The convoy of five cars heads slowly up the mesa through a patchwork of open fields and cedar woodlands. Binoculars around my neck, I sit in the backseat of a well-used Subaru station wagon amid a scattering of stray goldfish crackers and one, apparently unused, diaper.

The driver is Jason Beason, a young father and biologist who works for the Rocky Mountain Bird Observatory, based in Brighton, Colo. He is our leader on this Saturday morning expedition, which was organized by the local Audubon chapter. Our objective: to find and identify as many raptors as possible in this corner of western Colorado.

Jason suddenly pulls off the road and jumps out of the car: "There, " he says, "on top of that irrigation pivot, three sections from the right."

Into view pops a hawk with black-and-white plumage. Jason promised us a rough-legged hawk this morning, and he has delivered. Several pairs have been in the area all winter, he says, drawn to the ideal habitat -- cleared pasture surrounded by a scattering of good fence posts, irrigation pivots and solitary cottonwood trees from which they can launch their hunts for the innumerable mice and voles that thrive in irrigated hayfields. It's a semi-domesticated ecosystem, and it also appeals to birds like the Northern harrier, one of which, minutes later, sweeps low across the same field, flashing its white rump.

In fact, almost all of the birds we see this day thrive on the alterations humans have made to the land. Even the bald eagles -- and we see six by day's end -- fish for exotic trout planted in our reservoirs and feast on the nutritious afterbirths left by calving cows. Would they be here if we were not? Probably, Jason says, but not in the same abundance.

It's refreshing to think that we humans aren't always the villains when it comes to biodiversity, that we can actually create thriving habitat that supports native species. But for every success story, there are several sad tales of loss. In early April, Jason and I drive through a sea of sagebrush, looking for a rare population of Gunnison sage grouse. With our guide, Doug Homan of the Colorado Division of Wildlife, we pass through a closed gate and wind our way on a rutted road toward several grouse breeding grounds – known as leks. We scare up hundreds of elk and mule deer, but the grouse are scarce. Many leks are empty, and it is not until the final stop that we spot five strutting males. They fly off within minutes, apparently disturbed by the presence of our truck.

"We think there have been as many as 250 birds in this area," says Homan, who has kept track of this population for two decades. But the counts have been small this year, and Homan is worried that the population is falling, despite human efforts. Homan says land managers have cleared sagebrush to create more breeding grounds, cut down the juniper and oak trees to reduce perches for grouse-loving raptors, kept eager elk-and deer-antler collectors out of the area during breeding season, and worked with local ranchers to time cattle grazing so as not to disturb nesting hens.

So what's the problem? "I couldn't tell you specifically," Homan says, "but it's human caused. We could be actually be trying to do too much for the birds."

There are wildlife winners and losers in the increasingly human-altered West. Still, in the powerful awakening of a Rocky Mountain spring, I have a hard time being all doom and gloom. My favorite birding spot these days is a place called Fruitgrowers Reservoir, a shallow, algae-filled agricultural impoundment that has become a one-night stand for tens of thousands of migrating sandhill cranes.

One recent morning I watched 3,000 cranes warm their wings and strut and dance as cows and calves cavorted at the water's edge. Then, responding to some subtle cues, the cranes took off. In groups of 30 and 50 and 100, they circled higher and higher above the fields, trumpeting their wild reptilian call across the semi-wild land.

Paul Larmer is a contributor to Writers on the Range, a service of High Country News in Paonia, Colorado, where he is the publisher.