The Anna’s Hummingbird has undergone a major range expansion since the 1930s. And that’s largely due to humans. One study found that Anna’s Hummingbirds tend to colonize new locations, even cold ones, based on housing density — that is, how many people live there — and the availability of…

Some early sailors, visiting remote Pacific islands, surely feared that the ungodly wailing on shore meant they had been tricked to the gates of Hell itself. In truth, they stood among courting pairs of seabirds called Wedge-tailed Shearwaters. These birds nest on islands in the tropical…

The swallows that make mud nests in spring and catch flying insects all summer are now far south in Mexico, and Central and South America. It's only as recently as the end of the nineteenth century that ornithologists agreed that swallows, including this Cliff Swallow, migrate. Many…

Pinyon Jays take their name from pinyon pines. Extracting the seeds from cones, the jays fill their throats. Then they fly to a caching site, sometimes miles away, to push each seed into the leaf litter. Collectively, they cache millions of seeds, some of which sprout before they can be…

During the last ice age, part of the ice sheet covering what is now western Canada advanced far enough into Idaho to block a major waterway, now called the Clark Fork River. The ice dam backed up the river, creating a gigantic lake in (what is now) Montana. Every so often, the weight of…

High in the mountains, a Clark's Nutcracker buries a cache of whitebark pine seeds. This will be nearly its sole source of food until the next summer. But some of those cached seeds will germinate, spawning a small grove of pines. Whitebark pines are one of more than 20 species of pines…

In many birds, plumage is often the easiest way to tell males from females. But in raptors, size is often the best indicator of sex. In many bird and mammal species, males are larger than females. But in birds of prey, including Ospreys, hawks, falcons and eagles, the rule is reversed. It…

There are more than two dozen species of gulls living in North America. Some people might dismiss them as just “seagulls.” But not the people of Port Orchard, a small town on Washington State’s Puget Sound. Each year, hundreds of people gather at the town’s waterfront in late May for the…

As an old story from Germany goes, workers building the world’s tallest church were preparing to install an immensely long beam, but they couldn’t get it through the city gate. Preparing to dismantle the city wall to clear a path to the construction site, workers saw a House Sparrow carry…

It’s October in Yosemite. Acorn Woodpeckers, Clark’s Nutcrackers, Red-breasted Nuthatches, and Mountain Chickadees like this one know it’s time to stock the larder! For us, there’s still time to enjoy a hike b efore the harshness of winter. As John Muir put it: “Climb the mountains and get…