It is a subspecies…. No exclusively blue or UV-colored pigments are known in vertebrates, but various carotenoid pigments in bird feathers produce UV wavelengths in combination with human-visible yellow, orange, or red colors. Kovacs and Meyers Secondly, it should be rounded and polished, because inside a dinosaur's gizzard any genuine gastrolith would have been acted upon by other stones and fibrous materials in a process similar to the action of a rock tumbler. Now that an owl is back in the box, will you start streaming again?
The origin of feathers
The trunk is the whole body of the bird between the neck and the tail. It is divided into the thorax , abdomen and pelvis. The thorax is bounded by the rib cage, sternum keel and vertebral column backbones.
The abdomen and pelvis aren't separated by any well-defined boundaries. The top part of the trunk is divided into the back and rump. The region between the right and left shoulder blades scapulae is called the interscapular region , and often carries distinctive streaks or colors.
The whole back, combined with the top surface of the wings, is called the mantle. Often these anatomical descriptions are used by judges during bird shows. The side area of the trunk is called the flank. The underside is divided into the breast , belly and undertail. Another area, the crissum , refers to the general area around the vent, along with the undertail covert feathers.
The term, vent , should only be used to describe the actual orifice, and not the general area under the tail. The tail contains the flight feathers called retrices which is Latin for rudders. The retrices are always paired, with the central one lying on the midline. The majority of birds have six pairs of retrices, but the number ranges from 6 to Tail coverts are small feathers that lie over and under the retrices.
Interestingly, the coverts are greatly enlarged in the peacock, and form the eyed feathers of the train. The pygostyle is the end-most bone of the spinal column.
You may be more familiar with the term "the Pope's nose" for this extraneous piece found on a chicken thigh. If this bone has been fractured or injured, a male bird may not be able to successfully copulate with the hen. Moving on to the wing, we find that it is unique, as it is adapted for flight. Many of the bones have become fused, and the skeleton of the hand manus has undergone considerable simplification.
In addition to the bones of the wrist being consolidated, there are only three "fingers. These "fingers" have reduced phalanges our fingers have three phalanges each, except the thumb, which has two.
Most commonly, the alula has one phalanx, the major digit has two, and the minor digit has one. The propatagium is that elastic triangular fold of skin on the leading edge of the wing. This is the area where a tattoo is placed when a bird is surgically sexed. The feathers on the wing are divided into flight feathers remiges , further divided into primary and secondary flights and coverts. The primaries are the last ten wing feathers on the wing, and are numbered from ten to one, outermost to innermost.
The secondaries begin at the first bend of the wing, and are numbered one to twelve, from the bend inward. When wings are clipped, it should never be necessary to cut any feathers other than primaries, no matter which method is used.
The bones of the leg have also been modified. The thigh bone femur is the same as is found in mammals. The knee joint follows at the joint below the femur. The next bone is different from that found in mammals. Several bones have fused to form the tibiotarsus bone. Basically, the ankle bones fused with the bones of the arch of the foot to form one long bone.
There is still a small fibula bone present. The next joint is called the intertarsal joint , and humans don't have one. The bone below that joint is called the tarsometatarsus , which also consists of fused bones. Think of the flamingo leg and how when you watch one walk, it seems as if the "knee" is bending the "wrong" way. That's because the elongated tarsometatarsus looks like the shin bone, so you think that the joint if it was the knee should bend in the other direction. But actually the knee is up in the feathered area of the leg, which DOES bend the same way ours does.
In most birds, the first toe is usually directed backwards, and the other three point forward, and this is technically known as the anisodactyl foot. This type of foot is called the zygodactyl foot. Swifts have a foot adapted for climbing, and all four toes point forward, and this is called the pamprodactyl foot. Emus, rheas, many wading birds and some woodpeckers only have three functional toes, and in most of these birds, it is the first digit the hallux , which is similar to the big toe of man that is lost.
The ostrich has only two toes, with digits I and II being lost. Some of the bones of the avian skeleton are hollow and connected to the air sacs of the respiratory system. Most of the vertebrae, pelvis, sternum and rib bones are hollow and the marrow has been eliminated. The limbs vary in the degree of pneumaticity , and there are pneumatic spaces within the bones of the head, as well.
This is important to reduce the weight of a bird to allow it to be light enough for flight. The skin of birds is different from other animals in several ways. For one, only birds have feathers. Some birds have ornamental outgrowths, characterized by thickened skin that has many blood vessels. For example, some birds have a comb , a bright red vertical projection from the forehead and crown. Some birds also have wattles , which are naked folds of skin that hang down from the mandibles.
Some birds have ear lobes , which are folds of skin, that may be red, white or purple. The snood , also called the frontal process, and is a distensible fleshy process arising on the head between the eyes and nostrils of the turkey.
Turkeys also have caruncles , which are small protuberances of skin on the head and upper neck. The skin of birds contains no sweat glands, so birds rely on evaporative cooling from the respiratory tract. The main gland of birds is the uropygeal gland , and is present in most birds and may be relatively large in some aquatic species. It is absent in the emu, ostrich, many pigeons, Amazon parrots, and the hyacinth macaw, for example.
Another adaptation with avian skin is the brood patch , an area over the breast that becomes thickened, very vascular and the feathers are lost during the brooding period. These modifications promote the transfer of heat from the hen to her eggs. There are seven types of feathers, the contour , semiplume , down , powder down , hypopenna , filoplume and bristle feathers.
The contours cover the surface of the body, and arise from feather follicles. The follicle consists of a living part and a nonliving part. Growing feathers, or blood feathers , have an active blood supply until the feather is grown out completely. If a bird plucks out a feather from a follicle repeatedly, it my eventually destroy the living portion of the follicle, resulting in a follicle that can no longer grow a feather. Feathers molt out when a new feather is developing in the follicle and the old feather is then pushed out.
Normally, a plucked feather will begin to regrow from the follicle immediately, but a cut feather will not be lost until it is molted out.
Most birds replace all their feathers yearly, and this is a continuous process, however, some birds molt during a particular time frame for example, after breeding season, or in the summer. The skin of birds has distinct, well-defined tracts called pterylae that contain the feather follicles for contours. The bare spaces between the pterylae are called apteria. The digestive system has some unique avian features. We have already talked about the crop, the outpouching of the esophagus. The esophagus connects to the crop and then travels through the bones at the top of the keel.
The esophagus then connects to the stomach. The avian stomach is unique. The first portion of it is called the proventriculus , and this is the part with glands in it that secretes gastric juice. The second part of the stomach is called the ventriculus , or gizzard, and it is where digested proteins are broken down and where grinding occurs. When a bird has PDD, proventricular dilation disease, the nerves to the gastrointestinal tract are usually affected, and the proventriculus will become dilated, thin-walled, and impacted with food items.
The ventriculus may also become more mushy and less muscular. Some birds have paired ceca our appendix is really called the cecum , which is the singular of ceca. The big difference occurs when we examine the tail end of the digestive tract. Most people know that birds only have ONE external opening, called the vent , and the internal chamber, or cloaca, that is used for urination, defecation and reproduction.
Inside the cloaca , there are three separate compartments, called the coprodeum , the deepest compartment, and is the terminal end of the rectum. The next cloacal compartment is the urodeum , and this is the middle section that collects urine and urates from the ureters , that drain the kidneys. In the hen, the left oviduct opens into the urodeum. When an egg is travelling through the reproductive tract of the hen, it enters the urodeum before it passes out through the vent.
The last compartment, just inside the vent, is the proctodeum. This compartment contains the avian phallus , if one is present. The phallus differs from the mammalian penis in several ways, the major ones being that it is just a copulatory organ and that is does not function to drain urine. Male ratites ostrich, emu, rhea , ducks, geese, swans and some domestic fowl and turkey possess a phallus.
Male parrots do not. The proctodeum is also the site of the Bursa of Fabricius , an organ that produces cells to fight infections. The bursa is unique to birds and should always be harvested for histopathology if a baby bird dies, because it is often very helpful in diagnosing many avian conditions and diseases.
The bursa begins regressing, called involution , several months after hatching, and will usually be completely involuted by sexual maturity, in most birds.
The urinary system of birds is different from mammals, as birds produce both urine and urates. The kidneys possess two different types of nephrons , the units that filter the blood to remove toxins and products of metabolism. Birds cannot concentrate their urine as well as mammals can. Birds also are uricotelic , meaning that they excrete the end product of nitrogen metabolism as uric acid , which is made in the liver and they excreted from the blood.
Uric acid is the creamy white portion of the dropping. Urine is the clear portion. The feces constitute the third portion of a dropping, and this consists of the solid portion, usually brown or green, depending on what the bird has been eating.
A bird is able to urinate independently of defecating, or passing feces, but most of the time, the bird will pass urine, urates and feces at the same time. And now we know the compartments where these are stored prior to being passed, right? The respiratory system is very unique in birds. Although birds possess a larynx, as we do, they do not use theirs for producing sound. The syrinx is an organ found at the junction of the end of the trachea windpipe with the beginning of the large left and right primary bronchi.
These are air tubes that allow the passage of air into the deeper portions of the respiratory tract. The lungs are found inside the bony ribcage, but not where they are located in a mammal. In mammals, they are found on either side of the heart, and have lobes. No bird lung has lobes, and the liver lies on each side of the heart, instead of the lungs.
The liver is large in birds and is composed of a right and left lobe. Most parrots don't have a gallbladder. Bird lungs are located more against the bones of the back, and are relatively non-expansible. Birds do not have a diaphragm, as mammals do. Birds breathe by expanding the ribcage outward, which draws air in like a bellows. For this reason, it is vital that the chest not be prevented from moving outward when a bird is being restrained for examination or wing clipping, or it will not be able to breathe.
Without going into the detailed anatomy and physiology of the avian respiratory system, I want to mention a few differences between birds and mammals. Birds have paleopulmo and neopulmo , which are two systems of connections between the air tubes, the bronchi and parabronchi. The neoopulmo system is absent in primitive birds, such as the emu and penguin.
In the place of alveoli , which are present in the mammalian lung, birds possess air capillaries instead. The air capillaries are closely entwined with a profuse network of blood capillaries. This is where gasses are exchanged. Birds also have an air sac system. The air sac is connected through a hole in the lung called an ostium. Some bone cavities are occupied by outpouchings of the air sacs.
There are eight air sacs in most species of birds. There are one cervical and one clavicular air sac, and two cranial thoracic , two caudal thoracic , and two abdominal air sacs. Occasionally, an air sac may rupture, and the bird may develop air under the skin subcutaneous emphysema or a large swelling of air in the neck region. When a bird is surgically sexed, the left caudal thoracic air sac is entered by the endoscope. The air sacs allow for easily visualization of the internal organs, usually, and the membrane between the caudal thoracic and abdominal air sacs may need to be punctured by the scope, to better visualize the gonad.
Usually the scope in entered to be able to visualize the left gonad. If the trachea is blocked in a bird having breathing difficulties, or if surgery must be performed around the head and neck, it is possible to insert an air sac tube into one of the air sacs, allowing the bird to breathe through that, instead of the trachea. Our breathing only takes one breath to completely exchange the air in our lungs, while it takes a bird two breaths to completely exchange the air in the system.
This is why an air sac tube can be used for breathing in a bird. The female reproductive system is unique in birds. In most birds, the hen only has a left ovary and oviduct. However, two fully developed ovaries are usually present in birds of prey and the kiwi.
Two oviducts may occur in birds of prey. In normal parrots and softbills, there is usually only a left ovary and oviduct. The ovary contains all of the cells that can turn into eggs. When ovulation occurs, the egg cell and yolk are released from the ovary. Since hens produce eggs, and do not develop the babies inside the uterus, as mammals do, the oviduct is the organ that receives the egg, and then applies the egg white, membranes and shell.
There are five portions to the oviduct and each performs a different function. They are the infundibulum , which receives the egg after ovulation. This is where fertilization usually occurs. Sometimes a hen will lay eggs without a male being present, and in this case, the eggs will be infertile. Chicken eggs purchased at the grocery store are infertile eggs. The next portion of the oviduct is the magnum. It is in this area that the bulk of the egg-white protein is added.
The egg travels next into the isthmus where egg membranes are produced and calcification of shell begins. The next portion of the oviduct is called the uterus , but it is nothing like the uterus of a mammal. The uterus is also called the shell gland, as this is where the shell is put on the egg.
The final portion of the oviduct is called the vagina , and it is here where the sperm are stored in the hen once copulation has occurred. It takes about 25 hours for the egg to travel down the oviduct. The oviduct terminates in the urodeum. Unlike the hen's reproductive tract, the male usually has two functional testicles. However, they are located up inside the body near the kidneys, and are not found externally as they are in mammals.
This is why most birds cannot be sexed by looking at the external characteristics of it, because the testicles or ovary are inside. Some birds have characteristics that identify it as male or female, such as different coloration of feathers.
Eclectus parrots are an extreme example of this, as hens are predominantly red and purple and males are predominantly green. Other birds have more subtle differences. Birds that can be visually sexed are called sexually dimorphic.
Monomorphic birds cannot be sexed by sight and must be sexed by chromosome analysis, DNA analysis or by endoscopy. People often ask me about the heart in birds. It is relatively much larger than that of mammals. It also beats much faster than a mammal's. The heart of a bird can pump much more blood than a man or dog about seven times as much! The blood pressure is much higher in a bird, and it has a remarkable exercise capacity. The heart has four chambers, just like we do. Blood cells in birds are different from those found in mammals.
In birds, the red blood cells still contain a nucleus, and are very large in size, with a lifespan of only days days in man.
Humans and other mammals have a type of white blood cell called the neutrophil , but in birds, these are called heterophils. True lymph nodes , which are common in mammals, are not found in birds, except for certain aquatic birds. Birds and mammals do both possess a thymus , which is another organ of the immune system. Birds possess remarkable abilities to navigate. Pigeons are notorious for their ability to find their way home when taken to strange, far-off locations and released.
It is certain that the sun and stars are dominant orientational cues for birds. These provide compass information only. There is evidence that birds can tell the time of day by using their circadian rhythm with the sun's azimuth direction from the observer.
However, this does not explain how homing pigeons can orientate themselves accurately towards home from release points that are far distant and unfamiliar even when there is complete cloud cover. It is interesting to note that pigeons will miss their home base if they have been shifted six hours out of phase with true sun time. Pigeons may use polarized light or ultraviolet light to help them navigate, and they may use their sense of smell, as well.
Homing pigeons can also detect sound frequencies below 1 Hz, which is much lower than many animals can detect. Birds may be able to detect the infrasound of waves breaking on the shore or wind whistling through mountain tops while flying, helping in navigation. Birds are also extremely sensitive to magnetic changes, and magnetic material has been found in a small area in the head of pigeons, which can aid in a bird locating the direction of the earth's magnetic field.
Gravity and barometric pressure may also be used as clues to aid a bird in navigation. I am convinced that birds are very sensitive to environmental changes. For example, a friend has a pet Quaker parrot, Gaspar, and she had recently moved the cage to a location directly under her television set.
The bird began feather picking immediately, and acted very agitated while the cage was in this location. Frequently small in size and making negligible demands upon their environment, seeds are eminently suited to perform a wide variety of functions the relationships of which are not always obvious: The superiority of dispersal by means of seeds over the more primitive method involving single-celled spores , lies mainly in two factors: The latter factor provides ample opportunity for the development of adaptations for dispersal, such as plumes for wind dispersal, barbs, and others.
Economically, seeds are important primarily because they are sources of a variety of foods—for example, the cereal grains, such as wheat , rice , and corn maize ; the seeds of beans , peas , peanuts , soybeans , almonds , sunflowers , hazelnuts, walnuts , pecans , and Brazil nuts. Other useful products provided by seeds are abundant. Oils for cooking, margarine production, painting, and lubrication are available from the seeds of flax , rape , cotton , soybean, poppy , castor bean, coconut , sesame , safflower , sunflower , and various cereal grains.
Stimulants are obtained from such sources as the seeds of coffee , kola , guarana , and cocoa. In the two great groups of seed plants, gymnosperms and angiosperms, the sporophyte is the dominant phase in the life cycle, as it is also in the vascular cryptogams; the gametophytes are microscopic parasites on the sporophytes. In the typical flowering plant, or angiosperm, seeds are formed from bodies called ovules contained in the ovary, or basal part of the female plant structure, the pistil.
The mature ovule contains in its central part a region called the nucellus that in turn contains an embryo sac with eight nuclei , each with one set of chromosomes i. With very few exceptions e. Pollen grains that land on the receptive upper surface stigma of the pistil will germinate, if they are of the same species, and produce pollen tubes, each of which grows down within the style the upper part of the pistil toward an ovule.
The pollen tube has three haploid nuclei, one of them, the so-called vegetative , or tube, nucleus seems to direct the operations of the growing structure. The other two, the generative nuclei , can be thought of as nonmotile sperm cells. After reaching an ovule and breaking out of the pollen tube tip, one generative nucleus unites with the egg cell to form a diploid zygote i. The zygote undergoes a limited number of divisions and gives rise to an embryo.
The other generative nucleus fuses with the two polar nuclei to produce a triploid three sets of chromosomes nucleus, which divides repeatedly before cell-wall formation occurs.
This process gives rise to the triploid endosperm , a nutrient tissue that contains a variety of storage materials—such as starch , sugars , fats , proteins , hemicelluloses , and phytate a phosphate reserve. The events just described constitute what is called the double-fertilization process, one of the characteristic features of all flowering plants.
In the orchids and in some other plants with minute seeds that contain no reserve materials, endosperm formation is completely suppressed. In other cases it is greatly reduced, but the reserve materials are present elsewhere—e. Other seeds, such as those of beets , contain both perisperm and endosperm. The seed coat, or testa, is derived from the one or two protective integuments of the ovule. The ovary, in the simplest case, develops into a fruit.
More often, however, the seeds are discrete units attached to the placenta on the inside of the fruit wall through a stalk, or funiculus.
The hilum of a liberated seed is a small scar marking its former place of attachment. The short ridge raphe that sometimes leads away from the hilum is formed by the fusion of seed stalk and testa. In many seeds, the micropyle of the ovule also persists as a small opening in the seed coat.
The embryo , variously located in the seed, may be very small as in buttercups or may fill the seed almost completely as in roses and plants of the mustard family.
It consists of a root part, or radicle, a prospective shoot plumule or epicotyl , one or more cotyledons one or two in flowering plants, several in Pinus and other gymnosperms , and a hypocotyl, which is a region that connects radicle and plumule.
A classification of seeds can be based on size and position of the embryo and on the proportion of embryo to storage tissue; the possession of either one or two cotyledons is considered crucial in recognizing two main groups of flowering plants, the monocotyledons and the eudicotyledons.
Seedlings, arising from embryos in the process of germination , are classified as epigeal cotyledons aboveground, usually green and capable of photosynthesis and hypogeal cotyledons belowground.
Particularly in the monocots, special absorbing organs may develop that mobilize the reserve materials and withdraw them from the endosperm; e. In the European, or Scots, pine Pinus sylvestris , for example, the female cones essentially collections of megasporophylls begin to develop in winter and are ready to receive pollen from the male cones in spring.
During the first growing season, the pollen tube grows slowly through the nucellus, while within the ovule the megaspore nucleus, through a series of divisions, gives rise to a collection of some 2, nuclei, which are then individually enclosed by walls to form a structure called the female gametophyte or prothallus. The pollen tube ultimately penetrates the neck of one of the archegonia.
Not until the second growing season, however, does the nucleus of one of the male cells in the tube unite with the oosphere nucleus. Although more than one archegonium may be fertilized, only one gives rise to a viable embryo. The remainder, referred to as endosperm , surrounds the embryo; it is mobilized later, during germination of the seed, a process that occurs without delay when the seeds are liberated from the female cone during the third year after their initiation.
In the Late Carboniferous Period about This primitive ancestral condition of large seeds is reflected in certain gymnosperms Cycas circinalis , 5.
Herbaceous nontropical flowering plants usually have seeds weighing in the range of about 0. Within a given family e. The smallest known seeds, devoid of food reserves, are found in orchids , mycoheterotrophs nongreen plants that absorb nutrients from dead organic matter and live symbiotically with mycorrizal fungi —e. Clearly, seed size is related to lifestyle.
Total parasites obtain food from their host, even in their early growth stages, and young orchids are mycoheterotrophs that receive assistance in absorbing nutrients from mycorrhizal fungi that are associated closely with their roots.
In both cases only very small seeds that lack endosperm are produced. Dodders Cuscuta and mistletoes Viscum , Phoradendron , Amyema live independently when very young and accordingly have relatively large seeds. Many plant species possess seeds of remarkably uniform size, useful as beads e. In wheat and many other plants, average seed size does not depend on planting density, showing that seed size is under rather strict genetic control. This does not necessarily preclude significant variation among individual seeds; in peas , for example, the seeds occupying the central region of the pod are the largest, probably as the result of competition for nutrients between developing ovules on the placenta.
Striking evolutionary changes in seed size, inadvertently created by humans, have occurred in the weed known as gold-of-pleasure Camelina sativa , which grows in flax fields. The customary winnowing of flax seeds selects forms of C.
Seeds form the main source of food for many birds , rodents , ants , and beetles. Harvester ants of the genus Veromessor , for example, exact a toll of about 15,, seeds per acre 37,, seeds per hectare per year from the Sonoran Desert of the southwestern United States. With predation inescapable, however, it must be advantageous for a plant species to invest the total reproductive effort in a large number of very small units seeds rather than in a few big ones.
The mean seed weight of those 13 species of Central American woody legumes vulnerable to bruchid attack is 0. In contrast, the mean seed weight of the 23 species invulnerable by virtue of toxic seed constituents is 3 grams 0. Ecologically, seed size is also important in the breaking of dormancy. Apart from the importance of shape as a factor in determining the mode of dispersal e.
The flatness of the enormous tropical Mora seeds prevents rolling and effectively restricts germination to the spot where they land. In contrast, Eusideroxylon zwageri does not grow on steep slopes, because its heavy fruits roll downhill. The grains of the grass Panicum turgidum , which have a flat and a round side, germinate much better when the flat rather than the convex side lies in contact with wet soil.
In very small seeds, the importance of shape can be judged only by taking into account soil clod size and microtopography of the soils onto which they are dropped. Several seeds have appendages awns, bristles that promote germination by aiding in orientation and self-burial. In one study, for example, during a six-month period, awned grains of Danthonia penicillata gave rise to 12 times as many established seedlings as de-awned ones.
Some plant species produce two or more sharply defined types of seeds that differ in appearance, colour, shape, size, internal structure, or dormancy. In common spurry Spergula arvensis , for example, the seed coat part of the mother plant may be either smooth or papillate covered with tiny nipple-like projections. Here the phenomenon is genetically controlled by a single factor, so all the seeds of a given plant are either papillate or smooth.
Somatic polymorphism may be controlled by the position of the two or more seed types within one inflorescence flower cluster or fruit , as in cocklebur , or it may result from environmental effects, as in Halogeton , in which imposition of long or short days leads to production of brown or black seeds, respectively. Since the different morphs in seed and fruit polymorphism usually have different dispersal mechanisms and dormancies, so germination is spread out both in space and in time, the phenomenon can be seen as an insurance against catastrophe.
While some seeds are dispersed independently of the fruits they matured in, others are dispersed together with the fruit, as is common in many edible fruits, nuts , and cereals. Such a dispersal unit is referred to as a diaspore. The dispersing agents for seeds and diaspores are indicated in such terms as anemochory , hydrochory , and zoochory , which mean dispersal by wind, water, and animals, respectively.
Within the zoochorous group, further differentiation according to the carriers can be made: Or the manner in which the seeds or diaspores are carried can be emphasized, distinguishing endozoochory, seeds or diaspores carried within an animal; epizoochory, seeds or diaspores accidentally carried on the outside; and synzoochory, seeds or diaspores intentionally carried, mostly in the mouth, as in birds and ants.
Snails disperse the small seeds of a very few plant species e. Earthworms are more important as seed dispersers.
Many intact fruits and seeds can serve as fish bait, those of Sonneratia , for example, for the catfish Arius maculatus. Fossil evidence indicates that saurochory is very ancient.
The giant Galapagos tortoise is important for the dispersal of local cacti and tomatoes. The name alligator apple for Annona glabra refers to its method of dispersal, an example of saurochory. Many birds and mammals , ranging in size from mice and kangaroo rats to elephants , eat and disperse seeds and fruits. In the tropics, chiropterochory dispersal by large bats such as flying foxes , Pteropus is particularly important.
Fruits adapted to these animals are relatively large and drab in colour, with large seeds and a striking often rank odour. Such fruits are accessible to bats because of the pagoda-like structure of the tree canopy, fruit placement on the main trunk, or suspension from long stalks that hang free of the foliage. Examples include mangoes , guavas , breadfruit , carob, and several fig species. In South Africa, a desert melon Cucumis humifructus participates in a symbiotic relationship with aardvarks —the animals eat the fruit for its water content and bury their own dung, which contains the seeds, near their burrows.
Furry terrestrial mammals are the agents most frequently involved in epizoochory, the inadvertent carrying by animals of dispersal units. Burrlike seeds and fruits, or those diaspores provided with spines, hooks, claws, bristles, barbs, grapples, and prickles, are genuine hitchhikers, clinging tenaciously to their carriers.
The last-named, with dispersal units highly resistant to damage from hot water and certain chemicals dyes , have achieved wide global distribution through the wool trade. A somewhat different principle is employed by the so-called trample burrs, said to lodge themselves between the hooves of large grazing mammals. Examples are mule grab Proboscidea and the African grapple plant Harpagophytum.
In water burrs, such as those of the water nut Trapa , the spines should probably be considered as anchoring devices. Birds , being preening animals, rarely carry burrlike diaspores on their bodies. Small diaspores, such as those of sedges and certain grasses , may also be carried in the mud sticking to waterfowl and terrestrial birds. Synzoochory, deliberate carrying of diaspores by animals, is practiced when birds carry seeds and diaspores in their beaks.
The European mistle thrush, Turdus viscivorus , deposits the viscid seeds of European mistletoe Viscum album on potential host plants when, after a meal of the berries, it whets its bill on branches or simply regurgitates the seeds.
The North American Phoradendron and Australian mistletoes Ameyema are dispersed by various birds, and the comparable tropical species of the plant family Loranthaceae by flowerpeckers of the bird family Dicaeidae , which have a highly specialized gizzard that allows seeds to pass through but retains insects. Plants may also profit from the forgetfulness and sloppy habits of certain nut-eating birds that cache part of their food but neglect to recover everything or drop units on their way to the hiding place.
Secondarily, rodents may aid in dispersal by stealing the embedded diaspores and burying them. In Germany an average jay may transport about 4, acorns per season, over distances of up to 4 km 2. Woodpeckers, nutcrackers, and squirrels are responsible for a similar dispersal of Pinus cembra in the Alps near the tree line. Most ornithochores plants with bird-dispersed seeds have conspicuous diaspores attractive to such fruit-eating birds as thrushes , pigeons , barbets members of the bird family Capitonidae , toucans , and hornbills family Bucerotidae , all of which either excrete or regurgitate the hard embryo-containing part undamaged.
Such diaspores have a fleshy, sweet, or oil-containing edible part; a striking colour often red or orange ; no pronounced smell; a protection against being eaten prematurely in the form of acids and tannins that are present only in the green fruit; a protection of the seed against digestion —bitterness, hardness, or the presence of poisonous compounds; permanent attachment; and, finally, absence of a hard outer cover.
In contrast to bat-dispersed diaspores, they occupy no special position on the plant. Examples are rose hips, plums , dogwood fruits, barberry , red currant , mulberry , nutmeg fruits, figs , blackberries , and others. The natural and abundant occurrence of Euonymus , which is a largely tropical genus, in temperate Europe and Asia, can be understood only in connection with the activities of birds.
Birds also contributed substantially to the repopulation with plants of the island Krakatoa after the catastrophic eruption of Birds have made Lantana originally American a pest in Indonesia and Australia ; the same is true of wild plums Prunus serotina in parts of Europe, Rubus species in Brazil and New Zealand , and olives Olea europaea in Australia.
Hard and often shiny red or black and red, many such seeds deceptively suggest the presence of a fleshy red aril and thus invite the attention of hungry birds. Mediterranean and North American harvester ants Messor , Atta , Tetramorium , and Pheidole are essentially destructive, storing and fermenting many seeds and eating them completely.
Other ants Lasius , Myrmica , and Formica species eat the fleshy, edible appendage the fat body or elaiosome of certain specialized seeds, which they disperse. Most myrmecochorous plants species of violet, primrose , hepatica , cyclamen , anemone , corydalis , Trillium , and bloodroot belong to the herbaceous spring flora of northern forests.
Tree poppy Dendromecon , however, is found in the dry California chaparral ; Melica and Centaurea species, in arid Mediterranean regions. The so-called ant epiphytes of the tropics i. The ancestral forms of these hairs must have served in wind dispersal. The primary ant attractant of myrmecochorous seeds is not necessarily oil; instead, an unsaturated, somewhat volatile fatty acid is suspected in some cases.
The myrmecochorous plant as a whole may also have specific adaptations; for example, cyclamen brings fruits and seeds within reach of ants by conspicuous coiling shortening of the flower stalk as soon as flowering is over.
In the modern world, wind dispersal although numerically important reflects the climatic and biotic poverty of certain regions; it is essentially a feature of pioneer vegetations. The flora of the Alps is 60 percent anemochorous; that of the Mediterranean garrigue a scrubland region is 50 percent.
By making certain assumptions e. This calculation yields values of 10 km 6 miles for dandelion Taraxacum officinale and 0. Storms result in higher values—30 km 20 miles for poplar and km miles for Senecio congestus. Too much success in dispersal may be ecologically futile, as exemplified by certain Florida orchids that arise from windblown West Indian seeds but do not multiply because of the lack of specific pollinators, usually certain bees or wasps.
Anemochorous diaspores can be subdivided into flyers, dust diaspores, balloons, and plumed or winged diaspores; rollers, chamaechores or tumbleweeds ; and throwers, ballistic anemochores. Not surprisingly, it is practiced mostly by total parasites , such as broomrapes in which the finding of the specific host is a problem , and mycoheterotrophs.
The inflated indehiscent pods of Colutea arborea , a steppe plant, represent balloons capable of limited air travel before they hit the ground and become windblown tumbleweeds. Winged fruits are most common in trees and shrubs , such as maple , ash , elm , birch , alder , and dipterocarps a family of about species of Old World tropical trees.
The one-winged propeller type, as found in maple, is called a samara. When fruits have several wings on their sides, rotation may result, as in rhubarb and dock species. Sometimes accessory parts form the wings—for example, the bracts small green leaflike structures that grow just below flowers in Tilia linden.
Seeds with a thin wing formed by the testa are likewise most common in trees and shrubs, particularly in climbers— jacaranda , trumpet vine, catalpa , yams , butter-and-eggs. Most famous of these is the seed with a giant membranaceous wing 15 cm [6 inches] long of the Javan cucumber Alsomitra macrocarpa , a tropical climber.
Many fruits form plumes, some derived from persisting and ultimately hairy styles, as in clematis , avens , and anemones ; some from the perianth, as in the sedge family Cyperaceae ; and some from the pappus, a calyx structure, as in dandelion and Jack-go-to-bed-at-noon Tragopogon. Plumed seeds usually have tufts of light, silky hairs at one end rarely both ends of the seeds—e.
In woolly fruits and seeds, the pericarp or the seed coat is covered with cottonlike hairs—e. In some cases, the hairs may serve double duty, in that they function in water dispersal as well as in wind dispersal. Poppies have a mechanism in which the wind has to swing the slender fruitstalk back and forth before the seeds are thrown out through pores near the top of the capsule.
Many marine, beach, pond, and swamp plants have waterborne seeds, which are buoyant by being enclosed in corky fruits or air-containing fruits or both; examples of these plants include water plantain , yellow flag, sea kale , sea rocket , sea beet, and all species of Rhizophoraceae, a family of mangrove plants.
Sea dispersal of the coconut palm has been well proved; the fibrous mesocarp of the fruit, a giant drupe , provides buoyancy.