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This year, 2016, marks the centennial of the first Migratory Bird Treaty, which the United States signed with Great Britain on behalf of Canada. That treaty and the three that followed — with Japan, Russia and Mexico — form the cornerstones of our efforts to conserve migratory birds, like the Cassin’s Sparrow.

Arvind Panjabi of the Bird Conservancy of the Rockies says Cassin’s Sparrow is awfully hard to recognize.

“It really has almost no distinguishing features that really single it out and make it recognizable. Even for experienced birders, when they look at this bird, it’s almost identified by a process of elimination. If it can’t be one thing or another because it lacks those features, well, maybe it’s a Cassin’s Sparrow.”

While not well understood, Cassin’s Sparrow does limit itself to a type of habitat.

“They almost always are in grasslands that have some shrubs.”

Cassin’s Sparrow flies north into Great Plains states, into arid grasslands, to breed. But since perches are few and far between, Cassin’s Sparrow, like the Lark Bunting, darts up into the sky singing for a mate. The male Cassin’s Sparrow flies straight up, then floats downward on fixed wings, singing the entire time. He’s hunting for a mate, yes, but he’s also marking his territory. It’s called “skylarking.” Once the male has found a mate, and the pair have produced chicks. . . once their parenting duties are finished, it’s back to Mexico to winter.

“Like these other grassland birds from the same region, it winters in the Chihuahuan desert of Mexico primarily.”

We say they go there to winter, they actually return as early as July.

“July is when the rains come to the Chihuahuan desert, so things actually start cooling down there in July, and July and August can be a lot more cool and wet down there than what we see in the Great Plains up north. They get the monsoonal flow starting in mid-July, so that’s when the grasslands really start greening up in Mexico. They’re taking advantage of the grasslands in the best times here in May, June and July, but then by the end of July, they’re already showing up on the wintering grounds.”

As is the case with the Lark Bunting and so many species of grassland birds, Cassin’s Sparrow populations are declining.

“We don’t have a good handle on why it’s declining. It’s lost some habitat in its breeding range in the southern Great Plains. That’s almost certain with the expansion of cropland agriculture. In the winter, it’s facing the same kind of threats. Those grasslands are being converted to cropland in northern Mexico.”

The Chihuahuan Desert is being converted to cropland at an alarming rate.

“We see that the grasslands could be gone by 2025. It’s changing that fast. This is a relatively new phenomenon we’re seeing in Mexico, but speaks more to how rapidly the population could decline in the future, given what’s happening on the wintering grounds there.”

Arvind has said the population decline might be due to loss of grassland habitat on the Chihuahuan Desert in Mexico where the bird winters. That challenge is out of our control, but I asked Arvind if there’s anything we can do, on our land, to help this bird.

“Keep ranchland and ranching, because having an economic use of the land that’s compatible in most ways with these birds is essential. Just by maintaining your ranchlands, you’re helping one species or another.”

Playa Country, which ended in late 2016, was a weekly show that featured conservation and wildlife experts — as well as farmers, ranchers and land managers — talking about conservation practices that improve wildlife habitat and landowners’ bottom-line. Our thanks to Cornell Lab of Ornithology’s Macaulay Library, in Ithaca New York, for the featured bird song.