Birds are the next class of organisms in our tour of vertebrates. Officially, the class “birds” is called “Aves,” again this is a Latin word. On the outside, birds look much different from the class reptilia, however birds are believed to have evolved from an extinct order of reptiles. Since we have spend a fair amount of time on reptiles, birds should be easy. So in some ways, birds, like modern reptiles are the descendants of dinosaurs. How than are birds and reptiles similar? The easiest way to understand this is to think of how a small dinosaur would need to evolve to gain the ability to fly. Let’s discuss this….
You guys came up with most of the important adaptations that a dinosaur would need to fly. However lets refine these ideas a bit and discuss the characteristics that all birds have.All birds have feathers, most birds use feathers for flight, however some birds are now flightless. These flightless birds have found a niche in an environment that makes flying not necessaryAll birds are endothermic. Unlike reptiles and the other vertebrates we have studied, birds regulate their internal body temperature. Endothermy is commonly known as being “warm-blooded.” Reptiles body temperature changes with the air temperature. Birds try to keep their body at a constant temperature.Birds have hollow bones that allow for lighter weigh bodiesBirds have a 4-chambered heart. Because moving wings takes a lot of energy, birds must circulate oxygen quickly through out their body. A 4-chambered heart allows an animal to have much higher oxygen capacityAmniotic Eggs. Like reptiles, birds have external embryonic development using the amniotic egg. Forelimbs have evolved into wings. Birds don’t have arms, they have wingsBirds are toothless. Hard birds beaks have evolved to function similarly to teeth
The most important bird adaptation is the modification of reptilian scales into feathers. YES…FEATHERS ARE SIMIPLY MODIFIED SCALES. Feathers are the perfect flying device. They are lightweight, strong and still provide enough lift for flight. Not only are feathers used for flight, but they also provide warmth allowing birds to inhabit much colder environment than their reptilian cousins. We’ll use the Smartboard to label the parts of the feather using the diagram on the slide. As the diagram shows…feathers are more connected than they appear. There are 3 main types of feathers:Down feathers which are the “undercoat” for the bird. Down feathers provide incredible amounts of warmth for the birds. People use goose down for jackets, bedding, sleeping bags and much more.Contour feathers are on the outside of the bird and streamline the bird reducing drag during flight. Think of contour feathers like the outside of a race car…the body of a race car needs to be sleek and smooth. Contour feather do this for the bird.Flight feathers are found on the wings and tail and are used by the bird for controlling itself during flight. Because balance is so important during flight, birds always molt their flight feathers in pairs so they maintain wing and tail balance
Because birds don’t have teeth or forelimbs, their beaks are used for many different functions. Over the course of many generations, bird beaks have evolved with the available food in an environment. Charles Darwin actually used the beak shapes different types of finches to help develop his theory of natural selection. Lets discuss and label each type of beak….
As we discussed earlier, reptiles and birds are closely related. The feet of birds are one area that really shows this. Birds have reptile like scales on their feet. This was one of the first ways that early scientists explained the evolution of vertebrates. Why do birds have such different feet? Because the forelimbs of birds have evolved into wings, the hind limbs are used for many tasks that other animals would use their forelimbs for. Let’s discuss and label each type of bird foot.
There are over 20 different orders of birds, but we are going to only discuss 4 today. How might birds be grouped into orders? You guys did a great job of coming up with the ways scientists group birds. Generally speaking, birds are grouped:By beak typeBy foot typeBy plumageBy bone structureBy muscle arrangement
Birds of prey are divided into two classes. The first class is daytime birds of prey called the Falcomiformes and include birds such as eagles, falcons, hawks, and vultures. They are typically the largest and fastest of all birds. The fastest bird is the peregrine falcon, which can dive at speeds over 200 mph. Let’s watch this video clip of peregrine falcons (click on the hyperlink).The second class is the nighttime birds of prey called the strigiformes and make up all the owls. The owl’s unique facial features help in navigation and finding prey at night. Let’s watch this video clip of a snow owl (click on the hyperlink).
Shorebirds make up the class called: charadriformes. These birds include the ever popular seagull and sandpiper. These birds have wading legs and scavenge for food along waterfront areas or in the case of seagulls even landfills! Most people that live close to the ocean consider seagulls “rats with wings.” For the most part we would agree that birds are not the smartest of animals, but I had to show this video clip of a very enterprising seagull (click on the hyperlink).
There are several groups of flightless birds that we could discuss, but it’s hard to argue with the incredible beauty of the penguin. Penguins belong in the class: sphenisciformes. They are found in Arctic or Antarctic waters. They have lost their ability to fly in the air, but have gained the ability to “fly’ underwater. If you have ever been to the zoo and seen penguins swim, you will agree that they truly fly in water. Their feathers are modified for cold temperatures and water. Let’s watch this video clip of king penguins from the BBC and our friend David Attenborough (click on the hyperlink).