Habitats and Niches







Western Meadowlark, Sturnella neglecta

From the old French, niche originally meant a bird’s nest or a recess in a wall. Today niche indicates a place or position for someone or something, or a specialized market. But since at least early in the 20th century the word began to be used in an ecological sense. Joseph Grinnell, a pioneering ecologist and zoologist, published a paper in 1917, The niche relationships of the California Thrasher, and the term stuck.

Each species in an ecosystem occupies an ecological niche, defined as all of its relationships with the living and non-living portions of its environment; the niche is what the bird needs to have and do to survive. The niche includes the range of variables the bird has to deal with, such as climate, food, competitors, predators, and vegetation structure. Another way to define a niche (pronounced “neesh” or “nitch”) is the specific role a bird has in its community. Some birds have very wide niches like jays and crows and House Sparrows that are ecumenical in their food tastes and nesting sites. Other birds like hummingbirds, osprey, shorebirds, and pelicans have specific needs and thus narrow niches.

Grinnell was a potent influence in moving ornithology from a collecting and cataloging venture to one that examined reasons responsible for birds’ distributions. In 1904 he accurately stated that the range of the Chestnut-backed Chickadee is due to “atmospheric humidity, with associated floral conditions. For this habitat coincides quite accurately with the narrow coastal belt of excessive cloudy weather and rainfall.”  A bird’s habitat is the physical place it occupies in an ecosystem. Thus, the niche is a bird’s job in an ecosystem and the habitat is the place of employment, or more simply, home. In a coniferous forest, a warbler might prefer the higher elevations of trees while thrushes spend their time on the ground. Spotted Sandpipers prance on the edge of a creek that meanders along the forest edge while kingfishers perch surreptitiously overhead. Narrow-winged Sharp-shinned Hawks fly through the forest while the broad-winged Red-tailed Hawk soars overhead.

            Because each species has its own narrowly defined niche, multiple species are able to exist in the same physical location. Think again of a human community and its retail businesses like a hardware store adjacent to a candy shop. They can coexist because they are in separate niches. Add a convenience store and a plumbing supply shop. Now there is overlap because the hardware store and plumber might both sell faucets and the convenience and candy stores could both proffer gummy bears. Both survive if there are enough resources (in this case, customers). So woodpeckers, warblers, and sparrows coexist well as they have fairly different niches, but what happens if more birds move in? Add creepers and nuthatches and vireos and now how will things work? Can everyone survive?

            A population of birds of the same species has the potential to utilize a variety foraging sites, roosting spots, and nesting locations. But typically there are many species in the same habitat and niches overlap but not too much because resources are finite. A Russian biologist, G.F. Gause, observed populations of two different species of protozoa feeding on yeast and noted that the protozoans in single species cultures reproduced quickly but when the two species were mixed one grew much slower than the other. From these and other observations Gause developed the “competitive exclusion principle”: no two organisms can occupy the same niche, i.e. they cannot coexist if they have essentially the same requirements. Two or more bird species in the same environment must have different niches to survive. How different the birds have to be depends upon the resources of the environment. As we shall see, even seemingly subtle differences can allow coexistence.

            One summer afternoon I was walking along a small river and came upon an American Dipper. Dippers “fly” underwater in pursuit of insect larvae. I thought, what a niche, no competitors. No other songbirds feed anything like that. Oops. Trout and other fish do.  So although we are only considering avian niches here, it’s important to keep in mind the other organisms in the ecosystem as well

From Dr. Seuss:

And Nuh is the letter I use to spell Nutches
Who live in small caves, known as Nitches, for hutches.
These Nutches have troubles, the biggest of which is
The fact there are many more Nutches than Nitches.
Each Nutch in a Nitch knows that some other Nutch
Would like to move into his Nitch very much.
So each Nutch in a Nitch has to watch that small Nitch
Or Nutches who haven’t got Nitches will snitch.


Dr. Seuss, in On Beyond Zebra,