APPENDIX Defined for English Language Learners
What Is The Difference. It extends from the bones of the skull, face and mouth — which make up the cranium — down to the sacrum, or tailbone. A slit like opening, the glottis opens into the laryngotracheal chamber. Join our Newsletter Thank you for subscribing! The arterioles divide to form blood capillaries which unite to form venules. You may know dandelion as a stubborn weed in your garden, but this plant may also benefit your health. The space or cavity lined by parietal peritoneum externally and visceral peritoneum internally is known as coelom or cavity.
About the author
The use of the gizzard system has the potential advantages that intake rate is not limited by chewing, that no investment in dental tissue is necessary, and that dental wear is not a determinant of senescence as observed in mammals.
The absence of age-dependent tooth wear might even be a contributing factor to the slower onset of senescence in birds as compared to mammals. On the other hand, the use of a gizzard requires the intake of suitable grit or stones—an action that represents, in the few studies where this has actually been quantified in birds, a relevant proportion of feeding time Fritz et al. Gastrointestinal tracts of a carnivorous hawk, an omnivorous chicken, and 4 herbivorous birds.
Note larger size of crop in omnivore and herbivores, and particularly in hoatzin. Ceca are small in hawks and relatively large in grouse. Although ceca are relatively small in Hoatzins , Emus, and Ostriches, an expanded foregut Hoatzins , a much longer midgut Emus , or a much longer colon Ostriches compensates for this From: Stevens and Hume Over-reliance on the passive pathway provides metabolic advantages and ecological constraints.
It does provide birds with an absorptive process that can deal with rapid and large changes in intestinal sugar concentrations. The passive pathway is also energetically inexpensive to maintain and modulate.
However, passive absorption through the paracellular pathway is dependent on concentration gradients. In the absence of a transport system that selects which materials to absorb, this non-discriminatory pathway may also increase vulnerability to toxins, and thus constrain foraging behavior and limit the breadth of the dietary niche of the birds. Another problem is that when luminal sugar concentrations are lower than those in plasma, glucose may diffuse back into the lumen.
Cross-section of the intestine ileum of a Spotted Tinamou Nothura maculosa. Villi are lined with columnar epithelium EP , including goblet cells arrows that secrete mucus. The muscle layer includes longitudinal fibers MI on the perimeter, circular fibers Mc , and additional longitudinal fibers at the base of the villi muscularis muscosae; MM From: Chikilian and de Speroni Blue-headed Parrots at clay lick. Meyer-Rochow and Gal determined that the pressures involved could be approximated if they knew the 1 distance the feces traveled, 2 density and viscosity of the material, and 3 shape, aperture, and height of the anus above ground.
How penguins choose the direction of defecation, and how wind direction factors into that decision, remain unknown. Avian Pancreas tissue Source: The Avian Digestive Tract. Avian geophagy and soil characteristics in southeastern Peru. Luminal morphology of the avian lower intestine: Histological aspects of the stomach proventriculus and gizzard of the Red-capped Cardinal Paroaria gularis gularis. Comparative study of the digestive system of three species of tinamou. Crypturellus tataupa, Nothoprocta cinerascens , and Nothura maculosa Aves: Journal of Morphology Journal of Experimental Zoology Rictal bristle function in Willow Flycatcher.
Dysplastic koilin causing proventricular obstruction in an Eclectus Parrot Eclectus roratus. Journal of Avian Medicine and Surgery Anatomy and physiology of the digestive system in fowl. Pages in Proc. An histological and histochemical analysis of the inner lining and glandular epithelium of the chicken gizzard. American Journal of Anatomy An ecomorphological study of the raptorial digital tendon locking mechanism.
Dietary and developmental regulation of intestinal sugar transport. Digesta retention patterns in geese Anser anser and turkeys Meleagris gallopavo and deduced function of avian caeca. Comparative Biochemistry and Physiology A Histological and global gene expression analysis of the 'lactating' pigeon crop. Vultures of the seas: Evolution of the structure and function of the vertebrate tongue. Journal of Anatomy Light and scanning electron microscopic study of the tongue in the cormorant Phalacrocorax carbo Phalacrocoracidae, Aves.
Functional morphology of the tongue in the nutcracker Nucifraga caryocatactes. A tropical horde of counterfeit predator eyes. Instructed learning in the auditory localization pathway of the Barn Owl.
The morphology of the bill apparatus in the Steller's Sea Eagle. Wild Bird Society of Japan, Tokyo. Use of dung as a tool by burrowing owls. The integration of energy and nitrogen balance in the hummingbird Sephanoides sephaniodes. Does gut function limit hummingbird food intake? Physiological and Biochemical Zoology Pressures produced when penguins pooh—calculations on avian defaecation. Scare tactics in a neotropical warbler: Gliding flight and soaring.
Theoretical Ecology Series, vol. Modelling the flying bird C. Structure, form, and function of flight in engineering and the living world. Phenotypic flexibility and the evolution of organismal design.
Trends in Ecology and Evolution The hummingbird tongue is a fluid trap, not a capillary tube. Between air and water: Use of prey hotspots by an avian predator: Structure and mechanical behavior of a toucan beak.
Movement and direction of movement of a simulated prey affect the success rate in Barn Owl Tyto alba attack. Musculoskeletal underpinnings to differences in killing behavior between North American accipiters Falconiformes: Accipitridae and falcons Falconidae.
Journal of Morphology, online early. Le Bohec, and Y. Adjustments of gastric pH, motility and temperature during long-term preservation of stomach contents in free-ranging incubating King Penguins. Journal of Experimental Biology A tough nut to crack.
Adaptations to seed cracking in finches. Cost-benefit analysis of mollusc-eating in a shorebird. Optimizing gizzard size in the face of seasonal demands. How do woodpeckers extract grubs with their tongues? Why do woodpeckers resist head impact injury: Functional morphology of raptor hindlimbs: The turning- and linear-maneuvering performance of birds: Canadian Journal of Zoology Hummingbird jaw bends to aid insect capture. A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems.
I - Introduction to Birds. VII - Circulatory System. Back to Avian Biology. Drawings of the digestive tracts of A a Greylag Goose and B a Wild Turkey and retention times of a solute, 2-mm particles, and 8-mm particles in the goose and turkey digestive systems Figure from Frei et al. The closed, air-filled spaces reduce overall weight without loss of rigidity. The capillary ratchet mechanism Surface tension transport of prey by feeding shorebirds: The serrated leading-edge feather of an owl Norberg Vortex generators on an airplane wing.
Fish-eating species like cormorants below - typically have small, undifferentiated tongue because fish are often swallowed whole. Representative caterpillar false eyes and faces. In some, like woodpeckers, the 'sticky' saliva aids in capturing prey. In others, like swifts, saliva is used in nest building see photo below. The muscular walls of the esophagus produce wave-like contractions peristalsis that help propel food from the oral cavity to the stomach.
Anhinga swallowing a large fish. HCL and pepsinogen are secreted by the deep glands see photomicrograph below. Pepsinogen is converted into pepsin a proteolytic, or protein-digesting, enzyme by the HCl. The cuticle is secreted by simple tubular glands see photomicrograph below. Grinding action may, particularly in seed-eating birds, be assisted by grit and stones deliberately ingested. The avian gastrointestinal tract, unlike that of mammals, executes distinct reverse peristaltic movements that are critical to optimal digestive function Duke The gastric reflux allows material in the gizzard to reenter the proventriculus for additional treatment with acid and pepsin.
Villi are projections from the intestinal wall that increase the amount of surface area available for absorption. Further increasing the surface area are the numerous microvilli of the cells lining the surface of the villi. Inside each villus are blood vessels that absorb nutrients for transport throughout the body.
Caeca are histologically similar to the small and large intestines and found in a wide variety of birds. In these large ceca, food particles are acted upon by cecal secretions, bacteria, and fungi and nutrients can be absorbed. Lymphoid ceca are not important in digestion but contain lymphocytes white blood cells that produce antibodies Clench At various times and under various conditions, ceca are the site for 1 fermentation and further digestion of food especially for the breakdown of cellulose and absorption of nutrients, 2 production of antibodies, and 3 the use and absorption of water and nitrogenous components Clench The bursa is most prominent in young birds and serves as the area where B-lymphocytes the white blood cells that produce antibodies are generated T-lymphocytes are generated in the Thymus.
Bile emulsifies fats or, in other words, breaks fats down into tiny particles. Emulsification is important because it physically breaks down fats into particles than can then be more easily digested by enzymes lipase produced by intestinal cells and the pancreas. This 'juice' contains a bicarbonate solution that helps neutralize the acids coming into the intestine from the stomach plus a variety of digestive enzymes. The enzymes help break down fats, proteins, and carbohydrates.
The pancreas also produces the hormones insulin and glucagon which regulate blood sugar levels cells that produce these two hormones make up the 'islets of Langerhans', one of which is represented by the light-colored, circular structure in the photomicrograph below. Hit 'Reload' or 'Refresh' to View Again!
Particle retention time hr. Flamingos use a series of projections, or lamellae, to filter tiny food items from debris in the water. Wrens use their thin, probing bill to capture small insects. Curlews use their long bill to probe mudflats for small invertebrates. Finches do not simply bite the seeds; instead; the lower mandible is moved toward the tip of the bill in a slicing motion. When most of the coat has been cracked or removed, the lower mandible is moved from side to side to remove the rest of the shell, thus releasing the kernel.
Some large finches also have raised hard surfaces in the upper palate that function as anvils so large seeds can be held firmly while the lower mandible slices and cracks the sides of the seed. As tricky as nutcracking sounds, most birds accomplish it rapidly, shelling small seeds in a few seconds and large finches can crack open and devour a large seed or nut in less than twenty seconds.
Big mouths get hummingbirds an in-flight meal - Hummingbirds have bendy lower beaks to help them catch insects Yanega and Rubega The flexibility allows long-beaked birds to open their mouths wide enough to hunt on the wing.
Hummingbirds use their long, narrow beaks to probe flowers for nectar, but they also need insects for essential nutrients. It wasn't clear how they could catch them; birds that hunt flying insects usually have short beaks to help them open their mouths wide.
Pilcher, Nature Science Update. The force produced by talons may be related to time of activity. Owls hunt when light levels are low so if an attacking owl misses its prey, relocating it may be difficult. Hawks are diurnal hunters and can use visual cues during and after an attack.
If unable to subdue prey initially, they can relocate prey visually and catch it. Given the morphological differences and hunting behaviors of these raptors, how well do those characteristics relate to prey-size selection? Eastern Screech-Owls prey on insects, small birds, and small mammals. Red-tailed Hawks subsist primarily on rodents and larger mammals such as skunks and rabbits.
Red-shouldered Hawks , like Barred Owls, subsist mainly on medium-sized mammals such as squirrels and chipmunks, but also prey on frogs and salamanders. American Kestrels , like Eastern Screech-Owls, eat mostly insects and small mammals.
Bristles occur most prominently around the eyes "eyelashes" , the lores, the nostrils, and around the rictus corners of the mouth. Not all birds have bristles. Rictal bristles are prominent in many insectivorous birds, particularly aerial insectivores like nightjars Order Caprimulgiformes and flycatchers Family Tyrannidae , and may be used as sensory organs to help locate and capture prey, much like mammals use whiskers.
In addition, bristles around the mouth may help protect the eyes from food items a bird is trying to capture Conover and Miller The photo to the right shows the rictal bristles of a Hooded Warbler. Goose tongue -- The dorsal surface of the tongue of Middendorff's Bean Goose Anser fabalis middendorffii has an anterior region that extends for five-sixths of its length plus a posterior region. Large conical papillae indicated by arrowhead to the right are located in a row between the anterior and posterior regions.
On both sides of the anterior region, lingual papillae are compactly distributed, and small numbers of large conical papillae are found between the lingual papillae.
The dorsal surface of the tongue is covered by numerous fine processes, which help hold food on the tongue's surface. The taste buds of birds may be located in the upper beak epithelium, in the anterior mandible, and the mandibular epithelium posterior to the tongue. Some taste buds are also located ventrolaterally on the anterior tongue. Arrows show lingual hairs on the lateral sides. Lingual papillae arrows are compactly distributed on the tongue, and large conical papillae arrowhead are scattered among them.
Energy and nitrogen balance in a hummingbird -- Keeping fit and healthy on a low-fat, fiber-free diet isn't easy, but despite the nutritional disadvantages of life on a liquid lunch, hummingbirds flourish by supplementing their nectar intake with tiny arthropods.
But the beneficial snacks come at a high metabolic price; flies don't sit still, so hummingbirds work hard chasing their protein. Back in the lab, the team prepared nectar solutions with different concentrations of amino acids to see how much protein the birds needed to maintain a stable body weight.
By filming the birds as they sipped from feeders, they measured the amount of energy and nitrogen that the birds consumed. To calculate the bird's nitrogen uptake, they also needed to know how much waste nitrogen the birds lost. So, they collected all of the birds' feces, making sure that none dried out, and measured the nitrogen content. Not surprisingly, the birds that were fed small amounts of protein began losing weight quickly, even though they were able to sip as much high-energy nectar as they wanted.
However, the birds that were fed 1. What does that translate to in terms of flies? The birds that had a reduced nectar supply also maintained a stable weight, although they went into torpor overnight to conserve energy. But the birds fed flies alone began losing weight, no matter how hard they worked to feed themselves.
She suspects that although the flies should supply all of the hummingbirds needs, the birds simply have to work too hard to catch flies to rely on them as their soul food source. Flush—pursuit foragers use exaggerated and animated foraging movements to flush potential insect prey that are then pursued and captured in flight. The Myioborus redstarts comprise 12 species of flush—pursuit warblers found in montane forests of the American tropics and subtropics.
All members of the genus have contrasting black-and-white tail feathers that are exposed by spreading the tail during foraging. Mumme examined plumage pattern and tail-spreading behavior to see how they affected flush—pursuit foraging performance of the Slate-throated Redstart Myioborus miniatus in Costa Rica.
Although flycatching was the most common foraging tactic used by Slate-throated Redstarts, flush—pursuit prey attacks occurred more frequently following hops in the spread-tail foraging posture than hops in more typical warbler-like posture, suggesting that tail-spreading behavior assists in startling and flushing potential insect prey.
The hypothesis that the white tail feathers enhance flush—pursuit foraging was tested by means of a plumage-dyeing experiment. After locating nests, Mumme captured the male and female and assigned one member of each pair to the experimental treatment group; its mate served as a control. For experimental birds, a permanent marker was used to blacken the white tips of the three outer retrices.
For experimental birds, only 7. These results indicate that white tail feathers are critically important in startling potential prey. The owls ate 10 times more beetles when the dung was present, suggesting the waste did not build up by accident. Burrowing Owls make their nests in small tunnels, and place a variety of debris, including dung, at the entrance.
After finding that Burrowing Owls also had a high concentration of dung beetles in their diet, Levey et al. To test this hypothesis, they cleared all nest entrances at two colonies of owls of debris, then one owl colony had a typical littering of dung applied while the other was left bare. After four days each entrance was again completely cleared and the situation was reversed. Analysis of the owls' waste clearly showed that when dung was present, the owls feasted on ten times more dung beetles.
As Levey says, "this experiment demonstrates that tool use makes a difference to a wild animal". Although it may be tempting to conclude the owls are clever enough to devise this trap, Levey explained: Instead, the baiting may simply have evolved, as owls who happened to collect more dung had a better diet and therefore bred more successfully. A Price Worth Paying -- Birds don't need teeth to grind their food; they solve the mashing problem with a powerful gizzard.
But not all gizzards are equal. In fact, Red Knots' gizzards grow larger when the birds put on weight preparing for migration. But they also change size throughout the year. What causes such changes in gizzard size? Long-term preservation of stomach contents in incubating King Penguins -- Male King Penguins Aptenodytes patagonicus are able to store undigested food in their stomach for up to 3 weeks during their incubation fast.
Such an adaptation ensures hatchling survival if their mate's return is delayed. Using small electronic recorders, Thouzeau et al.
The pH could be maintained at values as high as 6 throughout the incubation fast, a pH unfavorable for avian gastric proteinase activity. Gastric motility was markedly reduced for most of the incubating birds, with lower motility probably associated with a better conservation of stomach content.
The fact that stomach temperature of incubating birds did not show a daily rhythmic fluctuation as seen in non-breeding birds could be due to temperature constraints on embryo development. Thus, this study demonstrates substantial adjustments of pH and gastric motility in incubating King Penguins, which may contribute to the inhibition of digestive gastric processes. Glucose transport in birds -- In contrast with regulation of intestinal glucose transport in mammals, amphibians and fish, intestinal glucose transport does not change with dietary carbohydrate in most birds.
This is interesting, because the diets of many birds change with seasons, and the levels of carbohydrate in those diets also vary with season. The absence of dietary modulation of glucose transport in birds may be due to the predominance of passive glucose transport, probably occurring through the paracellular pathway i.
If transport were largely passive and dependent on transepithelial concentration gradients, then there would not be any need for specific changes in carrier-mediated active transport. For example, passive absorption of nutrients such as fat-soluble vitamins is not subject to modulation by diet.
Brightsmith and Muñoz-Najar observed ten species of psittacids, three species of columbids, and two species of cracids consuming soil from banks of a river in Peru. They found that preferred soils were deficient in particles large enough to aid in the mechanical breakdown of food and help digestion.
Lipid molecules lipid means fat must be broken down into very small globules in order to be taken up by the microvilli in your small intestine. Lipase is aided by bile from the gallbladder. Starchy and sugary foods consist mostly of carbohydrates. Carbohydrates are long strings of sugar molecules. Pancreatic amylase breaks down starch molecules into oligosaccharides. Lactose is the sugar in milk. Without lactase, our intestines are unable to digest milk products, resulting in a gaseous, upset, sick feeling, with diarrhea, and flatulence.
Protein digestion begins in the stomach with chemical and mechanical breakdown into smaller protein pieces and polypeptide chains. Polypeptides are long chains of amino acids. Amino acids are absorbed by the microvilli of the small intestine. The pancreas secretes trypsin and chymotrypsin into the duodenum of the small intestine to break down proteins into amino acids.
Within the microvilli of the small intestine are networks of capillaries and lymph vessels called lacteals. Simply put, nutrients diffuse into your blood vessels through chemical and electrical gradients: Fat molecules are taken up by lacteals; little balloons of lymph tissue that merge with other lacteals to form lymphatic vessels responsible for circulating lymph fluid. Fats in the bloodstream are called chylomicrons. Not all digested matter from our food makes it to the bloodstream. Whatever is left after our small intestine sucks out all of the nutrients passes onto our large intestine.
Here, water and salt are reclaimed for the body, the waste is concentrated and comes out our anus as stool. What I find really interesting is that between the mouth and the anus is one, long continuous, open ended tube. What goes in, must come out.
At risk of being too gross, I will mention that the color of your stool can be indicative of a number of illnesses of the pancreas, the liver, the gallbladder and more; since the color of stool is dependent both upon what we eat and what we use to digest food.
What can your poo tell you? Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email.