What is there to see and hear this time of year? Chorus frogs emerge from winter chambers to turn quiet ponds into opera houses. Spotted fawns step quietly after their mothers. Lark buntings spiral up in the prairie sky. Mating snakes lie entwined in a tangle of serpentine bodies. Fox kits pounce and tumble, attacking bones, scraps of fur, and each other. Mountain goat kids gambol and play. . . like kids. Prairie dog young sit atop burrows like a class of third-graders. Cliff swallows make endless trips from mudhole to overhang, forming pottery nests with bits of mud carried in their bills.

The activity is evident all around us. Peek in your hanging plants and you may find a house finch nest. A city park with its urban forest attracts all kinds of animal families, from the usual fox squirrels and crows to black-crowned night-herons (check out Denver's City Park), Mississippi kites (Lamar's Willow Creek Park) and beavers (along the rivers at Confluence Park in Delta).

That icon of the North American spring, the robin, brings the whole process, of nest-building and rearing close to us. Living in our backyards, robins let us peek into their lives, showing us every step of the homemaking process. The female robin weaves her cup nest of twigs and grass. She sets her home in a fork of tree branches, gluing the plant fibers together with mud. Bobbing down, she presses her breast into the cup to shape it. Finally she lines the cup with soft grasses, a gentle die for her eggs. Then she lays her clutch of eggs - robin's egg blue, of course - and incubates them dutifully. As anyone knows who has watched a nest of robin hatchlings outside their bedroom window, baby birds are noisy, fascinating, and able to get their parents dancing with their plaintive cheeps. Finally the big babies leave the nest (fledge), but remain dependent on their parents. Songbird young are the size of the adult by the time they fledge. But they're not yet ready to be grownups. Throughout summer you can tell fledged young from adults by their begging behavior–feed me, mama!

Hummingbirds build tiny nests the size of Japanese sake cups, wedged in the fork of a branch. They line their nests with spider silk-satin sheets for the crib. But not all parents make a soft and fancy nest for their young. Birds whose young are able to move around and fend for themselves soon after hatching—precocial, biologists call this—have less need for a cozy nest. Killdeer scrape together a few pebbles or may lay their eggs on a bare patch of sand, or atop a gravel roof. Kestrels, though their young are more dependent than killdeer, use cavities but lay their eggs on the bare surface.

With vigilance and a good deal of luck you may spot the round face of a screech-owl (check out your local park) or a bandit-masked raccoon peering from a hole in a tree. Mammals are not as dependent on holes in trees as are the many cavity-nesting birds, which include bluebirds, chickadees, house sparrows, nuthatches, tree swallows, even wood ducks. Most cavity-nesters aren't capable of excavating their holes and depend on those premier tree engineers - woodpeckers - making cavity-nesting species very vulnerable to declines in woodpecker populations.

Some animals return year after year to reuse old nests. It you watch such nests over several seasons, you can see them grow. One enormous bald eagle nest, in use and added to for more than 34 years, measured eight-and-a-half feet across and 12 feet high. It weighed about two tons and finally collapsed the tree which held it. Bald eagles have nested at Barr Lake State Park near Brighton since 1986, though they have had to rebuild when their nest was lost to storms and a fallen tree. More familiar are the grass and stick nests of songbirds, built each spring, blown down in fall, and carried home by kids to take to show-and-tell.

The natural world is dynamic, and we see that when we're able to watch an animal family through a season. By late January or early February the female great horned- owl is sitting on her big nest, often the former home of a great blue heron or red-tailed hawk. As the snows of late winter fall upon her back, she stays steadfast upon her eggs, fed by her mate. Finally the owlets hatch, but still her job isn't done and she patiently broods her downy babies, sitting higher and higher on the nest as the owlets grow. Even when they fledge, the babies still depend on their parents. You may, see the owlets clustered together on a branch, several pairs of enormous eyes peering down at you as they wait for their parents to bring them, dinner.

Birds aren't the only animals that make use of nests. Rodents are great nest-builders-ask anyone who's had mice invade their basement. A weekend in the mountains with your car parked under the pines is enough time for deer mice to construct a home in your glove box from those extra fast food napkins you keep there. Among all the specialized rooms in a-prairie dog burrow, the birthing chamber is a place reserved for babies like the nursery in a human home. Messy clumps of leaves high in city trees are the winter shelters and summer nurseries of fox squirrels. Woodrats build marvelous nests, collections of sticks, leaves, wire, cloth or anything that captures the animal's interest. Woodrats earned their nickname, packrat, because of their attraction to shiny objects. These rodents, not much bigger than large mice, carry home all sorts of interesting things. During the California Gold Rush, prospectors suddenly got the idea a wealth of gold nuggets might be found in woodrat nests, and countless packrats had their nests torn apart. Look for woodrat nests in canyons, forests and around old mining claims throughout western and southern Colorado.

Don't expect to see activity at a nest year-round. Most nests are a place to rear young, not live in. But other signs of animal habitation are everywhere. Mysterious mounds of loose dirt are the only evidence a pocket gopher leaves of its extensive burrowings beneath the ground. Oval areas of matted-down grass can indicate a spot where deer have bedded down. Elk wander the whole mountainside but they return to favorite areas to rest, often sheltered by a canopy of tree limbs or shrubs. They also use traditional calving, grounds where the cows feel safe giving birth. Black bears build day beds, soft collections of grass, twigs and leaves in a hidden spot where they can nap safely. Of course the bear's winter home is its hibernation den, which might be a cave or rock shelter a cavity beneath a fallen log, or just a burrowed spot within a pile of leaves.

Bats are one seldom-seen animal group whose family and home you can bring to you, with a bat box. Common species like big and little brown bats raise their young in communal nurseries. You can watch the adults come and go and occasionally peek in for a glimpse of the females and their young clustered together—all hanging upside down, of course. Bats seem happy to move into properly built and positioned bat boxes, though it may take a few seasons. Set your bat house on the south or east side of a house or tree where it gets at least four hours of morning sunshine. Place it at least 10 feet off the ground so predators can't get at the residents.

From the time you notice nest-building or denning behavior until you actually see babies varies by species. Songbirds incubate their eggs a relatively short time. About two weeks after the parents finish the nest and lay eggs you can expect to hear the hungry peeping of nestlings. Though great horned owls are on their eggs by February, don't expect to see owlets out of the nest until June. Prairie dog pups are born in March and by mid-April begin to make their appearance above-ground. Coyotes and foxes begin excavating dens in the ground, usually beneath the cover of shrubs, rocks or fallen trees, in March. Look for those fox and coyote young to emerge sometime in April and May.

Now that you're looking, you may find a curious structure but not know whose home it is. Watch and wait—careful not to disturb the occupants—until someone arrives or emerges. You just might be surprised by who pops out.

Next: Watching Young Animals

(The information contained in this issue of Colorado's Wildlife Company was accurate at the time of original publication. Situations and circumstances described, staff positions, contact information, and dates of some events may have changed in the interim. Present knowledge and understanding of biological and behavioral facts and information may also be different, now, than presented here.)