Each year, I spy the first sparse flocks of whimbrels, marbled godwits and long-billed curlews, freshly arrived from their summer roosts in Canada, muscling turf away from San Diego's perennial shorebirds. These three fascinating species have long been favorites of mine, and I have devoted many a delightful morning to uncovering the subtleties of their behavior. Sadly, some of my fellow bird-watchers roll their eyes in disbelief when they see me setting up my little laboratory on the beach. For example, I'll often dash in and take over a spot where a flock has just been feeding so I can make measurements of their bill holes, footprints and droppings.

This kind of active scrutiny, aimed at quantifying the behavioral patterns of these animals, tends not to sit well in a community more used to observing birds passively through binoculars. But to discern complex relationships, a naturalist must carry out numerical measurements and chart the results. All professional scientists know this truth. Yet few amateur bird-watchers are aware that they could do even more to advance the scientific understanding of the natural world by quantifying their observations. So this month I offer a few ways to give bird-watching some quantitative teeth.

Although I developed these methods to examine California's shorebirds, the techniques are quite general and can help you to study the birds living in your neck of the woods. (In fact, similar methods could also serve in studying many other kinds of small creatures.) By comparing observations of many different species, interested amateurs might be able to separate behavioral patterns that sprang up recently from those that emerged early in the evolutionary history of birds, perhaps 100 or more million years ago [see The Origin of Birds and Their Flight, by Kevin Padian and Luis M. Chiappe].

A good place to begin is by studying the traces birds leave on the ground. The best way to determine the relative location of such bird markings is to use a portable grid. Although a grid makes it fairly easy to draw a representation of the site on a sheet of graph paper, I suggest you use a camera instead. You can collect information most effectively if you spend your limited time in the field photographing interesting sites and then logging the observations in a notebook after the pictures have been developed.

To maintain accuracy, read the position of features on your pictures carefully using a ruler. Stay away from cameras that project an image of their own internal grid directly onto your photographs. That grid is always the same size on the film no matter how far away the subject, which makes it difficult to compare several pictures of the same site taken from different vantage points.

A nylon fishing net with a diamond-shaped mesh is ideal, because by tugging on it you can make the openings square. The size of your survey area will determine the optimum size of your mesh. If you are studying areas of a few square meters, a net with a five-centimeter mesh (about two inches) that is approximately three meters (about nine feet) on a side works well. Spray-paint the net a color that will stand out in your photographs. At your field site, secure one corner of the net using an old tent stake. Then use an L-bracket to guide the mesh into a square grid as you stake down the other three corners.

I do much of my research on the beach and have had a terrible time with joggers mindlessly running through my survey areas. They would often tramp directly on the site--even while I was standing there making measurements. I finally solved the problem by erecting a barrier around the perimeter with four vertical tent poles spanned by yellow-and-black "caution" tape.

To make grid coordinates obvious, obtain a set of numerals from your local hardware store--the kind used to indicate the addresses of houses. These tags will enable you to number the vertical and horizontal axes in a way that will show up in your pictures. The separation between the numerals will depend on the size of your site. Position them closer together (separated, say, by two or three mesh units) for a small site and farther apart (perhaps five or more mesh units) for a larger survey area. It never hurts to place an arrow and the letter N (also available from your local hardware store) in the frame to indicate magnetic north, so take along a compass.

Subtle features on the ground, like footprints or bill holes, are difficult to see in a photograph. Colored plastic poker chips provide a handy solution. For instance, suppose there are seven separate but tightly bunched bill holes in the sand. Mark that spot with a poker chip clearly labeled with the numeral 7 drawn on an adhesive note with a broad-tipped black marker. A photograph of the site then documents the position of the chip on the grid and the number of feeding holes at that location, even though the holes themselves might not be visible. Indeed, you can easily record different markings--bill holes, droppings, footprints--using a different color chip for each. Or you can dye some clothesline a bright color and use it to trace outlines around features of interest.

If a particular area needs a detailed explanation, a poker chip carrying a special mark (say, an asterisk) can refer to an entry in your field notebook. Be consistent with your use of colors for poker chips and clothesline. It doesn't matter what color scheme you adopt, but establish some convention and note it clearly in your notebook.

The illustration shows a feeding site for a group of 22 whimbrels. Diagrams such as this one allow amateur naturalists the opportunity to unravel fascinating details about these birds. For instance, my observations indicated that the number of droppings per unit area is much greater outside the feeding zone than inside it. This arrangement suggests that whimbrels have evolved not to defecate where they eat--a strategy with obvious advantages. By knowing how many birds fed at this site and for how long, one can estimate the average number of droppings produced by any single bird feeding here per unit of time, which, though maybe not the most pleasant thing to think about, is a basic biological indicator of the health of the population.

The markings made at feeding sites such as this one are easily captured with a few photographs. But for recording the actions of animals as they happen, nothing beats a camcorder. You will want to have a protective carrying case, at least two extended battery packs and a tripod. Zoom capability, which lets you close in on your subject without actually moving toward it, is also helpful. But avoid the temptation to take only close-ups. Recording wide-angle views may allow you later to observe behavioral patterns of a group that you missed in the field.

Recently, after looking over some footage of a small flock of whimbrels feeding at the beach, I noticed that these birds showed a remarkably strong herd instinct. One bird started feeding, and in just 40 seconds the entire flock joined in. Several minutes later a different bird started bathing in the surf, and in less than a minute all the others had shifted from feeding to bathing. Then came group preening, then ear scratching, then head shaking. Over the course of an hour, the flock stepped en masse through six distinct activities.

Having the videotape made it child's play to see what was happening. The speed at which the group shifted between behaviors [see graph above] was striking. Why have these birds evolved to act in this way? No one knows, but perhaps with a coordinated study, dedicated amateur bird-watchers can help solve the riddle.

For more information about this and other amateur science projects, visit the Society for Amateur Scientists's Web site. You may also write the society at 5600, Post Road, #114-341, East Greenwich, RI 02818, call 1-401-823-7800.

The Society for Amateur Scientists (SAS) is a nonprofit research and educational organization dedicated to helping people enrich their lives by following their passion to take part in scientific adventures of all kinds.