We can start by taking a look at the classification of thebirds for which you will be held responsible on the 3rd midterm.
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As you can see the Class Aves is divided into 2 subclasses andthe more primitive of the 2 is the Subclass Archaeornithes whichaccording to current accepted classifications has only a singleorder. That single order containing only a single genus. And thatsingle genus containing only single species. So clearly we'relooking at a very, very unusual species here which is the animalcalled Archaeopteryx. Which is placed in a single species forwhich an entire subclass has been created to indicate the degreeof difference between it and the other birds.
All the rest of the birds then are placed in the SubclassNeornithes of which there are several superorders. One superorderwhich is composed exclusively of extinct animals which is theSuperorder Odontognathae and all of the rest of the orders thatyou see here have living representatives. Now there are otherextinct orders that are placed in the Superorder Odontognathaebut we're just taking that one as a representative.
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So on the next page we have a picture of Archaeopteryx - thisanimal is known as a fossil from the Jurassic. It's around 140million years old. It is derived from Saurischian dinosaurs,that's the current understanding.
EVOLUTIONARY HISTORY: There are several recently discoveredfossils of Archaeopteryx that were found in drawers down in thebasement of a British museum where they've been filed away as anon-interesting Saurischian dinosaur. And the reason for that isthat there were no impressions of feathers associated with thesefossils. The original fossil of Archaeopteryx that was discoveredwas just the fossil of a feather. And then they found an intactskeleton surrounded by the impressions of tail feathers and wingfeathers. Knowing what that skeleton looked like, recentinvestigators were able to recognize that these non-interestingSaurischian dinosaur fossils were in fact the fossils ofArchaeopteryx that didn't have feathers associated with them. Sothat serves to emphasize the fact that if it were not thepresence of the impressions of feathers, Archaeopteryx would beconsidered to be a somewhat unusual Saurischian dinosaur.
ANATOMY: Now the anatomy of Archaeopteryx combines a number offeatures which are reptilian, some features which are clearlyavian and then some what we may say in hind-site are"missing" avian features in other words things that wehave come to expect to be parts of the avian skeleton that arenot found in Archaeopteryx. They are really not reptilian, theyare just avian things that aren't there.
Reptilian Features: You can see these if you see the artist'srendition of what Archaeopteryx might have looked like perched ona branch. He has a skull with teeth. We know that modern birds donot have teeth. It has a long bony tail rather than the pygostylethat greatly reduced and compressed the sequence of caudalvertebrae. This one has a long bony tail just like a long lizardstail only with feathers attached to each of the caudal vertebrae.And finally it has 3 very distinct claws on 3 intact separatedigits/fingers. Modern birds have a very greatly reduced"hand" and "wrist" sequence of bones. Sothose are reptilian features of Archaeopteryx. Obviously it alsohad a Saurischian pelvis.
Avian Features: Avian features include a very simple scapula. Nowyou've looked at the scapula when you looked at the turkeyskeleton. Archaeopteryx has a furculum (wishbone) and itobviously has feathers. And those are avian characteristics.
"Missing" Avian Features: Some of the missing aviancharacteristics that we've talked about are the uncinateprocesses (bony extensions from the ribs that sort of strengthenthe rib cage). It has no synsacrum - it has a Saurischian pelvis.And it has no carina or keel on the sternum. Now there are someliving birds that also lack the carina but it is something thatis found in most birds that fly.
So Archaeopteryx is a very unusual animal that is placed in it'sown subclass. It's very much in some ways intermediate betweenthe reptiles and the birds.
The actual evolutionary placement of Archaeopteryx is one whichis debatable. If we make a graph of time, if we put Archaeopteryxon the left side and on this axis we graph a clearly reptilianorganism on the left side and a clearly avian organism on theright side. Here is time so this was 140 million years ago whenArchaeopteryx was found. The next fossil birds are more over tothe right. They have evolved a long way towards beingfull-fledged birds and in the actual interval and time, there'ssomething like 10 million years. Now 10 million years by humanstandards covers the entire evolution of human beings fromobviously very proto-ape types of animals. But the amount ofchange that has actually occurred in going from Archaeopteryx tothese other ancient birds, according to some scientists is anamount of change that you would not expect to occur in 10 millionyears and therefore these scientists hypothesized that there mustbe some ancestor back here in time which is the ancestor of thesemodern birds and Archaeopteryx. In other words, they are sayingthat this is too much change in too short of a period of time,there must be some common ancestor back here. They have coined aname for this hypothetical ancestor as proto-avis or first birdprototypes. The fundamental assumption in this whole argument,this amount of change going from Archaeopteryx to modern birds,the mechanism of that change is Darwinian Natural Selection whichis a process that is only capable of producing very gradualchanges. And if you assume that is the only mechanism that couldaccount for this difference is one that can only produce gradualchanges and that therefore the change is too great, then you goon to say, well there must have been a proto-avis. But there areevolutionary theorists who argue very strongly that naturalselection is not the mechanism that produces big changes in majorgroups of animals. They argue that a different evolutionarymechanism which goes by a number of different terms includingpunctuated equilibrium, macroevolution, and saltatory are theprimary mechanism that produces big changes in major groups ofanimals. They would say that this amount of change is not toomuch to have occurred in 10 million years - a non-gradualmechanism is a mechanism that produces very rapid change in asmall number of generations. So these theorists argue back andforth as to what is the primary mechanism. So there is apossibility the Archaeopteryx is not on the line of descent thatleads to modern birds but there's also the possibility that itis.
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Now the rest of the birds are placed in the Subclass Neornithesand we have a representative of one of these next birds on thispage. This animal that's shown here has the fossil name ofHesperonis. Ornith referring to birds. This is the basis for thename of this particular group Hesperornithiformes. It's found inthe Cretaceous. And there are some members of this order whichstill have teeth. Other than that they have a very avian skeletonwith uncinate processes and keeled sternum and reduction in thedigits and so forth of the claws and things like that.
But some of them still retain teeth and hence the name of theSuperorder Odontognathae which means toothed jaw. But there arealso many other fossil species placed in this superorder whichare also very ancient but which do not have teeth. So not allmembers of the Odontognathae have teeth but many of them do.
When we start looking at the modern birds, the ones that are infact represented by at least single living species, theornithologists start off by listing the flightless birds and theyplace the flightless birds in a Superorder Palaeognathae whichmeans ancient palate. The basic idea which is probably not trueis that these flightless birds can't fly because that's aprimitive condition. And that's almost certainly not true. Thesebirds are almost certainly descended from birds that could fly.
And there are a number of different orders, only 2 of which I'mtelling you about here. One is the Order Rheiformes which as 2living species called Rheas. It's found in South America andthese are fairly highly cursorial animals (adapted for high speedrunning). They live in grassland type of habitats. They get to beabout 4 or 5 feet tall.
The male has a harem of females, 5 or 6 females with whom hecourts and mates and they lay eggs; it takes them about 2 days tomake an egg because it's a pretty good size egg. The eggs weightabout 600 to 700 grams. And the females will lay these eggs intoa nest and he takes care of all the eggs in the nest. And thefemales will be running around feeding, collecting up the energythat they need in order to make an egg and then they'll lay anegg and they'll go run around some more for another couple ofdays, come back and lay another egg. And he waits until he getssomething in the neighborhood of 20 or 25 eggs in a single nest.And then he'll start incubating those eggs, he sits on them dayand night, keeps them warm up to incubation temperature so thatthey start to develop and then the females will continue to bringeggs back for about a week, so that the last eggs that thefemales drop off in the nest have been incubated for a week lessthan all the other eggs but they all hatch at the same time. Sothe developmental period of this species and a number of otherspecies that have highly precocial young, have the ability tovary the length of the developmental period/length of theincubation period. When they get ready to hatch, they hatchsynchronously. The baby birds inside the eggs make littleclicking noises and the translate as "let's all get out ofhere". But the sounds they produce synchronize the hatch andthe eggs that have been incubated for less time hear this soundand they go ahead and terminate their development earlier. Quailsand ducks show the same thing. Some studies show that the babiesthat have terminated their development early are developmentallya little bit behind, they don't have quite as much neuralmuscular coordination as their older siblings.
Rheas that have an incubation period in the neighborhood of about40 days can shorten their total developmental time by about aweek. Quail that have a total developmental time of about 21 dayscan only shorten it by about a half day or 3 quarters of a day.But nevertheless, they do show this phenomenon which is shown ina number of different species that have what we call hatchsynchrony.
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Another order of large flightless birds is the OrderStruthioniformes and these are the ostriches. In fact there'sonly 1 living species of ostrich. These animals are found inAfrica. Anatomically, they are very similar to the 2 species ofrheas that are found in South America.
They are flightless but they have wing feathers that have thebasic structure of a flight feather. They lack the hamuli so theyare nice and soft. They don't have the hamuli, the little hooksthat hold them together but they still have the basic structureof a central rachis (sp) and the proper number of primaryfeathers and everything. So they are obviously descended from abird that could fly. Their cursorial adaptations include areduction in the number of toes. Ostriches are the only birdsthat have only 2 toes and actually one of those is quite a bitlarger than the other so in a way they are similar to a horse inwhich adaptations for high speed running have resulted in thereduction down to a single digit.
Ostriches are the largest of the living birds. They weight around140 to 150 kilograms and they are about 6 feet tall. And theyalso lay the eggs that are the largest of all the species ofbirds. The biggest ostrich eggs weight about 1 and a half kilosand they are about the size of a good size football.
There are a couple of other species of large flightless birds andI'm not going to give you the names of the orders but there are 2types of birds that are found in Australia, the Emu and theCassowaries. And there is a little bird called the Kiwi which isthe only living representative of a family of flightless birdsthat are collectively referred to as the Moas which are found inNew Zealand. And these animals are all placed in the SuperorderPalaeognathae. They are sometimes referred to as Ratites (nocarina). In other words, if you think of a sternum of a bird asbeing the haul of a boat, then most birds that have a keel ontheir sternum look like a sailboat, nice mid-ventral extension.But these birds have a big flat plate for a sternum but there'sno keel on it so it looks more like a raft than a sailboat.
The scientists were really hard-pressed to explain how you couldget a large flightless birds on island continents like Australia,islands like New Zealand and also in Africa, South America untilof course the development of the understanding of continentaldrift which says that at one time all of those southerncontinents were united in a single giant super-continent that wecall Gondwanaland. So probably what happened was that onGondwanaland there was an ancestor that made some initialevolutionary steps towards being a flightless terrestrial birdand when the continent broke apart and the other continents movedoff to their present locations, the animals followed theirsubsequent evolution and so we end off with these ratites havingthis sort of continent distribution.
In most cases, not all of them are plains and grassland livingkinds of animals. The cassowaries are found in scrub habitat.Cassowaries are supposed to be one of the meanest birds thatyou're ever going to meet. If you are unlucky enough to betramping through the scrub of Australia and come across acassowary, you may just end up dead because these guys have avery sharp toe-nail that they use to slice open the bellies ofhumans that come across them in the woods. They are really meananimals.
But many of the others, particularly the rheas and the ostrichesare grassland animals and so in some sense they are likeantelopes, they have adaptations for high speed locomotion toescape from predators and live in grassland type of habitat.Ostriches do not stick their head in the sand, they just looklike they do when they eat. Baby ostriches are highly precocialwith down and everything.
Now when we get into the rest of the birds, we're only going tolook at one superorder which is the Superorder Neognathae. Theorder includes the penguins, the Order Sphenisciformes. There are17 living species of penguins. And these are flightless birdsthat live in the water, they propel themselves through the waterusing their wings. And they are covered with feathers but theyare tiny little feathers that are about 3/4 of a centimeter longcompletely covering their entire body. they are insulated fromthe cold by a layer of blubber that's found underneath the skin.
Their distribution is exclusively in the Southern Hemisphere,that means south of the equator. Of course we tend to associatethem with ice and very cold places and there are a number ofspecies of penguins that are found in the Antarctica on the icyland but there are also species of penguins that reside on thesouthern tip of South America and on the southern ends of Africaand Australia and so forth. And there is even a single speciesthat lives in the Galapagos Islands which is surrounded byextremely cold water due to an ocean current called the Humboltcurrent that comes out of the Antarctic Ocean and sweeps up alongthe western coast of South America and then turns towards thewest and flows pass the Galapagos Islands.
So they are found in association with very cold water. And thereis a functional reason for that. Cold ocean waters are the mostproductive ocean waters. They have the largest amount oforganisms growing in them, various kinds of plants as well assimple animals living in these very cold waters and the penguinsthat feed on a variety of different kinds of fish and things likethat are found in association with cold water because those coldwaters have the greatest availability of food.
Beak Specialization: One of the things that is interesting toobserve about these different groups of birds is the way in whichtheir beaks are specialized for the acquisition of food. Becausethe birds' wings are used exclusively for flight they are notavailable to use in capturing food or collecting food, so theyhave to have some other part of it's body that it can use for theacquisition of food. And since the bird's beak/mouth isspecialized for the acquisition of food in most cases, there area couple of exceptions to that, then the process of mastication(grinding the food) is performed by the gizzard which is amuscular specialization of the esophagus. So when we look at abird we can very frequently see how it's beak is specialized foracquiring a particular kind of food that it is going to feed uponand penguins have one of the recurring beak specializations whichis a long narrow beak with a whole series of little tinyprojections that function like homodont-dentition (like thesimple peg-like teeth of fish and reptiles for example). One ofthe 2 good ways of catching fish that are used by a lot ofanimals are just to have a long narrow beak with a whole bunch oflittle tiny sharp conical projections and grab hold of thatslippery fish and gobble it down.
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The next order that I will talk about is the Order Galliformes.These animals are collectively referred to as the fowl. There areabout 275 species in this order. They include some very familiaranimals like chickens, turkeys, guinea fowl, peafowl/peacock,quail, and pheasants.
A couple of very interesting members of this order that you maynot be generally familiar with include an animal called theptarmigan which is a little quail-like creature that lives on thetundra in the northern parts of North America and Asia and theylive there year-round. They are non-migratory so that they areliving on the tundra during the long arctic winter. They shed alltheir brown feathers and replace them all with white feathers sothat they are very well camouflaged and they live on variouskinds of things that they can dig out of the snow.
Another interesting member of the Galliformes are the birds thatare called the mound-builders and they are also known asbrush-turkeys or megapodes (big foot). The mound-builders areabout the size of a turkey and they are very unusual in whichthey incubate their eggs. What they do is they use these usuallylarge feet that they have to scrape up huge mounds of rottingvegetation. They live in the Australian brush and the mound maybe 10 or 12 feet tall and 25 feet in diameter. The females willfind a male whose made one of these giant mounds and mate withhim and then deposit an egg on the top of the mound. Then sheflies away for about a month and he tends the egg and he stickhis beak down into the mound to measure the temperature and ifit's not hot enough, well then he may pile some more stuff up inorder to insulate it some more. If it's a nice sunny day he mayscrape the stuff away in order for the sun to be able to warm itup. And the female comes back another month and they mate againand she lays another egg and she takes off again. And he'ssitting there slaving away over this mound, piling the stuff up,scraping it off, measuring the temp., and things like that. Thebaby birds take about 60 days to complete their development andthey are unique in that if we think about a precocial species andall of the members of the Galliformes are precocial, what you seewhen a baby chicken or duck hatches is a little bird that'scovered with down which they molt and replace with contourfeathers and flight feathers. Well the baby mound-builders gothrough that entire process in the egg. They start off, they gothrough a phase in their development when they are covered withdown but before they hatch, they go ahead and lose the down andreplace it all with contour feathers so that when the babymegapode, after a couple of months of development, finallyhatches out of the egg, digs out through a meter or so of rottingvegetation, gets up on the top of the mound and flies away. Hedoesn't have to flap his wings or work out his muscles, he justflies away. And they never see their parents which means theydon't learn anything by watching their parents as other birds do.
Most of the Galliformes are granivorous which means they eatvarious kinds of seeds. They have fairly strong conical beaksthat we see in granivorous birds. Almost all of them are veryhighly terrestrial. Most of them retain some ability to fly atleast a short distance, but they do not have the kind of abilitythat will allow them to fly a great distance or be migratory. Sothey end to be resident in a single area and do no fly very greatdistances.
Another order that everybody is fairly familiar with is the OrderAnseriformes, these are the waterfowl. These are the ducks, geeseand swans. These animals have webs between their toes that theyuse for paddling around in the water and all of these speciesspend at least part of their life in water. Although many of themalso spend a part of their life well away from the water.
They have very diverse feeding ecology, many ducks for exampleare filter-feeders like the Mallard. They pull water in and thenclose the mouth and push the water out and filter out the smallplants and animals that are floating on the water. There are somesea ducks that feed on shell fish and have very stout, powerfulbeaks. The Eider duck is one of these sea ducks that feeds onshell fish. There are also types of ducks that are calledmergansers that are piscivores which feed on fish. And these guyshave the same kind of beak adaptations as the penguins, longnarrow beak with bunch of little tiny conical projections.
There are a total of 153 species of Anseriformes. Some of theother feeding adaptations: Geese are terrestrial herbivores -they feed on grasses and sedges and things like that and manyspecies of geese are very highly migratory and spend the summerbreeding on the tundra in the arctic where they are no near waterand spend it all walking around on ground feeding on things. Andthen of course the Swans are aquatic herbivores - they use theirlong graceful neck to reach down to the water plants that areliving in the ponds where they are swimming and they are alsovery highly migratory covering thousands of miles.
The insulation in these animals is not blubber. They don't have abig, thick layer of fat the way the penguins do. Their insulationis in the form of air that's trapped between the feathers. Andtheir feathers are made waterproof by secretions of oil from thestructure called a preen gland. Preening is what a bird does whenit takes care of it's feathers. The preen gland is located rightin front of the pygostyle at the base of their tail and they willreach back there and squeeze this preen gland, get some oil ontheir beak and then they stroke the feathers and they are oilingthe feathers in order to make them waterproof and that's how theystay insulated from the very cold waters.
So there are a number of different kinds of beak specializations:Filter-feeding, strong beaks for feeding on shell fish andvarious things for feeding on the cellulose.
These animals that are herbivores (geese, swans) are going toexhibit a form of digestion which is similar in some ways to thehorse. It's called post-gastric symbiotic digestion of cellulose.So they have a large chamber downstream from the stomach and thecellulose goes in there and there are bacteria that live in thereand the bacteria break down the cellulose and then the animal isable to extract nutrients from the cellulose that has been brokendown by the bacteria.
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And the next order that I need to talk about is the OrderPhoenicopteriformes. Those are the flamingos, there are 7 speciesand they are found in tropical regions of the New World and theOld World. So there are species that are found in Caribbean aswell as Africa.
They are usually found in very large groups. There are reports onsome of the large lakes in Africa there are accumulations of over100 thousand species of individual flamingos nesting and feedingon these lakes at a single time. Of course they come in a varietyof attractive pink colors that different species differ with, theCaribbean flamingo is almost an orange color. But the colors aredeposited in the feathers at the time that the feathers are beingformed and the animal does not have the ability to metabolicallymanufacture the basic organic chemical that's used in makingthose colors. The pigments that are used are called carotenoidsand the animal must extract the basic molecules from their foodsand then they can metabolically modify the molecules in order toproduce the exact shade of pink or orange that they are going todeposit as pigments in the feathers when they are being formed.
So as a consequence, they have to be fed orange colored food whenthey are in the molting process or else the feathers will comeout pure white. So sometimes you see pure white flamingos andthat was one that just wasn't getting the right food.
Beak Specialization: The beak specializations in the flamingo isfor a filter-feeder. They have a big fleshy tongue and they sticktheir beak down in the water and they use that tongue sort oflike a plunger on a pump, they pull a mouthful of water up intotheir mouth and then they close the beak and force the water out.Since they are mammals, they don't have hair. What they have looklike hairs which are the shafts of very small feathers. In otherwords, what looks like a hair on the beak, is really the centralstiffening shaft of a feather without all the little barbs andbarbules around the edge of it. So they are specialized asfilter-feeders.
It seems pretty clear that the flamingos are very closely relatedto the Anseriformes (ducks and geese). When a baby flamingo isborn, it looks almost exactly from a baby goose, it has astraight goose-like beak and a dark grey down coloring and itsduring the development that the beak develops this realpronounced bend in it.
One things that's interesting about the breeding biology offlamingos is if you want flamingos to breed, you have to have afairly large flock. You need to have 40 or 50 flamingos in orderto get them to breed otherwise just a small number of pairs ofmales and females will not do that. And the probable reason forthat is that they have evolved this general tendency which isseen in a number of different species of birds called socialfacilitation. I told you that in most species of birds, thechange in the increasing number of hours of daylight is all thatit takes to get the males ready to breed. I also told you thatthe females will be about half way physiologically prepared tobreed and they have to be courted by a male of their species andthat behavior observed by the female and interpreted by thehigher centers in the cortex of her brain will bring her the restof the way into physiologically readiness to breed. Well inspecies that exhibit social facilitation, the males are notbrought all the way into physiological readiness to breed but themales and the females have to see a whole flock of their ownspecies going through group courtship behaviors.
Social facilitation has a very interesting and believableecological explanation. When there are a number of differentspecies of birds and mammals that specialize in feeding upon theeggs and relatively helpless young of different species of birdsand if you have a hundred thousand flamingos nesting on anAfrican lake, if they did not have this social facilitation thendifferent individuals would breed and lay their eggs and the eggswould be in the nest and then the babies would be in the nest,over a fairly extended period of time, probably in excess ofseveral months, which would mean that some predatory speciescould focus it's entire predatory efforts over a very long periodof time and probably make a pretty good living off of flamingobabies and flamingo eggs. But by evolving social facilitationwhat happens is that the entire flock becomes synchronized intheir reproduction so that you can see this huge flock all doingthese dances and they do these dances for several weeks and thenthey essentially within a matter of a couple of days, theysimultaneously all lay their eggs. The babies are all going tohatch in about exactly the same period of time and then they areall to be independent and able to get away from predators and sothe total period of time when the eggs and the babies areavailable for attack by predators, is greatly reduced and thatmakes it a little bit more difficult for the predators toconcentrate on that species. There's also safety in numbers.
So social facilitation is observed in a number of differentspecies of birds where it's really an attempt to kind of saturatethe ability of predators to wipe out the reproductive efforts ofthe colony.
Flamingos have long legs is so that they can wade around in thedeep water and do their filter-feeding. What you might think isthe knee (see diagram) of the flamingo is really their ankle. Theknee is covered by feathers up near the body.
The next order is the Order Falconiformes ("Raptors").These are the eagles, hawks, falcons and vultures. Most of theseanimals are what we would call diurnal (day active) carnivores.Although some of the very small members of this group areinsectivores. The American Kestrel or the Sparrow Hawk (tinyhawk) which are insectivores, they can hover and they will feedon grasshoppers and other very small insects as well asoccasionally taking a small mouse.
There are a total of 287 species in the order and as I said itdoes include the vultures so we would call those animals carrioneaters - nature's garbage-men. The vultures are one of the fewthat have the sense of smell but most species of birds have nosense of smell at all. Vultures are able to locate their prey bythe smell of the rotting flesh.
The other species, the ones that are carnivores are typicallyspecialized for feeding on various kinds of vertebrate animals sothere are some that feed on other birds like the falcons. Thereare some that specialize in feeding on lots of other differentkinds of mammals, particularly important in the control of rodentpopulations are the buzzards and other hawks that are related tothem. There is one really interesting member of this group thatspecializes in feeding on fish, this is called the osprey andthey are found throughout the northern temperate regions and nearthe oceans where they actually stoop on fish that they can pickup from the surface. There's an African member of this familycalled the secretary bird which specializes in feeding on snakeswhich they drop from the air after grabbing them from the ground.And there's the bald eagle which specializes on feeding on deadfish.
One of the interesting things about the Falconiformes is thatthey have a very large area of their field of vision in whichthey have binocular vision in which both eyes are seeing the sameareas of the field. See diagram below.
In the typical bird/song bird, the eyes are going to be locatedmore towards the side of the head and the field of view which ispossible with these 2 eyes with the retina at the back can see inthis range. And so out here directly ahead of the bird, both eyesare able to see things that are out in front, and this is fairlynarrow. This is the area of overlap from the 2 fields of visionof the 2 eyes. And it's only in this area where both eyes arelooking at something simultaneously that the animal has binocularvision. It's only in the area of binocular vision that the animalhas the ability to judge depth so depth perception (ability forthe brain to neurologically super-impose 2 slightly differentimages and to be able to create a sense of depth) is dependentupon this overlap in the visual fields.
Now as primates, we have very, very extensive of overlap of ourvisual fields. So most birds that are prey species have a verynarrow area of overlap in their visual fields.
Predators like the hawk or falcon, have the eye up here on thefront of the head, they have fairly short beak and so what theyend up with is basically only being able to see the part of theworld that's out there in front of them but a much more extensivefield of overlap between the visual fields; much more area wherethey can judge distance. And the ability to judge distance isabsolutely essential for any animal that is moving around in acomplex 3-dimensional environment.
So prey species of birds will have a narrow area where they canjudge distance which is necessary for their movement in that3-dimensional world, but by having relatively little overlap intheir visual fields, they can see predators coming from almostall around them. Predator species are not too worried aboutsomebody trying to eat them and they are more worried aboutcatching that prey so they have evolved to have more extensiveoverlap in the visual field so that they can do a very good jobof judging the distance to that prey that they are trying tocapture.
So the Order Falconiformes have more extensive overlap in theirvisual fields and that's associated with being predators.
Beak Specialization: The beak specialization in these animals isan exception to the generalization that I made that usuallybird's beaks are specialized for acquisition of prey because inthese animals they have a very strongly hooked beak that can beused to tear apart the body of the animal that they have killedand so their beaks are specialized for at least the beginning ofthe process of mastication (breaking the food down into smallenough pieces so that it can be more rapidly digested). So theirbeaks are more specialized for mastication rather than foracquisition. And the reason for that is that they have powerfulfeet with sharp pointed claws called talons and they are going tobe acquiring their prey using their talons.
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A similar but not really particularly closely related group ofbirds are the Order Strigiformes ("Raptors") - theowls. And there are 146 species of owls. These guys are nocturnalcarnivores - night active hunters. And they also have veryextensively overlapping visual fields just as the Falconiformesdo, however, since they are flying at night/very limited lighttheir sense of hearing is also very important to their ability tolocalize prey so they have very sensitive ears. Anotherinteresting adaptation of the owls is that their feathers have avery distinctive appearance - they are velvety at the uppersurface to muffle the sounds of their wing beats. Hawks of thesame size would make distinctive flapping sounds associated withthe beating of it's wings. This muffling of the sound is reallythe result of an arms race between the prey species that haveevolved particularly sensitive hearing to be able to hear thenoise of an approaching owl and the resulting selection among theowls for something that will make them quieter and less easilydetectable.
Beak Specialization: As I said, owls and hawks are not closelyrelated than they are to any other orders of birds but you willsometimes hear hawks and owls collectively referred to asraptors. Raptor refers to these powerful talons that they have,and the owls also have beaks that are strongly hooked used fortearing up their food and therefore performing the function thatis like the beginnings of mastication.
Owl pellets - many owls will eat small rodents and will tear itapart into a couple of pieces and they swallow the whole entireskeleton of the rodent and everything right down into theirstomach and then they digest away the meat and digestible partsand then they regurgitate the bony leftover remains of the animalthat they ate and they usually do that near their nest and so ifyou go and find a nest of an owl, you find owl pellets. they looklike fecal pellet but they are actually being regurgitated backout of the mouth and they are packed full of bones and fur andit's sometimes possible to get very nice surveys of what speciesof rodents live in the area and are being eaten by the owls bythese owl pellets.
Another order of birds that we're familiar with is the OrderApodiformes. The translation of Apodi means without feet. Andthat's not true. All of the members of this order are very tiny.There are 2 fundamentally different kinds of birds that are foundin this order which may not be terribly closely related to oneanother - swifts and hummingbirds.
Swifts = there are about 80 species of swifts. They have a veryhigh flight speed going about 160 kilometers an hour (over 100miles an hour). They are tiny little flying aerial insectivorescatching the small insects that they feed on while flying. Theyhave a world-wide distribution. They are found throughout theworld. Bird's nest soup is made from the saliva nests of a swiftfrom Southeast Asia.
Hummingbirds = there are about 330 species of hummingbirds. Theydo not have a world-wife distribution. They are found only in theNew World (Central, South and North America). And the center oftheir distribution really is in the tropical areas of Central andSouth America. There are about 7 species of hummingbirds that getinto the U.S. The smallest adult body mass of any species ofbirds is in the hummingbird which weighs about 2.0 grams. Eventhe largest hummingbird is smaller than a sparrow found down inthe tropics. Hummingbirds are specialized primarily but notexclusively for feeding on nectar. They are what we callnectivores. The plants produce the nectar (sugar water) in orderto lure the hummingbirds in and they obtain a very large fractionof their total daily energy needs just simply in the form ofsugar water that's produced by the plants. The plants are doingthat in order to use the hummingbirds as pollinators and there'sa very interesting area of biology called pollination biologythat has grown up in which people have studied the interactionsand evolution of systems in which individual species ofhummingbirds and several different species of plants haveco-evolved in order to produce what works well for both of them.
Hummingbirds have incredibly long tongues that act like abottle-brush on the ends of the tongue. The tongue doesn't actlike a straw, they are not sucking the nectar out of the flower.They stick this kind of bottle-brush tongue down into the area ofthe plant where the nectar is and by capillary action they soakup the nectar and then they pull it back into their mouth.
There have been some very interesting studies done of theinteractions between plants and hummingbirds in mountain meadows(see graph below). Let's make a graph of the time of the summergoing along the bottom and along the side of the graph is thenumber of individual plants that are blooming (they have flowersand are involved in attracting the birds), what you typically seeis that species 1 will have a breeding time like that, species 2like that and so on, there's usually a small overlap between the2 but not very much and so the plants through evolution have sortof divided up the time of the breeding season. The hummingbirdswill be there the whole time, they will be breeding the wholetime and the plants through natural selection have caused theirown particular breeding time to be separated from one another sothat at this time of the year, species 1 is blooming and thehummingbird will specialize in species 1 and do a good job ofpollinating individual plants in species 1 and then species 1drops out and species 2 is blooming and the hummingbird can thenswitch over and do the pollination job for #2, 3, 4 and 5 and soforth. The humming will then be breeding during that period time(a month to 6 or 8 weeks long) because they know that they cancount on the availability of nectar which is necessary of theadults.
In the temperate regions, hummingbirds tend to be highlyterritorial and they are incredible aerial acrobats. They willdefend their plant territories and utilize that as their ownparticular little territory. They produce incredibly tiny eggs.The egg of a hummingbird is about the size of an eraser on apencil.
Because hummingbirds have very high metabolic rates, they alsofind that there are times during the summer, even in these highmountain meadows, where they don't have enough energy to make itthrough the night and so they are an example of one of only acouple of different groups of birds that exhibit daily torpor.When it's particularly cold, these animals will turn off theirmetabolism, they will abandon homeothermy over the night and theywill allow their body temperatures to drop all the way down toenvironmental levels which can be very close to freezing. Nowthis requires a whole series of adaptations in their hearts andother physiological systems in order to be able to survive with abody temperature that may be only 5 degrees Centigrade. But it'ssaves them a lot of energy because they are not having to keeptheir body warm all night. It's like turning the thermostat downon your house. But it is a highly adaptive physiological system,that is they are not giving up, they are not being defeated bythe cold environment because they will arouse themselves and warmback up to the normal avian body temperatures before the suncomes up in the morning so that they are all warmed up, hot andready to go out and start making a living again as soon as thesun comes up. So it's an interesting physiological system thathas been studied in a lot of detail.
A good question would be is if 2 grams is the smallest that youcan be an be an endotherm, well then what about their babies?Which are going to be a lot smaller than that when they are bornand their babies are very highly altricial and have to be keptwarm by an incubating adult. They make their nests out of spiderwebs and real soft things that the bird sits on. You can alsospot these nests because when the baby birds are getting ready todefecate they kind of stick their cloaca over the edge of thenest and defecate out into space so the wall next to the nest isgoing to be all splattered with uric acid.
3rd page of illustrated notes for this date:
The last order of birds that I will talk about is the OrderPasseriformes. And this is the most recently evolved, mostadvanced order of birds and it's the largest one. There arearound 5,000 species in this order, out of the total, around8,200 species of birds all together. So well over half of allspecies of birds are placed in this one order alone.
They have very altricial young in most cases. Many of the speciesthat are found in this order are monogamous in their matingpattern in that both the male and the female adults are requiredto work together in order to bring off the young. Probably a verylarge fraction of the species of birds that you are familiar withare placed in this order, things like swallows, sparrows, robins,blue jays, crows, and ravens. All of these are examples ofPasseriforme birds. The "birds of paradise" arePasserine birds, those are the ones with the amazing colors incourtship behavior displays.
Some of the Passeriformes can be correctly referred to aspasserines although technically only a part of this order arepasserines. They also are sometimes called the perching birdsbecause they do have an unusual arrangement of the tendons intheir feet, although there are lots and lots of other species ofbirds that can perch (sit on a branch). They are also sometimescalled the song birds because of all the birds, they are the onesthat in general have the most melodious calls. Song birds have avery complex structure called the syrinx (an area in theirtrachea) that is responsible for the melodious sounds.
Swallow = aerial insectivores. They have a real wide mouth andusually wide enough to catch insects while they fly through theair. Just fly up to the insect and grab it right out of the air.
Finch = a relative of the sparrow. Most of these are fairlynondescript little brown birds (LBB). Sparrows are the largestsingle family in this order. And they are granivores (seedeating). And their evolution seems to coincide with the evolutionof one of the most recently evolved in wide spread plantcommunities which is the grassland habitat. We tend to think ofgrasslands as being a fairly simple habitat but the plants(grasses) that inhabit those habitats are among recently the mosthighly evolved plants. And so this recently most highly evolvedand large family of birds live in this grassland habitat andutilizes the seeds that are produced by the grasses. They have areal stout conical beak that they can use for breaking up theseeds.
Shrike = they look a lot like the mockingbird. They are about thesize of a robin or mockingbird and they are little miniaturecarnivores. They will kill great big bugs, they even kill littlemice. They have a very slight hook on the end of their beak tohelp them tear their food apart although they don't have powerfultalons, they catch them with their beaks but they have a littlebit of a hook. What's strange about them is that they have tovery opportunistic, in other words if they come across a big bugor a field mouse, they have to go ahead and catch it because theydon't know how long it's going to be before they can catchanother one and if they've just eaten and don't have any room toeat the animal after killing it, what they do is they will saveit by sticking it on the barb of a cactus or on the hooks of abarbed wire fence.
There are lots of other orders of birds that I haven't mentioned.Parrots for example are in their own order, they eat seeds andlots of different kinds of fruits - they are fruigivores. There'sa huge order that includes the seagulls and lots of shore-birdsthat feed on the oceans.