The origin of feathers
The study also showed that this change was accompanied by an increase in beak development that assisted in the diversification of living birds. Are the chicks males or females? See Polyandry Polygamy and Polygamy. Barn Owls in the U. In normal parrots and softbills, there is usually only a left ovary and oviduct.
The villi have the function of providing a vastly increased surface area for the more efficient absorption of the nutrients. The efficiency of the absorption is influenced by the surface area available for the nutrients to move through i. They also provide a means of concentrating the nutrients collection ability once they have moved through the intestine wall. After the duodenum the small intestine forms a coil and is suspended from the dorsal wall of the abdominal wall by a thin membrane called the mesentery.
This membrane carries the blood vessels associated with the intestine. The duodenum starts at the gizzard and forms an elongated loop that is approximately 20 centimetres long. The pancreas lies between the arms of the loop and is attached to, and actually holds together, each arm of the duodenum. Lymphoid tissue in the duodenum is very plentiful and is usually located in the corium. The lymphoid tissue collects the lymph and the lymph vessels transport fluid, other than blood, that is found in the spaces between cells and tissues until it passes into the blood system.
Bile ducts from the gall bladder that are attached to the liver and two to three pancreatic ducts enter the small intestine by a common papilla at the caudal end closest to the rear of the duodenum. The jejunum and the ileum, together about cm long, commence at the caudal end of the duodenum where the bile and the pancreatic duct papilla are located and terminates at the ileo-caecal-colic junction.
This junction is where the small intestine, the two caeca and the colon all meet. This portion of the small intestine is similar in structure to the duodenum except that:. This projection is where the yolk sac was attached during the development of the embryo. The large intestine is very short and does not differ to any extent from the calibre of the small intestine. It runs in nearly a straight line below the vertebrae and ends at the cloaca.
Sometimes this section is referred to as the colon and the rectum the rectum being the terminal section. The bursa of fabricius is located immediately above the cloaca of young birds but disappears when the birds have reached approximately one year old. The two caeca or blind pouches are about centimetres long in the adult. They extend along the line of the small intestine towards the liver and are closely attached to the small intestine along their length by the mesentery.
Each caecum has three main parts:. The large intestine terminates in the front part of the cloaca. The cloaca is a tubular cavity opening to the exterior of the body and is common to the digestive and urogenital tract. The structure of the cloaca is very similar to that of the intestine except that the muscularis mucosa disappears near the vent. It divides into three chambers, each separated by a constriction not readily defined:. The liver is a bi-lobed organ that lies ventrally below and posterior in rear of to the heart and is closely associated with the proventriculus and the spleen.
The right side lobe is larger. The liver is dark brown or chocolate in colour except for the first days when it may be quite pale due to the absorption of lipids fats from the yolk as an embryo.
It weighs approximately 50 grams in adult birds. The capsule, or glissosis, is the membrane that covers the liver and is thinner than that of mammals. The gall bladder lies on the right lobe beneath the spleen. Two bile ducts emerge from the right lobe and one of these originates from the gall bladder and the second provides a direct connection from the liver to the small intestine.
A system of ducts connects the right and left lobes. The liver cells have a high rate of destruction and a good regenerative capacity re-growth ability. Notwithstanding this, in the normal animal, much of the organ is in reserve and can be removed or destroyed without causing undue stress. There are two blood supply systems. One originates from the coelic artery for normal maintenance of the liver as an organ and the second, called the hepatic portal system, transports the nutrients from the small intestine after absorption to the liver.
This latter system enters the liver via two veins one for each lobe. The two blood supply systems join together inside the organ. The liver is drained via the hepatic veins into the posterior vena cava hepatic — relating to the liver; vena cava — one of the main veins that enters the heart.
The liver has a network of sinusoids empty holes in the tissues as in a sponge. The hepatic portal system, the capillaries of the arterial blood supply and the hepatic veins are in close association with each other in these sinusoids. The liver consists of a series of tissue sheets that are two cells thick, with a sinusoid on either side of the sheet.
Bile is made by the cells. The blood vessels, when they enter these sinusoids, become closely associated with them to provide for the easy transfer of material from one system to another. Minute canals called canaliculi that have the task of collecting and transporting the bile are associated with the cells in the tissue sheets. These canals eventually join together to form the bile ducts with one going directly to the intestine and one to the gall bladder before it connects to the small intestine.
This organ has three lobes that occupy the space between the two arms of the duodenal loop. Two or three ducts pass the secretions of this organ into the distal end of the duodenum via papillae common with the ducts from the gall bladder and the liver. These are mainly associated with the production of hormones. In poultry the cells of the islets of Langerhans are less defined than those in mammals.
The functions of the pancreas are:. The pattern of food intake and its passage through the digestive system are the main factors that influence secretory and hence digestive activity. Similar seeds not possessing a strophiolar cleft must depend on abrasion, which in nature may be brought about by microbial attack, passage through an animal, freezing and thawing, or mechanical means. In horticulture and agriculture , the coats of such seeds are deliberately damaged or weakened by humans scarification.
In chemical scarification, seeds are dipped into strong sulfuric acid , organic solvents such as acetone or alcohol , or even boiling water. In mechanical scarification, they may be shaken with some abrasive material such as sand or be scratched with a knife. Frequently seed coats are permeable to water yet block entrance of oxygen; this applies, for example, to the upper of the two seeds normally found in each burr of the cocklebur plant.
The lower seed germinates readily under a favourable moisture and temperature regime, but the upper one fails to do so unless the seed coat is punctured or removed or the intact seed is placed under very high oxygen concentrations.
The most difficult cases of dormancy to overcome are those in which the embryos, although not underdeveloped, remain dormant even when the seed coats are removed and conditions are favourable for growth.
Germination in these takes place only after a series of little-understood changes, usually called afterripening , have taken place in the embryo.
In some species, one winter suffices for afterripening. In others, the process is drawn out over several years, with some germination occurring each year. This can be viewed as an insurance of the species against flash catastrophes that might completely wipe out certain year classes.
Many species require moisture and low temperatures; for example, in apples, when the cold requirement is insufficiently met, abnormal seedlings result. Others cereals, dogwood afterripen during dry storage. The seeds of certain legumes —for example, the seeds of the tree lupin, the coats of which are extremely hard and impermeable—possess a hilum with an ingenious valve mechanism that allows water loss in dry air but prevents reuptake of moisture in humid air. Of great practical importance is stratification, a procedure aimed at promoting a more uniform and faster germination of cold-requiring, afterripening seeds.
Here, two successive cold treatments separated by a warm period are needed for complete seedling development. The first cold treatment eliminates the dormancy of the root; the warm period permits its outgrowth; and the second cold period eliminates epicotyl or leaf dormancy. Thus, almost two years may be required to obtain the complete plant. Seeds of Scotch broom and some Medicago species can be boiled briefly without losing viability.
Ecologically, such heat resistance is important in vegetation types periodically ravaged by fire, such as in the California chaparral , where the germination of Ceanothus seeds may even be stimulated. The major stimulus after a fire is a butenolide called karrikin that occurs in smoke.
Karrikin is derived from the burning of cellulose. Also important ecologically is a germination requirement calling for a modest daily alternation between a higher and a lower temperature. Especially in the desert, extreme temperature fluctuations are an unavoidable feature of the surface, whereas with increasing depth these fluctuations are gradually damped out. A requirement for a modest fluctuation—e. This is advantageous because a seed germinating in soil has to strike a balance between two conflicting demands that depend on depth.
On one hand, germination in deeper layers is advantageous because a dependable moisture supply simply is not available near the surface, but, on the other hand, closeness to the surface is desirable because it allows the seedling to reach air and light rapidly and become self-supporting.
Many seeds are insensitive to light, but in a number of species, germination is stimulated or inhibited by exposure to continuous or short periods of illumination. So stimulated are many grasses, lettuce , fireweed , peppergrass Lepidium , mullein , evening primrose , yellow dock, loosestrife , and Chinese lantern plant. Corn maize , the smaller cereals, and many legumes, such as beans and clover , germinate as well in light as in darkness.
Inhibition by light is found in chive , garlic , and several other species of the lily family , jimsonweed , fennel flower Nigella , Phacelia , Nemophila , and pigweed Amaranthus. Sometimes, imbibed wet seeds that do not germinate at all in darkness may be fully promoted by only a few seconds or minutes of exposure to white light or to karrikin.
Alternations of the two treatments to almost any extent indicate that the last treatment received is the decisive one in determining whether the seeds will germinate.
This response involves the phytochrome system, a mechanism that involves a pigment called phytochrome, which allows green plants to absorb red light. Red light inhibits stem elongation and lateral root formation but stimulates leaf expansion, chloroplast development, red flower coloration, and spore germination.
Such stimulation by red light can be reversed by exposure to far-red light. Laboratory experiments and field observations indicate that light is a main controller of seed dormancy in a wide array of species. The absence of light, for example, was found in one study to be responsible for the nongermination of seeds of 20 out of 23 weed species commonly found in arable soil. In regions of shifting sands, seeds of Russian thistle germinate only when the fruits are uncovered, often after a burial period of several years.
Conversely, the seeds of Calligonum comosum and the melon Citrullus colocynthis , inhabiting coarse sandy soils in the Negev Desert , are strongly inhibited by light. The survival value of this response, which restricts germination to buried seeds, lies in the fact that at the surface fluctuating environmental conditions may rapidly create a very hostile microenvironment. The seeds of Artemisia monosperma have an absolute light requirement but respond to extremely low intensities, such as is transmitted by a 2-mm- 0.
In seeds buried too deeply, germination is prevented. The responsiveness to light, however, increases with the duration of water imbibition. Even when full responsiveness to light has been reached, maximal germination occurs only after several light-exposures are given at intervals. In the field, this combined response mechanism acts as an integrating cumulative rain gauge, because the seeds as indicated become increasingly responsive to light, and thus increasingly germinable, the longer the sand remains moistened.
Certain Juncus seeds have an absolute light requirement over a wide range of temperatures; consequently, they do not germinate under dense vegetation or in overly deep water. Beneath dense canopies, seed germination is inhibited because the green leaves above intercept and absorb red light. In combination with temperature, light in the sense of day length may also restrict germination to the most suitable time of year. In birch, for example, seeds that have not gone through a cold period after imbibing water remain dormant after release from the mother plant in the fall and will germinate only when the days begin to lengthen the next spring.
A number of chemicals potassium nitrate, thiourea , ethylene chlorhydrin, and karrikin and plant hormones gibberellins and kinetin have been used experimentally to trigger germination.
Their mode of action is obscure, but it is known that in some instances thiourea, gibberellin, kinetin, and karrikin can substitute for light.
Natural inhibitors that completely suppress germination coumarin , parasorbic acid, ferulic acid, phenols , protoanemonin, transcinnamic acid, alkaloids , essential oils , and the plant hormone abscisic acid may be present in the pulp or juice of fruits or in various parts of the seed.
The effect of seed-coat phenols , for example, may be indirect; being highly oxidizable, they may screen out much-needed oxygen. Ecologically, such inhibitors are important in at least three ways. Their slow disappearance with time may spread germination out over several years a protection against catastrophes. Furthermore, when leached out by rainwater, they often serve as agents inhibiting the germination of other competitive plants nearby.
Finally, the gradual leaching out of water-soluble inhibitors serves as an excellent integrating rain gauge. Indeed, it has been shown that the germination of certain desert plants is not related to moisture as such but to soil water movement, i. We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind.
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I will copy the information I found:. The author says peanut butter is a danger to our little fellows like the titmice and chickadee. The bird is soon very ill or dead. He says some Chickadees die soon after eating their first meal of peanut butter because after eating they cram their little mouths full of it and carry it away. When they try to deposit the butter in a hiding place it sticks to the roof of their mouths; in the struggle to dislodge it, the butter is packed tighter and the birds choke to death.
It also causes them to become egg bound. Thank you for commenting. But the bottom line is … NO. Peanut butter is not dangerous or lethal to certain birds, AS LONG AS there is a gritty ingredient incorporated into a homemade bird suet recipe, or in a store bought suet cake.
Thanks for the info…I was going to make some suet with a old jar of peanut butter and some seeds but couldnt think of what to use as a binder.
But I also got some great tips from you Thanks again! Just made this for the first time. Thanks for these recipes. We have a small, family owned meat packing plant locally and I get free beef suet from them. Anyhow, I just chop it into chunks and put it in my biggest crock-pot and set it on low over night.
It renders down to a lovely clear liquid albeit a bit smelly liquid, or so says my hubby with just a small bit of meaty pieces left over that I discard. I put baking parchment into loaf pans and set it up in the freezer. Cut in half it fits nicely into the cage type feeders. The birds absolutely love it! Squirrels never touch it though. Anyway, sorry for the lengthy reply. Thanks for giving a helping hand to our feathered friends in cold weather. Thanks for an informative article. With the colder months here, I look forward to giving your recipe a try.
Thanks for the wonderful bird suet recipe!! Now I can make my own and the birds love it! AND for sharing the photo of your birds enjoying it. Thanks for sharing my suet recipe with bird-lovers in your county. I hope everyone finds it easy to make and saves them money over the store-bought suets. Last week I made some suet cakes. I melted fresh tallow and pored it into an empty suet container that was filled with a bird seed mixture. It hardened and looked great. However the birds did not come to eat.
We had some warmer days and I saw the tallow dripping off. How can I prevent that from happening? They ate the store bought ones. I did not put in flour or cornmeal. Would that help to keep the tallow from melting?
Would you want to dine on only fat? I hear that mixing some sand into the suet mix will do the birds some good when eating the suet mix did anyone ever try this or hear of doing that. But, thanks for the comment. I went to the feed store and bought milled corn. Brought it home and put it in the blender to make it more ground. Then I bagged it in 3cup bags.
Makes it easy to mix a quick batch. Thank you so much for your recipe. I have a question: Hello Again… one more question: My question is the Crisco. Are there any health concerns with using hydrogenated vegetable shorting for the birds vs.
My short answer would be: