What's mind-boggling in the above chart is represented by the big black slice composing more than half of the pie. But before we get into that black slice, let's get oriented. You may want to review the information on our Pigeon-Holing our Discoveries page.
On that page you see that birds are, of course, animals, and since they are animals with backbones, they belong to the phylum Chordata. Then the phylum Chordata is divided into various classes, and one of those classes is the bird class (other classes are the reptile class, the bony-fish class, and the mammal class). Now, the above pie chart shows that the bird class is divided into about 30 orders, and the big, black slice shows that of those 30 orders, the passerine order has more species in it than all other bird orders combined!
In other words, if you have a typical backyard bird feeder, most of the birds visiting that feeder will probably be passerines -- sometimes also known as perching birds. The main kinds of birds possibly visiting your feeder not belonging to the passerine order are woodpeckers, doves and hummingbirds.
Therefore, right off, knowing a bit about bird classification helps you appreciate woodpeckers, doves and hummingbirds a bit more than otherwise you might. If woodpeckers, doves and hummingbirds are so unlike "regular birds" that they have their own order, then there must be something special about them. With the woodpeckers' chisel-like beaks and strange feet (two toes up front and two behind), and the hummingbirds' slender beaks and weak feet, we know what's peculiar about them. However, what's so special about the dove order, in which pigeons belong? Are pigeons really so unusual?
Well, yes, several things set pigeons apart. Their beaks are strange in that they are short, the hard tip is actually wider than the middle of the beak, and at the base of the upper mandible there's a cere, a waxy-appearing, folded membrane softer than the rest of the bill, and it's in the cere that the slitlike nostrils appear. This strange bill helps make doves and pigeons one of the few kinds of birds that dip their beaks into water and suck up the water as a horse might. Other birds fill their beaks then raise and tilt back their heads to let the water run by gravity down their throats.
So, this is how pigeon-holing our birding finds works. When we realize that members of the bird world are divided into various groupings, we begin wondering what holds these groupings together, and then we discover interesting things that otherwise we might have missed.
As we said, the bird class is divided into about thirty orders, the exact number depending on which specialist you listen to. (Nowadays with genetic sequencing there's a great deal of discussion about this very question, but most of the birding books on the market still use the comfortable old systems, so we'll just stay with them.) What's nice is that the number thirty-odd is such a decent, comfortable, manageable number that our brains can deal with it. If there were a hundred orders, we'd just get confused, and if there were just five, then it would be less fun, because it would mean that there would be less diversity in the bird world.
Actually backyard birders don't have to worry about nearly as many as thirty orders, since representatives of many orders will never appear in our backyards -- no penguins or ostriches, for example. An average walk around a neighborhood including a park might produce sightings of birds representing four or five orders. If we become fairly serious birders seeking out a number of habitats, a good walk may yield species in ten to fifteen orders.
This order business becomes especially relevant when using a field guide to identify birds because nearly all field guides place all the species of the same orders, families, and genera together. Thus all the species of the hawk order are found in one section of the field guide, all the species of the sea gull order are in another, and so on. Once you gain a little experience birding, you'll know at a glance which order your unknown bird belongs to so when you go looking for its illustration in the field guide you can ignore the pages dealing with birds in other orders. In other words, if you have a gull, you won't have to wade through all the hawks, sandpipers, and sparrows.
Orders are divided into families. Knowing at a glance which family a bird belongs to is helpful for exactly the same reason that knowing its order is helpful. Once you have a feeling for bird families, you should take a look on the Web at The University of Michigan's Bird Page, where you can see a much more detailed outline of how birds are related to one another. Click on an order and you'll see a list of bird names in that order. Click on an order or family names and you'll go to a page with even more detailed information. At each level, many names have a camera icon to the left. Click on this icon to see pictures showing what birds of that order, family, genus or species might look like.
It's understandable that beginning naturalists might think that "names and classification" must be the absolute most boring part of birding. However, without understanding this field, our talking and thinking about the vast, varied bird world would have to be kept at a pretty basic level. We wouldn't know what's special, and why. And we wouldn't be able to see how our backyard birds fit into the much broader bird world.