Week 22 Flashcards
What is the study of birds called?
ORNITHOLOGY.
How many species of birds are there?
c. 9,800 species today- changes all the time. Terrestrial vertebrates- which are incredibly diverse.
Smallest bird-
Largest bird-
Bee hummingbird- 1.5g
Ostrich- 154kg
What is plumage and what are the aspects of it?
In the way they look.
a bird’s feathers collectively.
Extravagant or drab
Where do birds inhabit?
Inhabit about every habitat in the world. Some have become adapted to urban life. Deserts Polar ice Mountains Rainforests
What are the mating systems of birds?
Polygyny
Monogmay
Polyandry
Polygynandry
Some individuals pair for life.
Sometimes one male mates with multiple females.
Sometimes females mate with males but this is rare.
What does Bills relate to?
And what are some examples?
Bills relates to the type of foraging these species do. Probing Sifting Crushing extracting shredding hammering
how are birds classed?
Phylum: Chordata
Subphylum: Vertebrata
Class:Aves
What does the phylogenetic tree tell us about the birds common ancestor?
Shows evolutionary relationships of species which share a common ancestor. It is these last groups of reptiles that the bird’s aves are most closely related to. That is they diverged from a common ancestor more recently than from any other group. So all of these vertebrates represented on the phylogenetic tree have legs. Their common ancestor had legs and this means they are all what are called tetrapods. All but the amphibians also have what are called amniotic eggs. Which makes them amniotes. They all develop through an embryo that is enclosed within a membrane called an amnion. The amnion surrounds the embryo with a watery substance and is probably an adaptation for breeding on land. Amniotes developed directly into a typically terrestrial form, that has limbs and a thick stratified epithelium rather than first entering a feeding laval tadpole stage, which is followed by Metamorphosis, as in the case of the amphibians. You can continue finding features shared by some, but not all of the classes represented here. Feathers is what makes birds unique- they are a modification of the outer skin, so they are this exclusive feature found in all bird species. Archaeopteryx which is the earliest representation of the birds so far discovered that this feather characteristic has been apparent.
What is the Archaeopteryx?
•Very early avian
• Late Jurassic Period
• 155–150 mya
Its the imprints of feathers on the fossil remains, extraordinary well preserved. In terms of size and shape it is not that dissimilar to a magpie.
What are the classic reptilian features that the archaeopteryx has?
- -It had a toothed beak
- -Wing claw
- -Long tail that contained many vertebrate, so it had bones in its tail.
- -Also had feathers, this avian characteristic
- -Was probably a strong running terrestrial bird that could leap into trees, jump among large branches, and perhaps make short flights between trees.
- -Been agreed that they were capable of gliding and perhaps weak flapping, but not of long sustained flights that we associate with many species today.
Although there is huge diversity in the avian world, all birds have a particular characteristic that defines them- What is this feature?
Feathers.
Where did the feathers evolve from?
Which evolved from reptilian scales and birds still have scales on the lower parts of their legs and feet. Compared to scales, feathers are filamentous, soft in texture, flexible, lightweight structures. Apart from being a good diagnostic feature, feathers are such extraordinary evolutionary advances that alone need explanation and they contribute so much to the success of birds.
What are the general characteristics of feathers?
- -Made from the protein keratin- beta keratin which is similar to but different from the Alpha keratins that are found in the skin of all vertebrates.
- -Light, strong & waterproof-
- -No. feathers roughly constant within a species- although they do tend to have more in winter for those species living in cold environments.
- -But there is huge variation in the number of feathers found in different species. Ranging from less than 1000 in some of the hummingbirds. Up to maybe 25,000 in these swans- a huge proportion found in the head and neck of the swan as they spend a chunk of their year in the Arctic conditions that necessitate great insulation.
What are the five main types of feathers?
- Contour
- Down
- Semiplume
- Filoplume
- Bristle
Where are contour feathers found?
Cover the whole body except for the beak and the scaled parts of the legs and feet.
What are the features of contour features?
- Give the bird its characteristic smooth, round shape- streamlining the body and therefore increasing the efficiency of flight.
- Flight feathers (remiges) and tail feathers (rectrices)-
- First level of defence- on outside of the bird so provide the first level of defence for the bird and protection from physical damage that might arise from vegetation or blowing grit. They also shield the skin from the potentially harmful rays of the sun.
- Visual colouring- varied and often eye-catching colours of birds are also mostly related to the contour features. Its those that are the coloured feathers that generate the plumage characteristics that we use to identify birds and that they use in their lives to, for example attract mates.
How do the contour feathers get there colours?
protein pigments
What are these protein pigments?
Melanins (made by bird): black/grey/tan.
Carotenoids (in diet): red/orange/yellow- not generated by the bird itself but is collected in their diets.
What is the intensity of the contour feathers dependent on?
The intensity of these colours is therefore dependent on how much carotenoid is being gathered from the food that the bird is catching. As a consequence, the intensity of these colours can be a good and accurate reflection of how good a bird is as a forager. That means that in some species it’s these reds and oranges and yellows that are used by females to assess the quality of a potential male partner.
Why is ultraviolet reflectance important?
Ultraviolet reflectance is also important- in the last couple of decades, its also become apparent that the feather colours of birds, especially blues and violets are rich in ultraviolet reflectance. Birds have a fourth UV sensitive cone in their retinas, which allows them to see ultraviolet light. And ultraviolet condition therefore plays a vital role in bird behaviour. Birds seem to look rather drab to us, but with this ultraviolet sensitive cone. Birds see the image on the left. All this additional signalling.
Many of the brightest colours in birds are structural colours that result from the physical alteration of ______ ______
incident light.
What are some additional structures of contour structures?
Reflectance- blue/green - produced by the reflection of specific wavelengths of light by different sized particles of melanin contained within the contour feathers.
Interference-iridescence - result from the interference of light waves reflected from the outer and inner surfaces of hollow structures within the feathers.
The perception of interference colours depends on the angle at which the bird is viewed. Iridescent colours therefore kind of flash on and off as the birds changes its position.
What is the structure of a contour feature?
Rachis
Barbs
Barbules and hooks
Rachis-
Barbs-
Barbules and hooks-
Rachis: hollow, central shaft providing backbone.
Barbs: extend either side; site of most pigments.- have small barbules radiating out from them. Are the site of most of the pigments.
Barbules & hooks: create stiffness & flexibility; fasten feathers to one another. These little barbules and hooks link up together to create both a stiffness and a flexibility in the outer surface of the bird. Effectively they’re fastening their feathers to one another to create this continuous, streamlined surface. Preaning is partially used to restore any interlocking of these barbules and hooks that comes undone.
Type II: down feathers
- Smaller than contour feathers-
- Lack barbules and hooklets: not zipped together meaning that they are not locked together.
- Soft and fluffy
- Insulation- they are found closest to the skin of the bird, providing this insulating layer of warmth.
Type III: semiplume feathers
- Intermediate in shape between contour and down
- Found between contour feathers
- Help with insulation
- Help keep form- fill out the body contours, it helps to keep the form in general.
Type IV: filoplume
- Hairlike: few barbs at tip
- Covered by other feathers- not exposed, never found alone and are found next to contour feathers.
- Pressure and vibration receptors- each flight feathers for example might have 8 to 12 filoplumes associated with it. also , unlike other feathers, they have no muscles at their base. But their follicles are endowed with abundant nerve ending, which are sensitive to changes in pressure and vibration. Effectively they are operating as these pressure and vibration receptors.
- Help keep other feathers in order- act as sensory organ for keeping the other feathers, particularly the contour feathers in place and adjusting them in flight and for insulation and during things like bathing.
Type V: bristle
Whereas all birds have the other four types only some have bristle feathers. They are stiff feathers with a few barbs near the base. In those birds that have them, they tend to be found around the eyes and the mouth. They function as sort of guard hairs, protecting those vital organs. They might also act as some sort of sensory organ a bit like the whiskers of a cat. And in some birds, particularly those that catch insects on the wing, they might act as a funnel to funnel those invertebrates towards the beak, enhancing foraging behaviour.
- Stiff, with a few barbs
- Occur around eyes and mouth of some birds
- Protective/filters
- Funnels for insectivores
What are sociable weavers?
a species found in southern africa, each pair of sociable weavers, sometimes with a few little helpers, builds its own nest chamber. But these sociable weavers build collectively together and form these enormous colonies. They are so big sometimes, so many pairs contributing to this overall structure, each with their own next cavity that the weight of the nest can bring down trees or telegraph poles. Because there are lots of nests in the same place, this makes them really attractive to predators like these snakes who come searching for eggs or young chicks. Now the sociable weavers can attempt to chase off snakes, but they don’t have anything other than the ability to mob and yell at them to try and get rid of them. They are aided in getting rid of snakes by pygmy falcons. Often you find a pair of pygmy falcons nesting in one of the chambers in these huge sociable weaver colonies and they eat snakes so they act as a protective force to the sociable weavers. Interspecific interaction.
what are the functions of feathers?
provide colouration
Crypsis
Attraction
Insulation
Flight
What is Function I: crypsis?
- Blending into background to avoid detection
- Predators sneaking up on prey
- Prey escaping predators
- Behavioural traits to match
Cryptic colouration helps hide or camouflage the bird, lowering the likelihood that the individual will be noticed. Its helping them blend into the background to avoid detection for some reason. Some predatory birds have cryptic colouring that guarantees a more dependable approach to prey. For example the typical white colouring of the head, neck and underparts of many fish eating birds helps them to remain undetected by fish looking up into the bright sky. More commonly cryptic colouring is used to escape the attention of predators to avoid being eaten by something nasty. For these protective colourations to be effective, it is sometimes important for certain postures to be adopted and for the bird to remain immoble.
What is Function II: attraction?
- Attract mates
- Males usually brighter than females
- Sexually selected trait
- Brightest males picked by females
Some birds have plumages designed to stand out from background and show off. They are generally used to attract mates. And in many species, its the males who are brightly coloured. That is because often it is females who are the choosy sex and males who are trying to attract selection. As such, this is a sexually selected trait found in one sex and not the other. So many species that have brightly coloured males, females are actually rather drab brown. Theres no need for them to show off. And they are actually better off being less conspicuous and less likely to be spotted by predators. In these species where males are displaying their wares through their plumage, its often the brightest coloured males who are picked by females. That may be inherent quality of the male, or it may be a good forager and able to collect more of these carotenoids that form the reds and oranges and yellows in the plumage.
What is Function III: insulation?
- Primary force driving evolution of feathers
- Vital for endothermy (body temp. c. 40°C)
- Denser plumage in winter
- Fluff out feathers in cold conditions
Insulation is believed to be the primary force driving the evolution of feathers. As endothermic organisms birds maintain a constant body temperature, which can be as high as 40 degrees. The insulation provided by the feathers greatly reduces the amount of energy required to keep up the body heat. And in some birds they moult and have a denser plumage in winter, particularly those living in very cold environments. And just like with crypsis for example then these feather characteristics can be enhanced by behavioural traits. For instance, if you look out on a cold morning in winter here in the UK, you might see a bird looking rather fluffed up as it deals with those early morning temperatures.
what is Function IV: flight?
Feathers are also important in flight, but initially evolved for insulation. So flight followed that initial evolution of veined feathers. Early forays by gliding and weak flapping flight probably fostered additional changes in feather form and function on the wings and the tail particularly. Feather design nowadays gives birds the strength, flexibility and rigidity to support themselves in the air, which of course provides very little support itself. Theres all sorts of characteristics about flight, not just feather form and function.
What is the most basic feather care?
Preening
Why is preening important?
•Restore feather structure, clean plumage, rearrange feathers- depending on the type of maintenance of the bill is used in one of two ways. Either the feather is worked between the mandibles of the bill with a sort of nibbling action. Which is probably important for restoring the relationship between the barbules and the hooks. Relocking those feathers contour feathers together again and for removing dust particles and stale oils. Second way of manipulating in preening is where bills are wiped across the surface of the feather and thats probably important in rearranging them a little bit in drying them out or particularly in the application of preening oils.
Why is applying oils useful for feather care?
•Apply oils from the uropygial gland for waterproofing- these oils come from something known as the uropygial gland and they are crucial for waterproofing the feathers. Not all parts of the body can be reached by a bird’s beak, especially if that beak is a particular shape. Sometimes the head and neck are rubbed with the feet instead of the bill.
Why are feathers fundamental?
Feathers are fundamental to survival and so feather care is of the utmost importance. Because feathers are inert. And do not have an internal system of nourishment and maintenance. Left untended they would become brittle with age and exposure were it not for regular care, which includes the application of waxy secretions produced by the preen gland.
What is allopreening?
In certain species you also see whats known as Allopreening, thats where one individual preens another, either in turn or simultaneously. Studies have shown that although one function of Allopreening is hygienic, reaching bits of the body that an individual cant reach itself. This allopreening may well serve social functions as well.
What is another feather care behaviour?
bathing
Why is bathing useful?
Bathing is another behaviour that is used for feather care, although it is most commonly carried out with water, some birds such as pheasants, use dust instead
What happens after bathing?
After bathing in water, the bird is in a particularly vulnerable condition as its flight efficiency is somewhat impaired. Therefore, it needs a nearby safe place in which to preen itself and to let the feathers dry.
Aside from its role in feather care, bathing may provide a
mechanism to assist in body cooling in hot conditions.
