The sighting of the American white pelican on the Penobscot River in September, which I wrote about in last week’s column, has captured a lot of attention. Since so many people have expressed interest in the bird, this week’s column will explore its life history in more detail.

The white pelican is one of two species of pelican – the other is the brown – that breeds in the United States. Although there are structural similarities between the two, their behaviors and breeding ranges are quite different.

The brown pelican, a saltwater bird, breeds in the southern United States and northern South America; it is in these latitudes where most people usually expect to find any pelican.

This is where the white pelican diverges. It may winter in southern climes, but its prime breeding range extends from Canada down through the Western and Central United States.

It seems incongruous to imagine a bird like the pelican at home in states like Wyoming, Colorado, or Montana -much less in Alberta or Ontario. But make a home there it does, nesting in colonies on islands in freshwater lakes.

Each bird employs vastly different strategies to secure food. The brown pelican dives steeply into the sea from a height of 65 feet to capture prey. The white pelican forages in shallow water of marshes or along lakes and rivers. In this case, plunging from a great height into the water could well prove to be deadly, so the white pelican has developed a unique method of gathering food.

A group of several pelicans may line up and begin a coordinated drive of fish into shallow water. With movements that are perfectly choreographed, they simultaneously dip their bills into the water and scoop up pouchfuls of the corralled fish.

Other birds may take advantage of this strategy. Judy Markowsky of the Fields Pond Nature Center has observed cormorants following along and egrets wading into the watery rodeo to grab their share of the bounty.

This foraging behavior may be just a survival technique for the white pelican, but for us it is a beautiful natural ballet.

Both the brown pelican and the white pelican have faced different environmental pressures. Brown pelican populations crashed in the 1960s and 1970s due to contamination by DDT and dieldrin.

These pesticides caused eggshell thinning, as they have in other birds, and very few young were born. Numbers fell so low that the bird was placed on the endangered species list in 1973; populations have since recovered in many areas.

White pelicans have not seemed to suffer from pesticide poisoning to the same extent. According to Roger M. Evans and Fritz L. Knopf in the Birds of North America, their greatest threats have been, and continue to be, destruction of habitat and human intrusion at nesting colonies. Evans and Knopf have observed they are very sensitive to disturbance, and will desert their nests if this occurs early in the incubation phase.

At the very least, they will fly up when people approach; this leaves eggs and young extremely vulnerable to extreme temperatures and predation by gulls.

Such is the story behind the sighting of the white pelican in Maine last month. Hopefully, it will lead to a greater appreciation for them and other birds, as well as foster efforts for their protection.

Chris Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com