Archive for July, 2011
- December 2011|
- November 2011|
- October 2011|
- September 2011|
- August 2011|
- July 2011|
- June 2011|
- May 2011|
- April 2011|
- March 2011|
- February 2011|
- January 2011|
July 22nd, 2011 | Meera
The Science Essayist is volunteering at a bird observatory in Sweden this summer.
Leaning over the work table in one of the observatory’s ringing huts last week, I raised a hand to smooth the lists of birds we keep pinned to the wall. They show each of the dozens of species we might encounter here: its common names in English and Swedish, its scientific name, the five-letter abbreviation by which it is identified in our protocols, and the standard ring size it takes.
(An aside: Some of the abbreviations assigned to bird species are tiny bits of sound-poetry, delicious to say. I like it when we catch a Redpoll, and not just because they are beautiful birds. Their code, derived from the scientific name Carduelis flammea—Redpolls are also known as Acanthis flammea by some taxonomists—is like the politest little cough. CAFLA!, I announce happily as I write it down. CAFLA! Forgive me; I have something in my throat—CAFLA, CAFLA, CAFLA.)
I don’t know if my fellow volunteer Peder saw my wedding band glinting as I stood with my hand on the wall. But perhaps that’s why he said at that moment—his voice rich with the delight of a clever observation—”But Meera’s been ringed. What size is your ring, Meera?”
I smiled, both because I like Peder’s sense of humor and because there was pleasure in taking his question, which required no serious answer, seriously.
What size was my ring? Did it conform to the requirements of comfort and utility assigned to every ring we put on a bird in this hut? Was it loose enough to slide easily up and down my finger, but snug enough not to fall off? When it was placed, did someone take care not to harm me? Was it unobtrusive, in no way impeding my flight, feeding, or other natural behaviors? Did its presence on my finger serve a meaningful purpose in the world? And could you trace my history by it?
I don’t remember what I said to Peder then, twisting my ring affectionately and thinking on these questions with ducked head and wondering mind. Today—watching my brown hands fly over the keyboard, marked by a flicker of white gold—I am still sitting with them.
But when it comes to the birds, at least, I have some answers I can give.
Many of you reading have first-hand experience with the processes and purposes of ringing (or banding, as it is called in the U.S.). You, friends, don’t have to stay for the rest of this post—although I would love it if you added a comment or let me know how you do things. For the rest of you—and for me, since I am learning these things along with you—I have written a small primer. Ready? Grab a fika. This will be long, and though I find it fascinating, it won’t be very poetic. Something sweet will help us all stay focused. :)
A Bird in the Hand
To work with a wild bird, of course, you must first have access to it. If you are ringing birds in nest boxes, as I was helping Stefan do earlier this summer, this is fairly straightforward. You simply check each nest box periodically, noting which are occupied, which have eggs, and later, which have nestlings in them.
If you know approximately how old the chicks were when you last checked on them and how old they will be when they fledge, you can pick a day to ring them—sometime when they’re well grown, but not quite ready to leave the nest. At that point, you can safely pluck the clutch of nestlings out one by one, ring them, and put them back inside. Depending on the species, you’re more or less likely to be able to ring the mother as well—flycatcher parents tend to flee the nest when you approach; tits sometimes stay inside.
Besides nest box ringing, the observatory also conducts mist-net ringing each summer. (This is what I’ve been helping with for the past few weeks, since the Great Snipe tracking began winding down.)
Mist nets are very fine nets constructed of strong black nylon, with mesh sizes that vary from about 16mm to about 120mm; you need a larger mesh to catch big birds like waders and raptors, and a smaller one to catch little birds like warblers and finches. The nets get their name, as you might imagine, because when unfurled they become virtually invisible to birds (and preoccupied humans, as I have proven on more than one occasion).
Each net comprises five vertical sections of netting separated by five horizontal threads; you set it up so that the horizontal threads run taut between two poles and the vertical sections hang loosely below them, forming several pockets into which birds can fly. Nets are usually set up in the early morning and taken down or rolled up in the early afternoon. In between, birds are active but the sun isn’t shining down too hard. If it becomes very hot, windy, cold, or rainy when you are using mist nets, they are promptly closed so that you don’t trap birds under adverse conditions.
Amazingly, I have no unfurled mist nets among the nearly 500 photos I’ve posted of Sweden so far. Here is one from my wonderful Flickr contact Andy Jones, of the Cleveland Museum of Natural History. Ours look exactly the same, but surrounded by tall grasses and wildflowers.
Once you’ve opened a net, it is checked frequently so no bird remains caught for very long. The great majority of the time, birds become only lightly tangled, and removing them takes moments. Occasionally a bird will be more difficult to extract (in tricky cases, beginners like me should always call for help from more experienced ringers, so that the bird can be freed as efficiently as possible). Either way, you follow the same basic steps. First, determine which side of the net the bird entered on, and work on that side; next, free the feet, then the wings, then the head, since that’s the opposite order from which most bird parts encounter the net.
The removal process, though usually straightforward, is the most delicate part of the ringing operation. It requires patience, care, and a constant attention to the welfare of the bird you’re working with. You may be being swarmed by mosquitoes or gnats or tiny evil flies, for instance, but if you have a bird in hand, you can’t twitch an arm suddenly to shoo them away. (Me, if this gets very bad, I swear under my breath. I don’t think anyone but the birds has heard me yet.)
Once you’ve freed a bird, it is placed inside a cotton drawstring bag and taken somewhere else to be processed: in our case, a ringing hut.
A Minute of Science
While there are many steps in processing a bird, experienced hands can perform them incredibly quickly—usually in under one minute. It will take me longer to write about this and you to read it than it takes most birds to make their way out of the ringing hut, and I’m not even going to describe the steps in detail, just list them.
The first thing a ringer does after removing a bird from its bag is identify it. This dictates the ring size it will take, because that is dependent on the average diameter of each species’ leg. The smallest ring we have is a 0.5, which we put on tiny things like chiffchaffs; the largest, spares of which we own but almost never use because our operations aren’t designed to trap anything except songbirds, is a 93—for something magnificent like a crane.
Next, the bird is ringed using a special set of pliers with round openings. These help you to properly bring the edges of the ring together without any danger of squeezing the bird’s leg. I have seen experienced ringers do this so smoothly that I am barely ready to write down the ring number before they are done.
Finally, several pieces of information are taken that will be associated with the bird’s ring number.(Every country in which birds are ringed has a central database to which these records are uploaded.) Here, we sex and age the bird to the degree that this is possible using physical signs, and then take a fat score, a wing measurement, and weight. We also look for the presence of a brood patch (a wrinkly, swollen area on female birds’ bellies that indicates they are in nesting mode), and determine what stage of feather growth young birds are in and what stage of moult, if any, adult birds are in. None of this data is necessarily all that significant in isolation, but collecting it for millions of birds worldwide each year adds a tremendous amount to the knowledge we have about various species.
If an already-ringed bird is captured, all the same information is collected and its ring number taken down. When that record is uploaded, whoever ringed the bird originally is automatically notified, so they know where that individual has been. I imagine it must be rather thrilling to receive one of these notices. Perhaps it’s a little as if a message you’d put in a bottle had been found across the seas.
After all this, the bird—which, if it is typical, has stayed calm throughout—is released through a small hatch in the side of the hut. Or, if it is a fledgling, it is taken back to the area where it was caught, with its siblings if any were trapped at the same time. We do this so that young birds can easily find their way home. I have returned fledglings several times and I can’t tell you how reassuring it is to hear chicks and parents calling to each other as you approach their nest.
As I said, most often a bird is held in the hand for less than one minute. (It took me about 15 to write this, but things might have gone a little quicker if I hadn’t run out of coffee one section ago. How are you doing, by the way? Any fika left? I’ll try to be quick now, although this last bit is arguably the part I most want you to understand.)
Varför Vi Gör Det (Why We Do It)
It’s all very well to tell you what we do when we ring birds; what perhaps seems even more mysterious, at least if you haven’t thought about it before, are the reasons we do it at all. A dear friend—and I hope she doesn’t mind me quoting her, because I think her words reflect what’s in many people’s minds—commented last week on a photo I posted of a female chaffinch being processed: “I get science and all that, but from a bird perspective, where you are must be a torture chamber.”
Let’s talk about that second part first. It’s perfectly true that being caught in a mist net and ringed is no bird’s idea of a pleasant morning. To a human, handling birds is a fascinating and rewarding experience. It’s hard not to be emotionally affected, even if in a restrained and professional way, by the physical fact of a live bird in your hand. Feather to skin, a bird’s warmth, heartbeat, and softness transmit themselves directly to you in a way that can feel electric.
To a bird—there’s no getting around it—a ringer is a predator.
Having said that, most of the birds we trap are likely to have what are obviously far more dangerous encounters with actual predators every day. Many are migratory species which travel thousands of kilometers each year and face the most grueling environmental conditions. Birds are by constitution tough animals, capable of weathering stress—especially if it is temporary and causes no physical injury—very well.
I will not lie to you. The risk of physical injury does exist. But I believe it is safe to say that the overwhelming majority of the millions of birds ringed annually, under the supervision of ringers licensed by their home nations, emerge from the process completely unharmed.
If I had written this post a few months ago I wouldn’t have been able to make that statement as confidently, but thanks to a recently published study, beautifully unpacked here by a science writer I respect a great deal, I can tell you that when the records for over 600,000 mist net captures in the United States were analyzed, the average rate of injury (which includes events like wing strain, cuts, stress, or broken bones) was found to be less than 0.59%, and the average mortality rate about 0.23%.
While those numbers are extremely low, they would still represent an unjust harm to bird populations if ringing served no useful purpose. But it serves many—too many, in fact, to describe here in detail, especially since I am quite sure you are now, like me, entirely out of cookies and tea (I switched to tea a little while ago).
Here then—highly abbreviated—is a short list of scientific and conservation-related reasons birds are ringed:
• Ringing is the primary method of understanding bird migration. (Before the advent of ringing as a systematized process, migration was a deep and myth-producing mystery.) By recovering previously ringed birds at different points on their migration pathways, we can identify important nesting, wintering, and feeding grounds, and note changes in routes. Such knowledge is not only interesting for its own sake, but an important advocacy tool for conservationists seeking to preserve habitats or demonstrate the effects of human activity or global warming on bird populations.
• Ringing is the only way to gather data on the lifespan of individual birds and thus establish longevity records for bird species in the wild.
• Ringing and recapturing birds in the same site over a sustained period can enable us to roughly determine how many birds exist in a given population, as well as how well they are surviving and breeding. Ringing can also help to pinpoint the reasons for population changes. For instance, if a particular species is becoming rarer, but we know from nest box studies that it’s successfully nesting and raising chicks and we know from mist net ringing that the rate of juvenile survival has gone down, then we know that some condition affecting young birds, but not affecting adult birds’ capacity to breed, is responsible for the population decline—and we have a better idea of where to look next.
• Ringing game birds is vital for monitoring the impact of hunting and determining if existing regulations are effective or should be changed.
As I write, I can feel the cool contours of my own ring embracing my finger. Beyond its shape it bears no other resemblance to the small aluminum or steel bands we put on birds, except for one: both represent a promise from those who put them on.
Of the promise that was made to me, nothing more need be said. I appreciate it every day.
Birds, of course, have no such feeling about the promise their ringers make to them. But I believe it exists, despite this, in the closing of each circle around each protesting leg. To me it seems at heart a very simple vow: to know, to heed, to protect, to remember, and to look for again.
July 16th, 2011 | Meera
The Science Essayist is volunteering at a bird observatory in Sweden this summer.
Since I had it ever-so-subtly pointed out to me today by a good Swedish friend that I had not—despite my promise to spend the summer writing—made a new post here in what was deemed too long a time, I hereby make the following solemn pledge to you all.
Come back in a few days, and I will tell you a little bit more about the steps that go into processing a bird that you catch in a mist net, the physical act of ringing, and what it’s been like for me to handle live birds. I hope that will satisfy. :)
In the meantime, in case you haven’t been following the journey on Flickr, I have this for you, too. Don’t we all feel like this sometimes—capable of crossing the world on our wings, if only something weren’t holding tightly to our feet?