Years ago I tried looking for Baird's sparrow in Cass County. I knew this sought-after songbird was a grassland specialist and, well, there's grass in Cass County isn't there? Little did I know how ridiculous this errant quest was. A friend of mine gently but surely led me to realize I was wasting my time. The bird just won't be here. I was confusing habitat with range.
Many years have passed and I've since come to fully appreciate one overarching characteristic of life in general and of species in particular. That is, it's all about habitat. Here's a quickie definition of habitat from the American Heritage Dictionary: The area or environment where an organism or ecological community normally lives or occurs.
In mid-June I took a photograph of a beetle I didn't recognize and sent it to one of my entomologist friends. Apart from identifying the insect (six-spotted tiger beetle, Cicindela sexguttata), Patrick Beauzay added, "Ours like riparian/moist woods with dark soil." You see, even among the bugs certain living conditions - or habitat requirements - must be met.
Some of my relatives reside in Oregon and take to salmon fishing with gusto. They would tell you a delicate balance of conditions are required of a stream in order for it to be productive or even attractive to salmon species. Consider this short list of water characteristics: stream flows, water temperatures, turbidity (cloudiness), sediment amounts, available cover and water chemistry. All play a critical role in the success or failure of salmon species within any given stream system. It's all about habitat.
In the case of the Baird's sparrow mentioned above yes, Cass County is easily considered within the broad geographical range of Baird's sparrow but the specific habitat needs demanded by this species are utterly absent here. It's nearly a pure native mixed-grass prairie specialist with little wiggle room, something missing in Cass County. Cornell University's account of Baird's sparrow says, "...generally cultivated land is far inferior habitat relative to true prairie."
In a similar fashion, ferruginous hawks are absent from Cass County. References point to rolling grassland or steppes as its preferred habitat. Whatever it is, it is missing locally as one must travel west to at least Stutsman County before encountering this large eagle-like hawk.
In general a habitat is based upon its vegetative cover (like food chains, it all starts with plants) which is driven by climate, soil type, elevation, etc. This certain array of plant life will, in turn, support a certain mix of vertebrates and invertebrates all trying to make a go at life. And it can vary from year to year.
Back in the late 80s when local climatological conditions were very dry, the mix of birds one would encounter was somewhat different. Immersed for nearly 20 years in a wet cycle, our plant life has changed noticeably and it's reflected in the changing roster of bird species present today.
So tied are species to habitat requirements that a reasonably informed person can actually take a look at a piece of woods or prairie and predict with reasonably good accuracy the bird species found within it. I'm confident various experts could do the same thing with amphibians or insects or any other definable group of organisms. Again, it's all about habitat.
Even within habitats we can further divide areas into smaller parcels called microhabitats. For example, within a typical nearby forested area we might find ovenbirds plodding around on shaded ground in heavy cover and never getting very high in the forest canopy. Above them cedar waxwings will quite often build nests tens of feet high on branches and will have little or nothing to do with the low areas occupied by ovenbirds. Each species' requirement is fulfilled by its own particular niche, or microhabitat, within the larger ecological zone.
With fall migration underway it's intriguing to think what may appear on any given day. Migration tends to ease the strict habitat requirements of most species while not ignoring them entirely. A western grebe, for instance, will not suddenly abandon its watery life for one in the woods. Still, I doubt I'll ever find a Baird's sparrow in Cass County; there's just not enough quality native prairie present to be attractive to them. Redundant as it is, it's all about habitat.