Grit and Gizzards – how birds digest seeds


Seed-eating birds utilize a unique process in order to digest their hard-shelled diets. Digestive enzymes cannot penetrate the seed shells (for doves and other species that swallow the shells) nor, in some cases, the inner seed covering (species that crack seeds before eating). To get around this, birds have evolved a muscular organ known as the gizzard, or ventriculus, to help grind their food into smaller pieces.

Seed-eating and certain other birds increase the gizzard’s effectiveness by swallowing stones and gravel, which are stored and act as grinding surfaces. These stones are periodically regurgitated or passed in the feces, possibly to prevent their becoming smooth and, consequently, less effective. Be sure to always have grit available to your seed-eating birds, prod or they will not be able to derive adequate nutrition from even a well-planned diet. Bits of cuttlebone also help to grind seeds, but only temporarily.

Pigeons swallow huge amounts of gravel, as they consume their seeds shell and all. While working with reptiles years ago at the Bronx Zoo, it was standard practice to trap pigeons for use as crocodile food (sorry, pigeon fanciers – I like pigeons too, but it was impossible to keep them out of certain exhibits, and they were implicated in the spread of diseases to the collection and staff). However, tests showed that the pigeons’ lead levels were incredibly high, due in part to ingesting the heavily-polluted Bronx gravel, and we ceased the practice (the pigeons were and remain fat and healthy none-the-less).

In the Bronx community where I grew up, “city” pigeons featured in the diets of people from several European countries. Elderly but quick-handed women tossed wet towels over pigeons as they came to feed on fire escapes (on bread put out by the same women, of course!) and knocked the squabs from nests with long bamboo canes. I never protested, despite my interest in all things avian, as their quick reflexes were just as likely to be used against annoying children as tasty pigeons! Well, that neighborhood is still home to some quite elderly people, so perhaps the lead-laced pigeons have not had their revenge!

A number of fishes and crocodilians have gizzards and utilize stones – more on that in the future.

Diagnosis and Treatment of Ailments Afflicting Parrots, Canaries, Finches, Mynas and other Cage and Aviary Birds – Part 2

Click here to read the first part of this article.

Foot Ailments

Bumblefoot (swollen toe joints)

Bacterial infections (often Staphylococcus) take hold in small wounds on the feet (received from splinters, glass, frostbite, etc.) especially if droppings have been allowed to accumulate.

Prompt antibiotic treatment is necessary if surgery is to be avoided; if left untreated, gangrene will set in, resulting in loss of the foot.

Calluses (thick, hard pads on bottom of feet)

Can result from perching on perches that are too hard, or that do not vary in width.

Be sure main (roosting) perch is of a width that allows toes to extend ¾ of the way around. Other perches should be of varying widths and materials; including A & E Rope and Cable Perches and similar perches allow the bird to choose a soft surface on occasion. Concrete perches should not be used as main perch but rather only as accessory perches, i.e. near the food bowl (and not at all if calluses are present).

Feather Ailments

French Moult (damaged feathers, loss of flight and tail feathers, bleeding)

Caused by a viral infection (Polyomavirus), French moult usually afflicts young parrots. It is rarely fatal but bird may be unable to fly thereafter.

There is no known treatment; recovered birds may still harbor the virus and thus should not be bred.

Feather Cysts (small lumps on the feathers)

Most common in canaries, this condition is genetic and the result of inbreeding.

Incurable; care should be taken to avoid breeding related birds or related lined of birds to each other.

Respiratory Ailments

Tracheal Mites and Gape Worm (wheezing, difficulty breathing, gaping, coughing, voice change/loss)

The parasites responsible for these conditions may be spread by other birds (in the case of mites) or through foods, such as earthworms, that may harbor gape worms.

Ivermectin and other anti-parasite medications are effective treatments. Infected birds should be isolated from others.

Psittacosis (fluid dripping from nostrils, breathing difficulty, exhaustion, inflamed eyes, sometimes accompanied by diarrhea)

This bacterial (Clamydia) disease is readily transmittable to people and can be fatal.

Contact your family doctor and veterinarian immediately.

Digestive Ailments

Salmonella Infection (huddled posture, diarrhea, stained vent feathers, lethargy)

This bacterium can be spread by roaches, rodents, wild birds, infected pet birds and seed contaminated with rodent droppings, and is most common among birds kept in unclean and crowded situations.

Salmonella is readily transmitted to people, and may be fatal to very young, elderly or immune-compromised individuals. Veterinarian-administered antibiotic treatments are often effective.

Candidiasis (mouth open and tongue extended; white fungus may appear along inner surfaces of the bill)

This fungal disease usually occurs in the presence of Vitamin A deficiencies, and is most commonly seen in nectar feeding birds (lories, hummingbirds, sunbirds).

Antibiotics and Vitamin A supplements are usually effective.

Reproductive System Ailments

Egg Binding (swelling about vent, straining, labored breathing, sitting on floor, puffed feathers)

The inability of a female bird to pass an egg is usually the result of a calcium deficiency.

Although lubricants applied to the cloaca (vent) sometimes help, veterinary intervention is usually required. A well-balanced diet that includes the correct amounts of calcium and other minerals is particularly important for females of all species.

Cloacal Warts or Papillomas (small, hard growths on and about the cloaca, or vent)
Cloacal warts are most commonly seen in South American parrots, particularly Amazons and macaws. They may constrict the cloaca, causing constipation and preventing the bird from breeding.

Silver nitrate (bathing the affected area) cures the condition, but afflicted birds should not be allowed to breed until they have been wart-free for at least 1 year.

Information concerning commonly encountered ailments (parakeets and related species) is posted at:


Diagnosis and Treatment of Ailments Afflicting Parrots, Canaries, Finches, Mynas and other Cage and Aviary Birds – Part 1

As with all pets, a nutritious diet and proper environmental conditions are the most important factors in maintaining the health of captive birds. When health concerns do arise, you should seek veterinary assistance. The following information will help you to identify, avoid and treat (while awaiting a veterinarian’s advice) commonly encountered bird ailments. It is a good idea to always have on hand a basic first aid kit, such as the VSI Pet Care Kit

Please remember that many bird-borne illnesses are transmittable to people, where they can cause severe or even fatal reactions. Consult your doctor concerning appropriate preventative steps, even if your bird is healthy. Emerging diseases, such as Avian Flu and West Nile Virus, should also be discussed.

A Word about Stress
After working with hundreds of bird species over several decades, I can say with certainty that stress is one of the most important underlying factors affecting the health of captive birds. This applies to a greater or lesser extent to different species and individual birds, but it is of concern to all.

Unfortunately, the problems caused by stress often manifest themselves in ways that seem unrelated to stress, and so we may wind up treating an illness but neglecting its underlying cause. For example, the fungus Aspergillus is common in nearly all environments and causes healthy birds no trouble at all. Years ago, however, bird keepers noticed that birds of many species became ill with Aspergillus infections (Aspergillosus) when moved from one cage to another. Samples taken in zoos showed that this occurred despite the fact that fungus levels were the same in both cages.

The explanation is that the transfer of a bird from its usual home to another is an extremely stressful event, especially for secretive species (i.e. birds of paradise in zoos, or certain finches in the pet trade) or shy individuals. The stress weakens the bird’s immune system, and pathogens that were otherwise destroyed by it now render the bird ill. So common is this phenomenon that many zoos now routinely medicate birds before moving them to new exhibits.

Immune system stress can arise from other factors as well – threatening cage mates, noise, poor diet, inappropriate temperatures, boredom and so on. Be sure to learn as much as you can about your pets, and provide them with the proper captive environment.

Eye Ailments

Red, swollen or closed eyes are indicative of an infection or traumatic injury. Please be aware that such is also seen in birds infected with Psittacosis, a serious disease that is transmittable to people.

Apply an ophthalmic ointment or drop (drops are often washed away by the eye’s secretions). Be sure to keep the cage bars and perches clean, as birds often rub sore eyes on these.

Check back on Wednesday for the conclusion of this article.

The Role of Learning and Instinct in Bird Song – lessons from the Zebra Finch, Taeniopygia guttata – Part 2

Zebra Finch

Click here to read the first part of this article
Song Recognition
It seems that song recognition, on the other hand, is instinctive – female birds of all species tested respond (with an increased heart rate!) to the songs of males of the same species. Male birds of the same species, but living in different places, develop local “dialects” – similar, perhaps, to the differences between the accents of people raised in NYC and Dallas. Female birds usually recognize the song of any male of their species, but respond with increased interest (again, the heartbeats) to songs from “neighborhood” males (sorry, I do not know if any conclusions pertaining to people can be drawn!).

Zebra Finches in the Wild
We are so accustomed to seeing zebra finches in cages that it is easy to overlook their existence as vital members of a natural environment. However, free-living zebra finches are perhaps the most abundant birds in the interior of their native Australia. With the exception of coastal Victoria and New South Wales, they inhabit the entire continent. In fact, their range is expanding due to the provision of water (they must drink daily) on livestock farms. A subspecies of the zebra finch (which was actually the first member of the species to be brought into captivity), the Lesser Sunda zebra finch, occupies nearby Timor and the Lesser Sunda Islands.

Despite their common name, zebra finches are not true finches but rather are classified as waxbills, in the family Estrildidae. Nearly 150 species of waxbills range throughout Africa, Asia and Australia. A number of the zebra finch’s relatives, including the gouldian finch, the cordon blue and the white-backed munia, are also popular in the pet trade. The nearly 200 species of true finches (family Fringillidae) are absent from Australia.

Habitat and Adaptations
Zebra finches favor open woodlands, grasslands and farms, but can also be found in Australia’s harsh, arid interior scrublands. They feed mainly upon seeds, especially those of various grasses, and take insects as well. Populations living in salt marshes have evolved the ability to drink salt water – excreting excess sodium via the kidneys. They are fairly sensitive to temperature and cannot generate enough heat for egg incubation if temperatures fall below 53 F.

Like many of its relatives, the zebra finch forages in large flocks. Within the flock, however, monogamous pairs form. The pair bond appears, in most cases, to be life-long. Breeding is sporadic throughout the year and may not occur at all during droughts. As an adaptation to the harsh environment, this species has evolved the ability to breed quickly at the onset of rains during nearly any time of the year.

Zebra finches nest as discrete pairs, but communally – that is, with many pairs occupying the same tree. The female chooses the nest site and constructs the nest with dried grasses and other materials brought by the male. The 4-5 eggs are incubated by both parents and hatch in 13-16 days. The young, fed by the male and female, fledge in 20-21 days. In years with favorable rainfall and food supplies, 3 or more broods may be raised. The zebra finch’s ability to take advantage of good conditions can be a handicap in captivity – in response to the abundance of food and water, females may lay so often that their health suffers (this problem can be ameliorated somewhat by removing all nesting material).

A View from Taiwan
As mentioned earlier, zebra finches are popular pets, both here and abroad. A Taiwanese friend has informed me that they are much more “house pet” than “cage bird” in her country, and are commonly allowed to roam about. Her pet zebra finch would perch on a chair while the family ate dinner – begging for food but not actually approaching the table, and would sleep in her shirt pocket in the evening.


Further information on the parallels between zebra finch song the acquisition of speech in people is available at:

The Role of Learning and Instinct in Bird Song – lessons from the Zebra Finch, Taeniopygia guttata – Part 1

Zebra Finch

Have you ever wondered, upon hearing a pet canary or wild mockingbird sing, just how it is that birds acquire such complex abilities – are they born songsters, or must they learn? Well, scientists at the Massachusetts Institute of Technology (MIT) have, and the zebra finch has provided some answers. In doing so, this species, long used in human neuroscience and other health related research (so much so that is often termed the “mouse of the avian world”), has also shed some light on speech development in humans.

The Role of the Brain
Although birds are linked in our minds, to song, only a very small percentage of the world’s 10,000+ species – those classified within the suborder Oscines – actually sing (and the voices of some of these, such as the crow, stretch the definition of “song”!). Baby zebra finches, much like human babies, babble on with an infinite variety of noises – practicing until they eventually learn the adult song. Once learned, the song is never varied.

Research completed last month (May, 2008) at MIT has revealed that two distinct brain pathways are involved – one for learning the song, the other for producing (singing) what has been learned. Damage to the learning pathway of a young finch prevents it from ever producing the adult song, but the same damage during adulthood has no effect on the bird’s singing abilities.

Bird Song and Human Speech
The MIT researchers have drawn some parallels to human learning abilities that bear further investigation. In zebra finches, the youngster’s vocal explorations cease once the adult song has been acquired, as the song never changes. However, the learning pathway is retained, possibly as a back-up system – damage to the song-producing pathway of an adult causes the bird to revert to sounds produced during the learning phase. We humans rely greatly on learning abilities, or pathways, throughout our lives, yet certain aspects of speaking, such as our ability to learn a language without an accent, must occur during childhood. So perhaps we also utilize, at least to some extent, two separate brain pathways when learning and producing sound.

Instinct and Mimicry
In all birds there seems to be an instinctive “song framework” that is filled in by learning and mimicry – male birds raised in isolation develop only incomplete songs that are not recognized by others of their species. The specifics of how the various popular pet birds learn their songs vary from species to species. Baby zebra finches pay attention only to the song of the male that actually feeds them. For example, zebra finches incubated (in captivity) by Bengalese finches grow up to sing the song of their foster parents – this despite the fact that the nestlings could hear other zebra finches singing nearby! How they know which song to choose among the many they hear is not yet understood.

The pet birds most valued for their singing abilities, such as canaries and shama thrushes, copy a wide variety of songs, not only those typical of their species. Indeed, owners of these birds can improve their pets’ vocal repertoires by exposing them to “tutor birds” of the same or different species. A favorite story among canary fanciers is that of a canary which learned to whistle the melody to “God Save the King” by listening to a trained bullfinch do the same in an adjoining room……if the bullfinch hesitated too long while singing, the canary would jump in and finish the melody at exactly the right point!

Check back on Friday for the rest of this article.
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