The lake is calm and peaceful this morning. Some 37 Canada geese are resting on the sandbar. Among them, a few double-crested cormorants jostle for room. A light breeze is rippling the surface of the lake, and the path of Bear Creek can be seen by the dark streak running across the ripples like a smooth black ribbon.

The willows along the boardwalk, which were pruned back this spring, are beginning to grow back again, but the pruning has served its purpose. The red-winged blackbirds did not nest in them this year, for they were too short, and therefore have not been dive-bombing every walker and jogger who comes along the walk.

Swallows have been darting back and forth as I sit here. They have been catching insects to feed themselves and their young. They are mostly cliff swallows, but I did see one barn swallow in the group. A few young of the year have already left their nests and are sitting on the utility line that runs along the south side of the lake.

Soon this line will be packed with immature swallows.

Some will learn quickly and fly out to catch their own food as their parents do, but others seem less sure of themselves and clutch the wire tightly while calling to their parents, who will continue to bring them food for some time.

Many people refer to these birds just as swallows or a swallow, as if they were all the same kind. They are not. There are six species of swallows in Colorado, as well as several species of swifts. One can expect to see most of these fairly regularly in the right habitat.

One of the common species is the tree swallow, which arrives here often as early as late March and leaves by early September. All swallows are insect eaters, and their arrival depends upon the weather and the availability of insects. The tree swallows can, when necessary, survive by eating a few berries. Tree swallows nest in cavities in dead trees that are almost always near water or standing in water.

The violet-green swallows are quite similar to the tree swallows in that they both are dark on top and white beneath. However, the violet-green swallow is a brighter white, which comes up on the side of the face and rump, and instead of being the plain dark blue of the tree swallow, their backs are touched with green and violet iridescence. They too nest in cavities but do not need to be as close to water. They therefore may nest in your birdhouse.

Barn swallows nest in barns or other outbuildings; their nests are a flat, open cup made from mud that is stuck to the rough wall or placed in the building.

They are the only swallows that we have which have a deeply forked tail.

The cliff swallow is somewhat like barn swallow since they both have chestnut color as well as dark blue and white. That chestnut, however, is in different places. The adult cliff swallow has a white or cream-colored forehead just above and behind the beak, while the barn swallow has a chestnut-colored forehead. The barn swallow has a dark back and swallow tails, and the cliff swallow has a square tail and buff rump patch. Cliff swallows nest in large colonies; they build their nests of mud also, but they are gourd-shaped and clustered together beneath a protruding rock on a cliff wall or beneath the eaves of a house, barn or other building.

Everyone is fascinated by the swift, graceful flight of swallows and their incredible speed. If you are lucky enough to have a violet-green swallow nest in one of your birdhouses, you can see their entrance into the box. They approach at seemingly full speed, and you think they will crash against the back wall of the nest. But somehow they stop, feed the young, and then exit head-first.

Cliff swallows used to nest on cliffs but now seem to prefer nesting under man’s eves and bridges. Unfortunately, those that nest under bridges frequently lose their young when they leave the nest and are not capable of swift enough flight to avoid oncoming cars. Sometimes the kill is in the hundreds and may cause accidents because the highway becomes slippery.

There are two other swallows commonly seen in Colorado, but they are brown and white, not blue and white. They are the bank and rough-winged swallows. Although they are seen statewide, they are more common on the plains, where there are dirt banks along the rivers in which they can dig a nesting hole. Some of the young blue-backed swallows are brownish before they molt into adult plumage.

You may see gatherings of swallows along roadside wires. They are a good place to study swallows because the birds are sitting still. It is very difficult to see the details you need for identification when they are on the wing.