Monday, September 18, 2006

FEATHER MUSCLES POWER FLIGHT

I watched a hawk flying above me. Buffeted by the wind, pulled on by gravity and aerodynamic forces, the hawk maneuvered in the air, a master of flight. With many fine, tiny moves, the bird made micro-changes in the position of its feathers to maintain position and react to the changing dynamics of flight.

I marvel at the meticulous control of flight that birds are capable of, so different from the flight of an airplane, with its fixed wings and featherless metal skin. Not only do birds have powerful flight muscles that power their wings, but each feather is controlled by tiny bunches of muscles in the skin. The feather muscles attach to the follicles, the depressions in the skin that the feathers grow out of.

The feather muscles can raise or depress each feather, twist or rotate it, draw a group of feathers together, and do several of these actions at the same time. They also allow the bird to spread or close its wing feathers. Birds are covered by thousands of feathers (the number varies by species—smaller birds have fewer feathers). It takes even more thousands of muscles, working together, to control the complex network of feathers that covers the body. Control of these muscles is automatic. The bird senses changes in wind and flight dynamics and the muscles react without the bird having to think about it. 

Feather position affects not only flight, but body temperature, behavior displays and communication between birds. It also plays a part in a water bird’s ability to swim, dive or remain buoyant.

Next time you have a chance, look closely at a soaring or gliding bird and notice the fine-tuning of the feathers. It’s a marvel of nature.

Monday, August 14, 2006

BLUEBIRD NEST BOXES A SUCCESS

The bluebirds have flown.

That’s what we discovered this month when we checked our trail of bluebird nest boxes in Las Animas County, west of Trinidad. 

We have ten boxes positioned at the edge of a series of meadows. By April, western bluebirds were paired up and searching for nest sites. By Memorial Day, one box held newly-hatched babies—naked, featherless “pinkies” with stubs for wings, bright yellow beaks and enormous, dark, unopened eyes visible through their transparent skin. Five other boxes held clutches of four or five eggs. Most of the eggs were sky blue, but one set was white with brown streaks.

The blue eggs belonged to our most common tenants—western bluebirds. Bluebirds spend winter in southeastern Colorado, so it is a short commute to their summer nesting grounds. Some bluebirds remain in the area for the winter, though I don’t know if these are the same birds that nest here. Bluebirds incubate their eggs for about 14 days, then brood the young for another 21. Beginning early in the season allows bluebirds to have a second, and sometimes third, brood.

The white and brown eggs belonged to ash-throated flycatchers. They raise one brood a year—this year a nest of four young.

By the end of the summer, 2006 had turned out to be the most successful nesting season since we put up our first boxes in 2000. All 10 of the boxes had nests. We had second broods of bluebirds in two of the boxes. Violet-green swallows, which begin nest-building quite a bit later than bluebirds, took over two other nest boxes after the bluebirds had fledged their young. Between them, the two boxes held seven baby swallows.

We can’t take credit for all these baby birds. We’re just glad to be helpful landlords, and privileged observers.

July 2006

BEGGING BABIES KEEP BIRD PARENTS HOPPING

Have you noticed some odd behavior going on among the birds in your back yard? Have you seen one bird pestering another, following it from branch to branch, landing in front of it, squawking, peeping, opening its beak, vibrating its feathers? The first bird may feed the pest, or move away from it. Given food or not, the pest follows the other bird, carrying on like a nagging spouse.

If you’re thinking this is about romance, think again. It’s about the product of romance—kids.

The pests are young birds that have left the nest (fledged) but aren’t quite ready for independence. They still beg food from their parents, hence the open beak, the vibrating feathers, the squawking. The young may look like grownups—most young songbirds are the size of their parents when they leave the nest, and have the same plumage—but their behavior gives them away. Sound familiar?

If you have children, you’ve likely been the focus of this behavior yourself—at the popcorn stand in a movie theater, driving past the ice cream shop, stopping for fast food. Feed me!

Depending on the species, birds may care for fledged young for days or weeks. Caring for young increases the chances for their survival. But there is a biological cost to the adults. It takes energy to feed extra mouths and the adults are more vulnerable to predation as they pay attention to their dependent babies. And many adults may be preparing to lay another clutch of eggs. It becomes time for the young birds to make it on their own.

I’ve observed this behavior all week among the pygmy nuthatches in my yard. The young peep and vibrate in front of their parents, and are rewarded with an insect or a dab of suet. But the young birds are in a steep learning curve as they discover where and how to find food on their own. Soon the adults will ignore the begging behavior and begin avoiding the youngsters. Then it will be time for the young birds to spread their wings and fly away.

Monday, June  5, 2006

BIRDS AND BIRDSONG THRIVING ON RATON MESA’S VAST GRASSLAND

 The steep hike up the three and a half mile trail was worth it, despite carrying a 40 pound backpack and herding two 2^nd-graders. Stopping to watch birds in the mountain forest wasn’t on the agenda, but I enjoyed listening as I hiked to the bell-like song of a hermit thrush, the nasal yank of a nuthatch, the see see see look at me song of a ruby-crowned kinglet.

We popped out on the top of Raton Mesa and saw a vast grassland spreading into the distance, a prairie at 8800 feet. Oakbrush and ponderosa pine lined the mesa edge like a ribbon of woodlands circling a grassy plate. Mesa means table in Spanish, a perfect name for these flat-topped uplifts that rise 1,000 feet above the surrounding plains of southeastern Colorado. Like sky islands, they offer vast way stations of people-free habitat for migrating birds, and rich nesting areas for those that stop to spend summer.

Our campsite at the edge of the mesa put us in the middle of “edge habitat.” These places where different habitats meet are rich with birds. Western tanagers, startling in their yellow, black and scarlet plumage, haunted the pines. Like pieces of the sky, mountain bluebirds flitted across the tall grass. Green-tailed towhees, chipping sparrows and savannah sparrows sang from the oakbrush. A cloud of crested birds in elegant gray plumage arrived in the evening, adorning a dead tree like Christmas ornaments. Cedar waxwings are a delight to see, and a treat. Whimsical in their habits, they were gone by night. Clark’s nutcrackers and ravens squawked at us. Where the mesa’s sides fall away like the walls of a canyon, white-throated swifts swirled in the airspace and turkey vultures floated dreamily below us. Robins, flickers, yellow-rumped warblers, broad-tailed hummingbirds, mountain chickadees, red-tailed hawks all added to the carnival of color, sound and motion.

The mesa top, protected as a state wildlife area, gave me a sense of what the Front Range was like hundreds of years ago, before the onslaught of great numbers of people. The abundance of birds, their exuberant activity, and the lack of human imprint made me know we were only visitors in this wild place.

Monday, May 8, 2006

LENGTHY LIST OF FEATHERED FRIENDS IN PERIL

 After last month’s column on the Endangered Species Act, several readers asked for more information. Last month, the National Audubon Society issued a four-color booklet, America’s Top Ten Most Endangered Birds. It’s available as a pdf online at www.Audubon.org.

Only two of the 10 birds in the booklet are found in Colorado. The Gunnison’s sage-grouse is a chicken-sized ground bird that inhabits sagebrush habitat. It is about one-third smaller than the typical sage-grouse and until recently was not considered a separate species. Populations have declined because of loss of sagebrush shrublands to development, resource extraction and agriculture. Gunnison’s sage-grouse is not yet listed as an endangered species, though only seven populations remain in isolated areas of southwestern Colorado and southeastern Utah. There are an estimated 3,500 Gunnison’s sage-grouse in Colorado, most of them in the Gunnison Basin.

The piping plover is a pint-sized shorebird that looks like a small, pale killdeer. In Colorado, piping plovers nest on the bare, sandy beaches of several Eastern Plains reservoirs. They are more common along the Eastern Seaboard, the Gulf Coast and northern Great Plains. With the far-reaching development of coastal areas, human activity has taken a huge toll on piping plover nests, eggs and chicks. The plovers’ camouflaged nests are easily destroyed by human feet, pets and vehicles. Only an estimated 6,100 piping plovers remain.

Other threatened and endangered Colorado birds that are not on Audubon’s “most endangered” list include the bald eagle (likely to soon be de-listed), whooping crane, least tern, Mexican spotted owl, southwestern willow flycatcher (a small songbird), plains sharp-tailed grouse, burrowing owl and lesser prairie-chicken. Species classified by the Colorado Division of Wildlife as of “special concern” include: western yellow-billed cuckoo, greater sandhill crane, ferruginous hawk, American peregrine falcon, greater sage-grouse, western snowy plover, mountain plover, long-billed curlew and Columbian sharp-tailed grouse.

NOTE:  May 11 is Endangered Species Day! On that day, think about taking a bird walk, feeding birds in your back yard, and talking with kids and neighbors about why we should care about protecting wildlife from extinction.

Monday, April 10, 2006

KEEP AN EAGLE EYE ON PROTECTION LAWS

Anybody in Colorado seen a bald eagle? Okay, maybe I should ask, anybody in Colorado NOT seen a bald eagle? If you’ve driven along the Colorado River, been around Chatfield Reservoir, visited Barr Lake, been to any of a hundred reservoirs or rivers throughout the state, you’ve probably seen bald eagles. That’s eagles, plural. Those white-headed, fish-eating, prairie dog-hunting, prey-pirating raptors are everywhere. But 30 years ago, it wasn’t so.

In the 1970s, bald eagles were truly on the brink of extinction. We had only one breeding pair in Colorado. In the Lower 48 state, there were only about 400 nesting pairs total. That ain’t many. How shameful it would have been if we Americans had allowed our national symbol to go extinct. But we didn’t. We passed the Endangered Species Act. The Act saved the bald eagle and it’s been a powerful tool for protecting our most vulnerable wildlife and plant species. By 2001, we had 51 nesting pairs of bald eagles in Colorado—in thirty years, 50 times more eagles. That didn’t happen without the help, protection and commitment of the American people.

Right now, there are several bills before Congress that would weaken or even gut this law (our senator, Wayne Allard, is co-sponsoring one of them). They want to weaken requirements to protect species so that recovery efforts and protections are mere tokens that would be mostly voluntary, without enforcement. They want to take away the provision for critical habitat—this means protecting wild places that are essential for a species to survive. Sure, there are probably ways the Endangered Species Act could be improved. But these bills are way too radical. This is not a nature-friendly group of folks we currently have in Congress.

Hey, the wild heritage of our state—whether it’s eagles or elk or columbines—is incredibly important to me. I bet it is to you, too. When you hear about efforts to gut the Endangered Species Act, I hope you’ll speak up and help keep Colorado the wild and wonderful place we all love.