As May arrives in the South Platte Valley, significant changes are underway. Wintering waterfowl have left the river, dispersing to northern breeding grounds, while summer residents, including cormorants, white pelicans, waders and songbirds are arriving from the south. At the same time, melting of the mountain snowpack is beginning to peak and the river's flow increases dramatically.
As a consequence, much of the "action" shifts from the river to the woodlands, lakes, fields and wetlands that cloak the valley floodplain. A rapid, deep river does not appeal to many water birds and nesting species, such as Canada geese, mallards, cormorants, great blue herons and black-crowned night herons, spend most of their time on or along the calmer waters of adjacent lakes and marshlands. Permanent woodland residents, such as flickers, magpies and great horned owls, are now joined by a host of insectivores, including yellow warblers, western wood pewees, house wrens, northern orioles and blue-gray gnatcatchers. Even the beaver and muskrats seem to avoid the turbulent river and spend most of their time at the ponds and lakes.
Exceptions, of course, occur and, this year, a large cliff swallow colony has been established under the Mineral Avenue bridge, in Littleton; clouds of these active birds rise and fall above the river as they hunt for insects and return to their mud nests to feed their young. By July, water levels along the South Platte begin to fall, sandbars reappear and many of the water birds return to the river; until then, there is much to observe at the other floodplain habitats.
