Ornithology and Birding

Ornithology and Birding Around the World


On the Evolution of Birds

Cactus Finch.

Cactus Finch.

The concept of flight has always caused wonderment in the human race, as philosophers devised odd flapping contraptions modeled after birds. But how and why did birds develop flight? Many of us know that birds evolved from reptiles, but for many of us that is the extent of our knowledge. The first bird, Archaeopteryx, was quite reminiscent of dinosaurs, with a toothed beak and clawed, fingered wings. It is believed it evolved feathers to create lift when jumping to catch insects. However, Archaeopteryx was more of a glider; why did flight itself develop? Nobody knows for sure! But what we do know is how birds got there. One part of a birds’ anatomy is the alula, a small patch of feathers on the wing that is often considered unimportant. It is often thought of as being the birds’ thumb, and acts much like the adjustable slats on the leading edge of an airplane’s wings. It allows a bird to control takeoff and landing more easily and also increase lift if necessary. Birds are truly the champions of the air, but evolution has not only granted them flight; it has made birds true celebrities rather than ‘that thing in the yard with a beak and wings.’ You may have heard of Darwin’s finches, a group of birds almost exclusively endemic to the Galapagos Islands. Darwin used these birds to propose the theory of evolution by studying the varied beak forms. Depending on the food available on an island, the finches developed beaks to best suit their diet. For example, finches eating buds developed large, hard beaks, while finches who preferred grubs had a probing beak like those of woodpeckers. Probably the most amazing thing we have learned about evolution through birds was how fast it can occur. In 2006, a study discovered that when the large ground finch began appearing on the Galapagos island, Daphne, the medium ground finch population on the island, which has lived there for thousands of years, evolved a smaller beak to avoid competition – within just two decades! Even more shocking is that the majority of the change occurred within a single generation. The third thing we learn about with this article is that we are learning so much so often. There is still a treasure trove of information about bird evolution just waiting to be dug up, and it is exciting just to think about what it may be.

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Sources:

Evolution: Bird Evolution

Biology Online: Darwin’s Finches and Natural Selection

National Geographic online article

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Bird of the Week: Pileated Woodpecker

Let’s imagine for a moment that you are walking through a mature forest and a male Pileated Woodpecker lands on a dead snag not five meters away. It is truly a glorious bird, over a foot-and-a-half long with a flaming red crest. It gives you a cautious glance, but being the size of a crow and sporting a beak that hammers out wood at 25 pecks a second, it doesn’t have much to fear. As it goes about its feeding business, you begin to note some of its features. The body is almost completely black and the neck is striped black and white, and the contrast between the crest and the rest of the bird is almost unreal. You wonder if there is a female nearby, and your question is instantly answered as a piercing ‘kuk-kuk-kuk’ call rings through the forest. Looking back at the male, you can see the mandibles of the beak are opened slightly by something between them. Before you can get a look at what it is, the bird flies off to a cavity you hadn’t noticed before. A fluffy, crested head peeks out of the nest hole, and the food is transfered to the hungry youngster. As the male flies to another favored feeding area, you have a chance to inspect the snag it left. The holes bored by the powerful beak are noticeably rectangular, and inside those holes you can occasionally see an ant or grub barely missed by the woodpecker. All of a sudden you hear another bird behind you; it is a Red-bellied Woodpecker, another resident of these woods. As you walk away, trying not to disturb it, it flies to the dead tree and begins feeding through the excavations created by the larger woodpecker. You smile as you see another species benefitting from the borings. It is starting to get dark. As you begin to walk back, you hear for one last time the resonant call of the Pileated Woodpecker, as it raises the next generation of a bird that many will enjoy for the years to come.

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Source:

All About Birds – Cornell Lab of Ornithology