We were thinking recently about the impact the nearly 600,000 acres of land protected over the years through the Land for Maine’s Future (LMF) program has had on birds. The reason why this popular conservation program has been on our minds is because of the recent announcement to kick-start the program again, which languished for the last eight years under state leadership that refused to fund it, despite voter-approved bonds to do so. Currently, there’s a push for $95 million dollar bond proposal, $75 million of which would support LMF, with the other $20 million to address long-overdue infrastructure problems at Maine’s State Parks — a great idea and one we hope will come to pass.

As we considered the benefits to people and wildlife provided by the acres of land protected by the program over the decades, we wondered if we could get a ball park figure on how many birds those nearly 600,000 acres might be protecting. We started off by considering the birds that nest in our own half-acre yard. Most years we have at least a pair of American robins, a pair of song sparrows, a pair of black-capped chickadees, and a gray catbird couple. Those are the ones we know of. Although we have bird- and pollinator-friendly gardens, blueberry bushes, a raspberry patch, shrubbery, and a brush pile, our yard is proportionately taken up by lawn, which is not prime bird habitat.

But even so, we host eight birds in a half acre, so presumably that would translate to about 16 breeding birds per acre. To be conservative, let’s use the figure of 16 birds per acre as an average number breeding even in not-so-good habitat. Now apply that number to the 600,000 acres of land protected by the Land for Maine’s Future program. That would mean that the program is protecting land for 9.6 million birds!

We may never know the true number of birds protected through this program but even this simplified mathematical exercise shows that it has to be a very large number!

One way ornithologists get good estimates of the number of birds breeding on a particular plot of land is by using a technique called “spot-mapping.” It’s actually a pretty common-sense idea that takes advantage of the fact that most breeding land birds, especially males, defend territories from other males. The territory boundaries of each male tend to stay pretty static through a single breeding season. An observer can go out and observe singing males, noting the precise location on a detailed map of the area, especially when two or more are singing near each other (presumably near a territory boundary). Repeat multiple times over a breeding season and a clear pattern usually develops that shows the outline of each bird’s territory. Plot all of the observations on a single map of the area of interest and you will then be able to count the total number of territories. That number, averaged over the total area surveyed, will then give you a density—the number of males per acre.

Just for fun, consider trying this around your yard or neighborhood, maybe just keying in on one or two species using a map printed off Google Maps. You may be surprised to find out how many pairs of robins or chipping sparrows have established territories in your midst.

You may also gain an appreciation for the critical importance of land protection efforts, like those of the Boothbay Region Land Trust and others, that will be funded by the proposed bond funds for the Land for Maine’s Future program.

Jeffrey V. Wells, Ph.D., is a Fellow of the Cornell Lab of Ornithology. Dr. Wells is one of the nation's leading bird experts and conservation biologists and author of “Birder’s Conservation Handbook”. His grandfather, the late John Chase, was a columnist for the Boothbay Register for many years. Allison Childs Wells, formerly of the Cornell Lab of Ornithology, is a senior director at the Natural Resources Council of Maine, a nonprofit membership organization working statewide to protect the nature of Maine. Both are widely published natural history writers and are the authors of the book, “Maine’s Favorite Birds” and “Birds of Aruba, Bonaire, and Curaçao: A Site and Field Guide” from Cornell Press.