This Saturday is Count Day, the 16th annual State-Wide Spring Bird Count. About 1,500 birdwatchers, 150 of them in Cook County, will be out all day counting the birds passing through Illinois as the northward migration nears its peak.

For decades, birding was a sport with one major annual tournament: the Christmas count. The first Christmas count was held in northern New Jersey in 1900, and since then, with the active backing of the National Audubon Society, the idea of a winter census has spread all over the world. About 40,000 people take part in Christmas counts now, enumerating the birds in much of North America and in pieces of all the other continents.

There is, however, a certain irony in Christmas counts. Birders, whose goal is to see as many birds as possible, have scheduled their major event for the time of year when birds are scarcest. Count compilers in this part of the world feel pretty good about any count that produces more than 70 species.

In May, we have a shot at 200 species and thousands of additional individuals. Also, you don’t spend as much time shivering in May as you do in December. So the idea of a spring count spread to birders around the country over the last 20 years. Many states now hold them. The sponsors are either state conservation departments, as in Illinois, or state ornithological and Audubon societies.

The Illinois count is organized by counties and depends entirely on volunteers. Each county has a compiler who is supposed to find birders, assign them to territories before count day, and then add up their results after count day. This year will be my fourth as compiler for Cook County, and I may hang up my phone list after this one. Getting 150 birders out in the places they are supposed to be on count morning can eat up a big piece of your life. So can adding up the results on all those field reports.

And you have to be patient dealing with volunteers. People will do what they want to do and if you want them to do more, you have to convince them. Patiently explain, as Lenin used to advise. But this year I often find myself tempted to lapse into a Prussian accent and start barking orders. “You vill begin birding no later than 0520 hours; you vill bird this entire sector thoroughly and have a full report on my desk Monday morning.”

The really strange part is that I’m trying to get these people to go birding, something they are supposed to like to do. It’s not like I’m looking for volunteers to mow the cemetery.

Having undergone a startling metamorphosis in the past ten years, from footloose bohemian to Dagwood Bumstead, I truly appreciate the opportunity the count offers. For that day at least, birding takes precedence over household minutiae. “Normally, dear, I’d love to shop for new bathroom tile, but I’ve got the State-Wide Spring Count tomorrow.” I like to deliver a line like that with my face set in a square-jawed, duty-is-a-stern-mistress sort of expression.

Great claims are made for the scientific value of the information we collect on a spring count, but I think the claims are a little dubious. Certainly census information from the Christmas count has been used to help plot the winter ranges of various birds, but birds in winter are somewhat sedentary. Birds in May are on the move in a big way, so a one-day count may not provide enough information to characterize the migration season.

Birds with long, energy-consuming flights to make will wait for favorable winds whenever possible. They will feed and rest while the wind is from the north, but if a warm front passes through bringing south winds in its wake, they immediately take to the air. To an observer on the ground, the migration appears as a series of waves. The crests are the concentrations of birds that follow warm fronts. The troughs are times of north wind when the birds are spread out and less conspicuous.

So the presence or absence of a particular species on a particular spring count doesn’t mean a whole lot. Maybe if the count had been held the next day, the absent species would have been ubiquitous.

Some professional ornithologists mistrust all counts held by amateurs because there is no way to be certain of the competence of the observers. It is true that the skill of our bird counters varies widely, but I suspect the same would be true of any group of 150 holders of PhDs in ornithology. We don’t use absolute beginners on the spring count. The likeliest mistake for our less skilled people to make is to miss a rarity because their eyes are not experienced enough to notice a rare bird amid common species of similar appearance. The possibility of seeing a rarity is a major part of the fun of the count, but it is not where the scientific value would lie.

There are also problems with counting each individual bird you see. Try it the next time you go for a walk in the park. Within 30 seconds you will be tormenting yourself with questions: Is that the same sparrow I just counted, or is it a new one? My guess is that we do pretty well with the less common species and that a mixture of overcounting and undercounting balances out on the common birds.

Last month, Elaine Vercruysse of Chicago Audubon had the tedious job of feeding the results of all our past counts into a computer. The machine spat things out in a nice, convenient form. Looking at the results, I would say that the spring count has taught us things, but they were things we already knew.

Consider the Canada goose. The Canada goose used to be seen around Chicago only as a migrant, and its migration was early in spring. By May, the geese were on their nesting grounds in the far north. In 1972, the first year of the count, only ten birds were reported, and in 1974, only seven were seen.

But then the giant Canada goose was rediscovered. This large, sedentary race of the species used to breed in the midwest, but for a time it was thought extinct. After its rediscovery, it began to be introduced in several states. Suddenly, we had a resident population of Canada geese in the Chicago area. Last year, we saw 808 birds on the spring count.

The count plainly shows the rise of this bird, but no local birder needed a computer printout to tell him that the status of this species had changed. We all knew it already.

The computer also told us that 246 species have been reported at least once on the Cook County count. Ninety-nine have been seen every year; another 27 were reported on 14 out of 15 counts. Seventeen species were seen only once. We have in the 15 years, enumerated 259,622 individual birds.

If the count is not much as science, you may wonder why we do it. The answer, of course, is fun. It is a game, a pleasureful task we have set ourselves, and like all games it is an end in itself, something you do because you want to do it and not because it might win you a Nobel Prize someday.

It does have one further benefit. It advances the sport of birding. Like model railroaders and collectors of old comic books, birders are an affinity group, a disparate collection of people held together by a common passion. Events like the spring count sustain the group. They bring new people into it and keep alive the interests of older hands.

If Cook County wasn’t such an enormous place, I’d organize a party for count night. There are a lot of Christmas counts where the party is the best part. You get a chance to swap stories with other birders; the new kids get to meet the established stars of the game, and the discoverers of rare birds get to bask in the admiration of their fellows.

Maybe the ultimate value of events like the spring count is that they inspire birders to get good enough and interested enough to undertake a census of nesting birds, a project that very definitely has scientific value. Or maybe I should just go look at birds and not worry about redeeming social importance.