Bird Watcher's General Store

A Morph Color Phase Doesn't Change the Species
11/07/08

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Dear Bird Folks,

I have a question. It seems if two warblers look basically the same, except one has a freckle in a different location than the other, they are given different names and are considered to be two different species. Yet, there are some Great Blue Herons that have coloring that is unlike the normal heron color, but they are called "morphs" and not a different species. Why is that? What is a morph anyway? -Pat, Birmingham, AL.

I know what you mean, Pat,

I totally understand what you mean about birds that appear to be identical, yet are given different names. If you think warblers are tough, check out the sparrows. I swear they use the same illustration over and over and over, but claim each picture is a different bird. They say that North America has fifty different species of sparrows. No way. There are maybe four different sparrows, five tops. The rest are repeats with made up names, just to fatten up the books and to drive us nuts.

A few weeks ago we wrote about albino birds. These are birds with serious genetic issues that caused them to be white, or mostly white. I don't mean any disrespect to any albinos who may be reading this, but albinism is not the norm and is a fairly rare event. A morph, or color phase, happens when birds of the same species regularly develop more than one plumage color. The morph plumage could be any color: white, red, blue, gray, brown, etc. One of the word's most common birds comes in a whole assortment of colors, yet I'd be willing to bet most people haven't noticed. Want to guess what that bird is? I've already given some hints. It's common, it's found all over the world, and sometimes no two of these birds look the same. Got it? Okay, here's one more hint. It begins with "p" and rhymes with "igeon." Now do you have it?

The good old Rock Pigeon, found in cities everywhere, is the same bird worldwide, yet it comes in a variety of colors. Here's more trivia for you. Birds that have many plumages are called "polymorphic." Also, birds that have many plumages and many cheap suits are called "polymorphic-polyester." Fortunately those species became extinct in 1977.

A few birds that aren't as creative as pigeons may come in only two color morphs. These birds are called "dimorphic,"at least that's what I'm calling them. The Great Blue Heron is a dimorphic bird. There is the less common white form, which is typically found around the keys of Florida. It's a real blue heron, except its feathers are white. The Snow Goose is another one of these crazy dimorphic birds, but it took scientists quite a while to figure it out. They used to think there was a white goose called a "Snow Goose," and a darker bird that they called a "Blue Goose." Two birds, two colors, two species, two names. Then in 1983 somebody asked the birds for their IDs, and probably some DNA, too. It was discovered that the geese weren't two different species of birds after all, but one species with two different plumages.

This brings us back to your question. If a "freckle" can separate two warbler species, why shouldn't two differently colored geese or herons be considered two different species? It has to do with breeding compatibility, and breeding compatibility has nothing to do with looks, thank goodness. Birds typically only breed with birds of the same species, no matter how similar they appear. If a Blue Goose regularly breeds with a Snow Goose, and produces healthy and fertile offspring, then they are same species. That's just the way it is.

A few weeks back I received a related, but odd question from a guy named Jon, who is from Eastham, MA. Jon was bothered by the fact that (these are his words, not mine) black labs and French poodles can easily hook-up and produce "labradoodles." Yet, hummingbirds and ostriches never get together to produce "humriches." (Whoa! That's weird even by my standards.)

Strange as it sounds, Jon's question may help answer your question, Pat. Domestic dogs, from the biggest Great Dane to the ugliest pug, are basically, believe it or not, the same species. That is why they have no problem mating with each other. We have created different breeds of dogs, but not different species. Wild birds, on the other hand, are all different species and therefore don't interbreed. A cardinal won't mate with an oriole, a chickadee won't mate with a sparrow, and a hummingbird definitely won't mate with an ostrich, no matter how much it's been drinking. Sorry, Jon, they'll be no humriches.

Occasionally, closely related birds that can't find appropriate mates, probably due to population decline, will interbreed. This may lead to some rare hybrids, but most often the resulting offspring are genetically inferior or sterile and are quickly out of the gene pool.

I know this morph thing is a tough one to wrap your head around, Pat, but just keep pigeons in mind. A city pigeon is still a city pigeon no matter what color it is or how many freckles it has. I hope that make things a bit clearer. Just don't make me try to explain labradoodles. I have no idea what that's about.



Artwork by Catherine Clark


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