Reptile Care

Reptile Classification

Dog's Digestive System
Unlike Birds and Mammals, their kidneys cannot produce liquid urine with higher concentration than the body fluids. This means separating the ones that are morphing into a beetle, as the other will eat them. On the other hand, the three-chambered hearts in various lizard and snake species can function as the four-chambered ones during contraction. Digestion in bats is unusually rapid. July 15, at I know I have to go with a low fat, high fiber food mix. John Wiley and Sons Inc.

More about Amphibians & Reptiles:

Amphibians & Reptiles

In all reptiles the urinogenital ducts and the anus both empty into an organ called a cloaca. In some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all. It is present in all turtles and tortoises as well as most lizards, but is lacking in the monitor lizard , the legless lizards. It is absent in the snakes, alligators, and crocodiles. Many turtles, tortoises, and lizards have proportionally very large bladders.

Turtles have two or more accessory urinary bladders, located lateral to the neck of the urinary bladder and dorsal to the pubis, occupying a significant portion of their body cavity. The right section is located under the liver, which prevents large stones from remaining in that side while the left section is more likely to have calculi. Most reptiles are insectivorous or carnivorous and have simple and comparatively short digestive tracts due to meat being fairly simple to break down and digest.

Digestion is slower than in mammals , reflecting their lower resting metabolism and their inability to divide and masticate their food. While modern reptiles are predominantly carnivorous, during the early history of reptiles several groups produced some herbivorous megafauna: Herbivorous reptiles face the same problems of mastication as herbivorous mammals but, lacking the complex teeth of mammals, many species swallow rocks and pebbles so called gastroliths to aid in digestion: The rocks are washed around in the stomach, helping to grind up plant matter.

The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger.

Most typical sense organs are well developed with certain exceptions, most notably the snake 's lack of external ears middle and inner ears are present. There are twelve pairs of cranial nerves. Reptiles are generally considered less intelligent than mammals and birds. Larger lizards, like the monitors , are known to exhibit complex behavior, including cooperation. The Komodo dragon is even known to engage in play, [] as are turtles, which are also considered to be social creatures, [ citation needed ] and sometimes switch between monogamy and promiscuity in their sexual behavior.

Most reptiles are diurnal animals. The vision is typically adapted to daylight conditions, with color vision and more advanced visual depth perception than in amphibians and most mammals. In some species, such as blind snakes , vision is reduced. Some snakes have extra sets of visual organs in the loosest sense of the word in the form of pits sensitive to infrared radiation heat.

Such heat-sensitive pits are particularly well developed in the pit vipers , but are also found in boas and pythons. These pits allow the snakes to sense the body heat of birds and mammals, enabling pit vipers to hunt rodents in the dark.

Reptiles generally reproduce sexually , though some are capable of asexual reproduction. Most reptiles have copulatory organs , which are usually retracted or inverted and stored inside the body. In turtles and crocodilians, the male has a single median penis , while squamates, including snakes and lizards, possess a pair of hemipenes , only one of which is typically used in each session. Tuatara, however, lack copulatory organs, and so the male and female simply press their cloacas together as the male discharges sperm.

Most reptiles lay amniotic eggs covered with leathery or calcareous shells. An amnion , chorion , and allantois are present during embryonic life. The eggshell 1 protects the crocodile embryo 11 and keeps it from drying out, but it is flexible to allow gas exchange. The chorion 6 aids in gas exchange between the inside and outside of the egg. It allows carbon dioxide to exit the egg and oxygen gas to enter the egg.

The albumin 9 further protects the embryo and serves as a reservoir for water and protein. The allantois 8 is a sac that collects the metabolic waste produced by the embryo. The amniotic sac 10 contains amniotic fluid 12 which protects and cushions the embryo. The amnion 5 aids in osmoregulation and serves as a saltwater reservoir. The yolk sac 2 surrounding the yolk 3 contains protein and fat rich nutrients that are absorbed by the embryo via vessels 4 that allow the embryo to grow and metabolize.

The air space 7 provides the embryo with oxygen while it is hatching. This ensures that the embryo will not suffocate while it is hatching. There are no larval stages of development. Viviparity and ovoviviparity have evolved in many extinct clades of reptiles and in squamates. In the latter group, many species, including all boas and most vipers, utilize this mode of reproduction.

The degree of viviparity varies; some species simply retain the eggs until just before hatching, others provide maternal nourishment to supplement the yolk, and yet others lack any yolk and provide all nutrients via a structure similar to the mammalian placenta. The earliest documented case of viviparity in reptiles is the Early Permian mesosaurs , [] although some individuals or taxa in that clade may also have been oviparous because a putative isolated egg has also been found.

Several groups of Mesozoic marine reptiles also exhibited viviparity, such as mosasaurs , ichthyosaurs , and Sauropterygia , a group that include pachypleurosaurs and Plesiosauria. Asexual reproduction has been identified in squamates in six families of lizards and one snake.

In some species of squamates, a population of females is able to produce a unisexual diploid clone of the mother. This form of asexual reproduction, called parthenogenesis , occurs in several species of gecko , and is particularly widespread in the teiids especially Aspidocelis and lacertids Lacerta. In captivity, Komodo dragons Varanidae have reproduced by parthenogenesis. Parthenogenetic species are suspected to occur among chameleons , agamids , xantusiids , and typhlopids.

Some reptiles exhibit temperature-dependent sex determination TDSD , in which the incubation temperature determines whether a particular egg hatches as male or female.

TDSD is most common in turtles and crocodiles, but also occurs in lizards and tuatara. Many small reptiles, such as snakes and lizards that live on the ground or in the water, are vulnerable to being preyed on by all kinds of carnivorous animals. Thus avoidance is the most common form of defense in reptiles. Reptiles tend to avoid confrontation through camouflage. Two major groups of reptile predators are birds and other reptiles, both of which have well developed color vision.

Thus the skins of many reptiles have cryptic coloration of plain or mottled gray, green, and brown to allow them to blend into the background of their natural environment. When camouflage fails to protect them, blue-tongued skinks will try to ward off attackers by displaying their blue tongues, and the frill-necked lizard will display its brightly colored frill.

These same displays are used in territorial disputes and during courtship. Rattlesnakes rapidly vibrate the tip of the tail, which is composed of a series of nested, hollow beads to ward of approaching danger.

In contrast to the normal drab coloration of most reptiles, the lizards of the genus Heloderma the Gila monster and the beaded lizard and many of the coral snakes have high-contrast warning coloration, warning potential predators they are venomous.

Camouflage does not always fool a predator. When caught out, snake species adopt different defensive tactics and use a complicated set of behaviors when attacked. Some first elevate their head and spread out the skin of their neck in an effort to look large and threatening.

Failure of this strategy may lead to other measures practiced particularly by cobras, vipers, and closely related species, which use venom to attack. The venom is modified saliva, delivered through fangs from a venom gland. When a crocodilian is concerned about its safety, it will gape to expose the teeth and yellow tongue.

If this doesn't work, the crocodilian gets a little more agitated and typically begins to make hissing sounds. After this, the crocodilian will start to change its posture dramatically to make itself look more intimidating. The body is inflated to increase apparent size. If absolutely necessary it may decide to attack an enemy. Some species try to bite immediately. Some will use their heads as sledgehammers and literally smash an opponent, some will rush or swim toward the threat from a distance, even chasing the opponent onto land or galloping after it.

Many species also possess canine -like teeth. These are used primarily for seizing prey, but are also used in fighting and display. Geckos , skinks , and other lizards that are captured by the tail will shed part of the tail structure through a process called autotomy and thus be able to flee.

The detached tail will continue to wiggle, creating a deceptive sense of continued struggle and distracting the predator's attention from the fleeing prey animal. The detached tails of leopard geckos can wiggle for up to 20 minutes. In the shingleback skink and some species of geckos, the tail is short and broad and resembles the head, so that the predators may attack it rather than the more vulnerable front part. Reptiles that are capable of shedding their tails can partially regenerate them over a period of weeks.

The new section will however contain cartilage rather than bone, and will never grow to the same length as the original tail. It is often also distinctly discolored compared to the rest of the body and may lack some of the external sculpting features seen in the original tail. Dinosaurs have been widely depicted in culture since the English palaeontologist Richard Owen coined the name dinosaur in As soon as , the Crystal Palace Dinosaurs were on display to the public in south London.

The depictions range from the realistic, as in the television documentaries of the s and first decade of the 21st century, or the fantastic, as in the monster movies of the s and s. The snake or serpent has played a powerful symbolic role in different cultures. In Egyptian history , the Nile cobra adorned the crown of the pharaoh.

It was worshipped as one of the gods and was also used for sinister purposes: In Greek mythology snakes are associated with deadly antagonists, as a chthonic symbol, roughly translated as earthbound.

The nine-headed Lernaean Hydra that Hercules defeated and the three Gorgon sisters are children of Gaia , the earth. Medusa was one of the three Gorgon sisters who Perseus defeated.

Medusa is described as a hideous mortal, with snakes instead of hair and the power to turn men to stone with her gaze. After killing her, Perseus gave her head to Athena who fixed it to her shield called the Aegis. The Titans are depicted in art with their legs replaced by bodies of snakes for the same reason: They are children of Gaia, so they are bound to the earth. The cobra is seen on the neck of Shiva , while Vishnu is depicted often as sleeping on a seven-headed snake or within the coils of a serpent.

There are temples in India solely for cobras sometimes called Nagraj King of Snakes , and it is believed that snakes are symbols of fertility. In the annual Hindu festival of Nag Panchami , snakes are venerated and prayed to. The turtle has a prominent position as a symbol of steadfastness and tranquility in religion, mythology, and folklore from around the world.

Deaths from snakebites are uncommon in many parts of the world, but are still counted in tens of thousands per year in India. To produce antivenom, a mixture of the venoms of different species of snake is injected into the body of a horse in ever-increasing dosages until the horse is immunized. Blood is then extracted; the serum is separated, purified and freeze-dried. Geckos have also been used as medicine, especially in China.

Crocodiles are protected in many parts of the world, and are farmed commercially. Their hides are tanned and used to make leather goods such as shoes and handbags ; crocodile meat is also considered a delicacy. Farming has resulted in an increase in the saltwater crocodile population in Australia , as eggs are usually harvested from the wild, so landowners have an incentive to conserve their habitat.

Crocodile leather is made into wallets, briefcases, purses, handbags, belts, hats, and shoes. Crocodile oil has been used for various purposes.

In the Western world, some snakes especially docile species such as the ball python and corn snake are kept as pets. From Wikipedia, the free encyclopedia. This is the latest accepted revision , reviewed on 14 August For other uses, see Reptile disambiguation. List of reptiles and List of snakes. Venom and Evolution of snake venom. Evolution of the Vertebrates 2nd ed.

John Wiley and Sons Inc. Journal of Experimental Biology. Laurin, Michel and Gauthier, Jacques A.: Lizards Windows to the Evolution of Diversity. University of California Press. The Phylogeny and Classification of the Tetrapods. Zoological Journal of the Linnean Society. Retrieved 4 February The University of Chicago Press.

Systema naturae per regna tria naturae: Retrieved September 22, Nouveau Dictionnaire à Histoire Naturelle, xxiv. The Structure and Classification of the Mammalia. Hunterian lectures, presented in Medical Times and Gazette, Proceedings of the Royal Society of London B. The Royal Natural History: Retrieved March 25, The Variety of Life.

Memoirs of the American Museum of Natural History. Once we determine that you have a valid claim, we will replace the DOA feeders with your next order. Under no circumstances is The Worm Lady able to refund payment, and the buyer is responsible for any and all shipping charges associated with the replacements.

There is no point at all in spending money on insects and worms that have not themselves received appropriate nutrition. Feed as many different healthy things as you can find see: Buy live feeders, worms and crickets, that are already 'gut loaded' and full of moisture and nutrients.

What do reptiles eat? There is a huge difference between feeding When you buy your live feeders ask yourself I"m talking about proper, 'feeder-specific' nutrition. At The Worm Lady we ensure that everything we ship has been raised with fresh, nutritious chow and that they receive adequate moisture every day. Their substrate what they live in and eat is cleaned regularly. There is NO overcrowding and we ensure optimal ventilation for healthy insects.

It is a fact that improperly kept and improperly fed live feeders result in poor nutritional quality, and can even cause illness for your pets and added expense for you. We always ship your order of feeders with a little food for the voyage. It is our aim to deliver to you top quality live feeders at an excellent price, and to always follow through with prompt and courteous customer service. Further down below we've listed and described our live feeders in order of nutrition - with the best being number one - the lowest number 8, and trust that this will help you in making wise decisions when you are buying live feeders for your reptiles,.

If along with your regular order you're only wanting to try one or two horn worms, or silkworms, or a dozen 'BSFL', please, just let us know.

P ratio see the description. NO need to dust your other feeder insects when this is the staple diet. Iron-Clad Live delivery guaranteed regardless of the destination weather conditions. The larvae have voracious appetites and can be used for composting household food scraps and agricultural waste products in warm climates of 80F F.

Black soldier fly larvae BSFL are an excellent source of sustainable protein for aqua culture, animal feed, pet and human nutrition. They are truly a Maintenance-Free grub and can last weeks in the larva stage when kept dormant at F. I want to send a big thank-you for your service and quality of dew worms we received from you mid-July.

Our fishing trip was so successful because of how lively and fresh the worms were. The rest of the camp was jealous of our quantity and shape of our worms. Trout Worms Fishing Bait.

Many people believe that there is no such thing as too much calcium in a reptile's diet, especially, when it is through supplementation.

This is definitely not true. Calcium in high doses can act as a binder, which inhibits the absorption of essential nutrients such as other essential minerals, as well as vitamins. In the presence of too much Vitamin D, excess Calcium can calcify the internal organs, liver and kidneys. Calcium neutralizes stomach acids, which are necessary for the digestion and absorption of all nutrients. Many drugs have warnings to not take them with an antacid because it can prevent the drug from being absorbed into the system.

Giving a large dose of calcium all at once is not the same as giving a smaller amount with every second feeding.

It's generally agreed across the vertebrate world, that an inclusion ratio of 2: This is a common ratio measured in healthy bone analysis of most vertebrates including humans.

To err to the high side with calcium is generally much easier to metabolize than a diet that has less than a 2: Feed a Silkworm times week to provide a balanced diet. More Calcium and Hydration requirements information continued below on this page Bubba having her lunch of 28 worms: When temperatures are lower then 7 C, or higher than 25 C we may elect to wait to ship until temperatures return the the Safe-Zone.

If you still want your order shipped using a slower service 2 or more days there is NO Live Delivery Guarantee - your are assuming the risk of DOA grubs and we assume no liability whatsoever for any dead insects. Wed, Apr 29, at Almost no DOA, lasted, without mysteriously dying off, for weeks and any that did were likely due to me not knowing how to keep them alive properly - yet!

And my Beardie and Geckos loved them! I need another shipment. Really, compared to the big box pet stores, and even the specialty ones I tried here in Toronto, The Worm Lady is far superior. I have sent the funds by email. Annie relaxing with princess Cleopatra Please note that your order will ship Canada Post Overnight Next-Day only when temperatures are forecast to stay around 44 F 7 C for a minimum of 2 consecutive days We compost all our organic waste for use in our organic vegetable garden and flower beds.

We also raise our Live Feeders on organic live foods. This is your assurance that you are getting the healthiest and the best quality live feeders for your pets - and our small contribution in the preservation of our local eco-system.

Sunday July 20, - 9: Absolute Essentials for healthy herps When you order your live feeders from me I always do my absolute best to ensure an over-count, prompt next-day delivery - whenever possible, proper and personal attention to each order, and well-fed, healthy live feeders to you - my customers.

Excellent nutrition and responsible husbandry must be combined to ensure the health of your reptiles. You can be feeding the most perfectly balanced diet in existence, but without the optimum temperature gradient, that 'perfect diet' is not able to be properly digested. Reptiles are cold blooded animals so they require heat in order to digest their foods. If this temperature requirement is not met the food will simply rot in their gut and not be digested, resulting in elevated uric acid levels, and an acidic blood pH level causing detrimental damage to your reptile.

Digestion is not only impaired by improper heat requirements, but lack of hydration can also have adverse effects on digestion as well. Water consumption is often overlooked when thinking about digestion, but without proper amounts of water intake the process of digestion can be halted , thus, causing serious damage to your reptiles.

If you have a picky eater who will not eat a good variety of live feeders for a properly balanced diet you should try some of the Repashy Superfoods Meal Replacement products. These were scientifically formulated to return your pet to optimum health, and keep him healthy for the long term too! Organically Raised Live Feeders: Our beardies love being out and about so we take them with us everywhere we go The order did arrive the next day and was in perfect condition.

I would like another Phoenix worms and 20 silkworms. Saturday August 2, - Anyway - getting back to hydration: An example of water intake is through the ingestion of insects. Insects alone can provide a large amount of water to aid in the hydration of your reptile.

In their natural habitat the early morning dew that is apparent in many arid lands is yet another method of water consumption, and for the herbivores, they will get much of their hydration from consuming plant material. Although not part of the digestive system in an anatomical sense, some birds, like hawks and owls , use their feet and talons to capture prey. Typically, raptor prey are killed by the talons of the contracting foot being driven into their bodies; if required, the hooked bill is used to kill prey being held by the talons.

The raptor digital tendon locking mechanism -- Digital tendons form a mechanical-locking mechanism in many birds that must maintain a degree of grip force, including perching, hanging, tree-climbing, and raptorial species. In raptors, powerful hindlimb muscles produce a strong grasp, and a tendon locking mechanism TLM helps sustain grip force.

The components of the digital TLM include a 'textured' pad on the ventral surface of each flexor tendon that contains thousands of minute, rigid, well-defined projections called tubercles see figure below.

The neighboring portion of the surrounding tendon sheath contains a series of transversely running plicae folds that often have a proximal slant i. When the flexor tendons are pulled taut, and the digits flexed, the tubercle pad moves proximally over the stationary plicae on the sheath. When resistance to digital flexion is met, the locking elements intermesh and engage and the friction produced prevents slippage of the tendons.

This permits digital flexion to be maintained with little or no muscular involvement E inoder and Richardson Action of the avian digital TLM: This shows the movement of the talon a , flexor e and extensor d tendons, ungual phalanx b , and the movement of the ventrally located tubercle pad f relative to the stationary plicated sheath g and phalangeal bone c From: Einoder and Richardson Each raptor has a unique force production, along with a different time of activity, that would allow for a degree of prey specialization.

Great Horned Owl foot. B Great Horned Owl. The relation between rate of success and direction of movement for a food item that was pulled forward a , backward b and sideways c. Direction of prey progression — dotted arrow 1 , direction of owl flight — dashed arrow 2 , and direction to which the owl had to move its head or trunk — solid arrow 3.

Owl picture from Knudsen Movement and direction of prey affect raptor success rate -- Shifferman and Eilam tested a novel idea, that rather than maximizing their distance from a predator during close-distance encounters, prey species are better off moving directly or diagonally toward the predator in order to increase the relative speed and confine the attack to a single available clashing point.

They used two tamed Barn Owls Tyto alba to measure the rate of attack success in relation to the direction of prey movement. A dead mouse or chick was used to simulate the prey, pulled to various directions by means of a transparent string during the owl's attack.

This failure to catch prey that move sideways may reflect constraints in postural head movements in aerial raptors that cannot move the eyes but rather move the entire head in tracking prey. So far there is no evidence that defensive behavior in terrestrial prey species takes advantage of the above escape directions to lower rates of predator success. However, birds seem to adjust their defensive tactics in the vertical domain by taking-off at a steep angle, thus moving diagonally toward the direction of an approaching aerial predator.

These preliminary findings warrant further studies in Barn Owls and other predators, in both field and laboratory settings, to uncover fine predator head movements during hunting, the corresponding defensive behavior of the prey, and the adaptive significance of these behaviors. Barred Owl primary - leading edge below and trailing edge above.

The silent flight of owls -- Noise is generated by vortices produced when air flows over a bird's wing and larger vortices produce more noise. Wings with small saw-toothed projections vortex generators , like those on the leading edge of owl wings, generate many small vortices instead of large vortices and produces less aerodynamic noise. In addition, the fringe feathers at the trailing edge of the wing with fewer hooklets at the ends of the barbs help to break up the sound waves that are generated as air flows over the top of their wings and forms downstream wakes, and the soft down feathers located elsewhere on the wings and legs of owls absorb the remaining sound frequencies above 2, hertz and make owls completely silent to their prey.

As a bonus, with high angles of attack and at slow speeds, vortex generators stick out of the stagnant air near the surface of the wing, and into the freely moving air outside the boundary layer.

This surface layer is typically quite thin, but dramatically reduces speed of the airflow towards the rear of the wing. The vortex generators mix the free stream with the stagnant air to get it moving again, providing considerably more airflow at the rear of the wing and helping to prevent stalling. This process is referred to as 're-energizing the boundary layer. Unpredictable predators -- The use of space by predators in relation to their prey is a poorly understood aspect of predator-prey interactions.

Classic theory suggests that predators should focus their efforts on areas of abundant prey, that is, prey hotspots, whereas game-theoretical models of predator and prey movement suggest that the distribution of predators should match that of their prey's resources.

If, however, prey are spatially anchored to one location and these prey have particularly strong antipredator responses that make them difficult to capture with frequent attacks, then predators may be forced to adopt alternative movement strategies to hunt behaviorally responsive prey.

Roth and Lima examined the movement patterns of bird-eating Sharp-shinned Hawks Accipiter striatus in an attempt to shed light on hotspot use by predators. Their results suggest that these hawks do not focus on prey hotspots such as bird feeders but instead maintain much spatial and temporal unpredictability in their movements.

Hawks seldom revisited the same area, and the few frequently used areas were revisited in a manner consistent with unpredictable returns, giving prey little additional information about risk.

But why wouldn't Sharp-shinned Hawks focus their hunting on the areas with the most potential prey bird feeders? One possibility is that behaviorally responsive prey diminish the "hotspot" quality of feeders.

Although feeder hotspots are sources of abundant prey, the individuals at such feeders generally benefit from group vigilance as a result of these higher densities. As a result, the vulnerability of the prey may actually be lower at feeders than at other locations.

In addition, unpredictable movement may reflect a sort of "prey management" by predators, whereby predators spread their hunting activity over multiple areas in an effort to avoid inflating the antipredator behavior of their prey. This hunting strategy may be effective when prey are anchored to high-resource areas such as feeders and use antipredator behaviors, such as high vigilance, that reduce a predator's attack success if it attacks frequently and predictably.

Seabirds are choking on ocean plastic video. The tongues of cormorants and other fish-eating species are small because these species swallow prey whole and tongues are not needed to manipulate or position food in the oral cavity.

Dorsal view of the surface of the lower bill of a Great Cormorant Phalacrocorax carbo. Arrow shows the tongue with sharpened tip. Scale bar, 12 mm. Lateral view of the cormorant tongue. The tongue and the small anterior and posterior areas of the mucosa of the bill are covered by white keratinized epithelium. Black arrow shows short base of the tongue. White arrow shows the median crest on the dorsal surface of the tongue. A, anterior; B, posterior. Scale bar, 3 mm Source: Detailed view of the horny tip left of the Guadeloupe Woodpecker tongue in vivo position Villard and Cuisin Dorsal view of the tongue of the Spotted Nutcracker Nucifraga caryocatactes.

Arrows show two elongated processes of the apex. A, apex, B, body, R, root, LP, laryngeal prominence. Scale bar, 3 mm. Lateral view of the tongue of the nutcracker. Arrow shows elongated processes, pointed diagonally, B, body, R, root. Hummingbird tongues are fluid traps, not capillary tubes -- Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics.

Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. Rico-Guevara and Rubega found that hummingbird tongues do not function like a pair of tiny, static tubes drawing up floral nectar via capillary action.

Instead, the tongue tip is a dynamic liquid-trapping device that dynamically traps nectar by rapidly changing their shape during feeding. In addition, the tongue—fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap. These results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds.

Hummingbird tongue tips twist to trap nectar. How the hummingbird tongue really works with videos. Close encounters with possible prey. You want to live 10—20 years. You are peering under leaves, poking into rolled ones, searching around stems, exploring bark crevices and other insect hiding places. Abruptly an eye appears, 1—5 cm from your bill.

The eye or a portion of it is half seen, obstructed, shadowed, partly out of focus, more or less round, multicolored, and perhaps moving. Now, a safe few meters away, are you going to go back to see whether that was food?

Associated body patterns often suggest other head and facial features, which in turn enhance the eye-like nature of the spots. None of these patterns exactly matches the eyes or face of any particular species of predator; but, even when quickly and partially glimpsed, all give the illusion of an eye or face. These false eyes are mimicking the eyes and faces of such predators of insect-eating birds as snakes, lizards, other birds, and small mammals, as perceived at close range by the insectivorous birds in their natural world.

Note the distended throat of this American Kestrel. Pigeons generally lay two eggs one day apart, which hatch 18 days after they are laid. A similar substance is produced by flamingos and male Emperor Penguins. The normal function of the crop is food storage. Pigeon 'milk' also contains IgA antibodies and antioxidants carotenoids.

The avian stomach is divided into 2 parts:. Photomicrograph 50X of a cross section through the proventriculus showing folds of mucous membrane P ; deep proventricular glands GP ; capsule connective tissue around the glands arrow head ; muscle layer m ; serosa connective tissue with blood vessels S , and the lumen L From: Photomicrograph X of longitudinal section of the gizzard showing folds of mucous membrane lined by simple prismatic epithelium P ; simple tubular glands Gs in the lamina propria constituted by connective tissue Lp ; secretion of glands S that are continuous with the cuticle or koilin ; C , part of muscle layer m , interpersed with bundles of connective tissue Tc From: Photomicrograph X of the koilin of an Eclectus Parrot Eclectus roratus.

Note the regular, columnated structure of the koilin layer K and its association with the glandular epithelium E of the ventriculus From: De Voe et al. A, koilin, B, crypts, C, glands that secrete koilin, D, epithelial surface, E, desquamated epithelial cells, 2 Mucosa of the gizzard.

A, koilin, B, secretion in gland lumens and crypts, and 3 Koilin layer. A, secretion column, B, koilin-layer surface, C, horizontal stripe indicating a 'pause' in secretion of the koilin, D, cellular debris. Eglitis and Knouff Vultures of the seas -- Animals are primarily limited by their capacity to acquire food, yet digestive performance also conditions energy acquisition, and ultimately fitness.

Optimal foraging theory predicts that organisms feeding on patchy resources should maximize their food loads within each patch, and should digest these loads quickly to minimize travelling costs between food patches. GPS-tracking of 40 Wandering Albatrosses from the Crozet archipelago during the incubation phase confirmed foraging movements of between — km, giving the birds access to a variety of prey, including fishery wastes.

Using miniaturized, autonomous data recorders placed in the stomach of three birds, the first-ever measurements of gastric pH and temperature in procellariformes were obtained.

Such low stomach pH gives Wandering Albatrosses a strategic advantage because it allows a rapid chemical breakdown of ingested food and rapid digestion. This is useful for feeding on patchy, natural prey, but also on fishery wastes, which might be an important additional food resource for Wandering Albatrosses. It is likely that this physiological characteristic evolved as a response to a diet largely composed of squid, and to a patchy distribution of this food resource resulting in large, infrequent meals.

The strategy of Wandering Albatrosses is to cover long distances rapidly and at low costs to increase the probability of encountering dispersed prey patches whose distribution is unpredictable. Knots with large gizzards consumed far more molluscs with shells than the birds with smaller gizzards. Birds with smaller gizzards simply couldn't feed fast enough. By allowing them to crush more shell per gizzard-full, larger gizzards gave birds the edge.

Thus, even though it is energetically costly for the knots to maintain a larger gizzard, when the bird needs to get the most out of its crunchy diet, it's a price worth paying. So, the birds' gizzards enlarge as they fatten for migration. Because the molluscs' shells stay the same size as the molluscs shrink, the amount of shell a bird must process to eat its fill also increases.

But with their larger gizzards, the birds can still make the most of even the crunchiest winter diet! Within 14 days, they showed a doubling of the size of their gizzards. Red Knots have strong muscular gizzards for feeding on molluscs.

A shift back to a mussel diet induced about a doubling in gizzard mass in just a few days. As the knots were fed progessively smaller mussels day 22 to day 46 that are easier to crush, gizzard mass again declined.

A switch back to a soft food pellet diet caused a further decline in gizzard mass. Finally, a switch back to a mussel diet again cause a rapid increase in gizzard mass From: Piersma and Drent Ostrich Struthio camelus stomach. Note how particle size of material in the gizzard ventriculus is smaller than in the proventriculus due to the grinding action of the muscular walls plus small pebbles gastroliths. The capacity to reduce particle size is related to the metabolic demands of a species.

Therefore, particle size reduction is often considered the key digestive difference between ecto- and endotherms that allows endotherms to rely on shorter digesta retention times without losing digestive efficiency, and hence facilitate the high level of food intake necessary to meet their increased metabolic requirements.

In contrast, adaptations for chewing intrinsically increase the weight of the head. 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.