bit of moth visible suggests it might be an Underwing.

Ben Cacace wrote:

DATE: Friday, 30 September 2005
TIME: 5:22p-7:00p)
LOCATION: Central Park - The Pond &
Hallett Sanctuary (se. corner)

A Common Grackle roost was found near the south end of Central Park. While birding in the area around Gapstow Bridge, south of Wollman Skating Rink, I watched grackles & starlings flying towards the southeast corner of the park. The birds were heading out of the park towards a group of 10 trees surrounding a water fountain just east of the Plaza Hotel. I started watching the stream around 6:20p. The number of birds
reduced to a trickle shortly after sunset (6:45p). The last bird seen entering the roost was around 6:54p. The number was close to uncountable. They were flying in so densely that only an estimate could be given of the groups and multiple observers would be needed to
come close to separating the starlings from the grackles. The number of roosting birds is huge but the difficultly in counting them is huger. My estimate for the short time I spent on the plaza across from the Plaza is a few thousand. The ability for this many birds to settle in such a small number trees with plenty of room for many more is simply amazing.**

PS from Marie:

I'll be checking out Ben's Grackle roost tonight, and I'll post a report tomorrow on what I find.

The Red Squirrel's Cache

Lloyd Spitalnik sent the photo below yesterday and wrote:

This is what the base of the Red Squirrel's tree looks like. It's been a very busy creature.

PS From Marie

The nuts look like pignut hickories to me. Any other ideas?