By Dale R. Thompson

ICFB 1983

INTRODUCTION:
Significant advances have been made in the science of breeding psittacine birds during the past few decades. Of the approximately 330 species found in the wild, the majority have been kept in captivity and many of these have been bred. But the establishment of a population large enough to perpetuate a particular species in captivity has been rare. Also, these birds must be able to adapt to a captive environment to ensure their survival. This has been accomplished in only a few genera that include: the Budgerigar (Melopsittacus undulates), Cockatiel (Nymphicus hollandicus), some Lovebirds (Agapornis roseicollis and Agapornis personate) and the Indian R i ng neck (Psittacula krameri). As of of the beginning of the 1980’s, I believe that only about 25 species are reasonably close to being added to this list; they are included in the genera Neophema, Platycercus, Barnardius, Psephotus, Polytelis, Cyanoramphus and one species of Aratinga. This means that aviculturists have not understood the complete reproductive requirements for the majority of species. It is not that we are totally ignorant, for the majority of all psittacines kept in captivity have been reproduced at least on one occasion. It appears that the only guarantee of keeping psittacine birds in captivity indefinitely, is to make successful reproduction of all species our goal.

STRESS MANAGEMENT:
Stress is the single greatest deterrent to long-term captive reproduction of psittacine birds. A wild-caught bird is subjected to a wide variety of stressful situations from the time of capture to its arrival at its new home. Often inhumane methods of capture are used. Overcrowding is the norm; it exists at the time of capture, during transport and in quarantine stations. In addition, a bird must learn to adapt to a completely new diet, climatic changes and to the stress of human contact. Stress can cause medical problems to arise, such as illness and injury. Some birds appear to handle these stresses with relative ease, but most are affected very adversely, even though this may not be clearly noticeable at the time. There are additional stressful situations in captivity that can affect breeding. For instance, birds that are too confined or overcrowded can exhibit territorial behavior. Keeping stress minimal will enhance breeding in the long run.

CAPTIVE MANAGEMENT:
When birds are first acquired for a breeding program, a quarantine period is imperative; it reduces the risk of introducing disease into an established breeding facility. During this time every new bird should be tested for transmissible diseases, especially Psittacosis and Newcastle disease. Other tests may also be run to help evaluate the general health of the bird, such as tests for internal parasites and pathogenic bacteria. This could prevent serious problems from the outset.

Choosing birds that will become the best breeders can be difficult. Based on the author’s experience, the first choice would be a hand-reared bird that has not become imprinted on humans. When hand-raising birds that are to be used for future breeding, one would not isolate them from other birds and try to keep human contact other than that required for care to a minimum. After weaning, the young bird should be placed back with others of its own species as soon as it is possible. This type of bird is already acclimatized to the environment and will accept a broader variety of foods. The greatest advantage is that it is not as easily stressed around humans, unlike wild-caught birds. Even the most high-strung species are calm in the aviary if hand-reared. They will not run into walls if surprised and don’t hide in the nest box continually, as wild-caught birds, such as the Moluccan Cockatto (Cacatua moluccensis), are apt to do. After several years of observation it has been seen that hand-reared birds will breed sooner and more readily than those brought in from the wild.

Because the male bird is calmer, hand-raised parents produce a higher percentage of fertile eggs and these birds make better parents themselves. Obviously it is best to keep your own babies for breeding, or to purchase hand-raised young. These birds all-too-often end up in the pet trade and it is especially disheartening to see rare species being sold as pets.

If a hand-reared bird is not available, the next choice would be a bird reared in captivity by its parents. The off-spring of species difficult to breed usually shows a marked increase in their willingness to breed in captivity. This has been done for generations with most of the Australian parakeets, and is now being done with many of the larger species. However, many of the larger species may take a minimum of four years to become sexually mature, and the aviculturist must be willing to wait for this.

The third selection would be a wild-caught bird kept long enough in captivity to allow it to adjust to its new environment. We usually use birds that have been in captivity for years and often kept as pets. During the time it takes for the bird to adjust it will be approaching sexual maturity and its general condition can be evaluated.

After birds are selected for breeding, their sexes must be determined. Since most psittacine birds are not sexually dimorphic, often-unsuccessful attempts have been made to determine sex by beak differences, body size and behavioral characteristics. Several years ago veterinarians developed a surgical technique for sexing birds through a procedure known as laparoscopy. A fiberoptic endoscope, an instrument originally developed by physicians for viewing the interior of the human knee, is used to determine the bird’s sex and whether or not the bird is sexually mature. Laparoscopy also allows the doctor to evaluate the condition of other internal organs.

After the bird’s sex has been determined, a common procedure for identification is used by placing a tattoo in the wing web of the bird. By convention the right wing is used for males, and left is used for females. Leg banding is another form of identification, however, most available bands can cause serious problems if the bird crushes the band around its leg. The most successfully used band for the larger psittacine birds has been the stainless steel band. (Available from Donna G. Corp, 4903 N. Ardley Drive, Temple City, CA. 91780.) Even with this type of band it is important to choose the right size and fit it correctly.

HOUSING:
Sexed birds must then be placed in housing that will be conductive to breeding. Each species’ individual requirements must be considered when deciding on the type of housing to use. Basically there are two set-ups commonly used: cages and flights.

Flight breeding is the most commonly used method. Flights are built in many sizes, but most commonly they enclose an area that is long and narrow. Flights used for breeding usually are large enough for a person to enter standing up and the sizes depend on the needs of each species. The flight sizes vary greatly. They are all usually from 91 cm (3ft.) to 122cm (4ft.) in width but lengths can vary from 183cm (6ft.) to 9.1 m (30R.). Many of the larger Australian parakeets, (Barnardius, Alisterus, Aprosmictus, Purpuracephalus, and Polytelis) need the longer flights. The width is not as important as the length, as the length is important for flying.

Cage breeding has risen in popularity in the 1980’s. Cages differ from flights in that they are smaller in area and suspended above the ground. They are usually made completely of wire. This allows fecal matter and old food to drop through the cage floor to the ground. Cage construction costs less than flights, and cages can be moved more easily. The main problem with cages is that aviculturists tend to make cages too small for the birds to exercise.

Maintaining birds at their peak condition is necessary. Birds in captivity such as Amazons (Amazona) have a tendency to become overweight. This can be countered through diet control and providing enough room for exercise. Overweight females may have problems with egg-binding, while too-fat males will simply not breed and infertile eggs will be produced.

At this point, the science of reproduction has really just begun. Placing each bird with a compatible mate is one of the key elements in successful breeding. There area couple of ways to accomplish this, depending upon the species. Most psittacine birds are paired by the keeper and placed into a flight or cage. However, compatibility is not guaranteed by this method. I believe that letting each bird choose their mate is the best method because it dramatically increases the chance of getting a compatible pair. This method is called pair bonding. Several birds of both sexes are placed together in a large flight. Within this group the birds will pair off, and each pair may then be placed in a flight or cage for breeding. Good compatibility between the pair is a major step in breeding the many parrot species from the very common to the more difficult-to-breed species.

NESTING:
Placement and size of nest-boxes are important factors in encouraging a pair to nest. Since most psittacine birds prefer privacy, the opening to the nest-box should be faced away from human traffic and the sides of cages should be solid. When different breeding pairs of the same species can see each other, males may become aggressive and fight with their own mates because they are unable to drive off the other males. If flights or cages have been built without solid dividers, it is important to place double wire between them and seclude the nesting area with solid partitions. The double wire keeps the adjacent pairs from chewing toes through the wire. It is also important not to place known aggressive parrots of the same species in adjoining flights. I n almost every species nest-boxes may be placed in the flights or may be placed on the outside of the flights with a hole cut out in the flight wire to allow the birds to enter the nests. In cage breeding, the nest or nests are usually placed on the outside of the cage. Even birds of the same species may choose to nest in different areas in the cage. When setting up nests, it is best to have more than one available to them. They can be placed in several areas. The most common being one under the sheltered area of the aviary, one in the middle and one at the opposite end. Also some parrots have a preference of which direction the nest is facing, so the box may have to be switched to a different wall.

The size of these boxes varies according to the size of the species The shapes can be vertical, horizontal or slanted. Each pair of birds should be offered a choice of two shapes initially. Some of the materials used for nest-boxes include wood, oak barrels, palm longs and metal drums. Wood is a common choice, since psittacine birds are destructive, it is usually best to use thick wooden planks 10cm (4in.) thick. Since this is not always available, wire or metal sheeting is sometimes used to line the inside of the nest-boxes, but birds may work the edges loose and injure themselves. Formica can be another alternative Since the entrance is usually the first place of bird chews, it should be covered with metal sheeting. Parrots prefer to be as high as possible, so I place nest-boxes and perches near the top of the cages to give them a feeling of security. However one group of parrots, the macaws, will apparently nest at any height, including ground level. All deep nest boxes must have a stable ladder placed inside them from the nest material to the entrance or the bird may become trapped and be unable to get out.

A small door should be placed near the bottom of the nest-box. This entrance is used for inspection of eggs and chicks and for adding nesting material. The nest material used by aviculturists varies greatly. The most common materials used are pine and cedar shavings. Fine sawdust should not be used as it may enter the mouth and eyes of the babies. Combinations of material including shavings, peat moss, sterilized potting soil and top soil are commonly used. This is used mainly with the hopes of increasing humidity. All of the above have been used with success, but it is important that one checks for fungal and bacterial growth within the nest. This can be very detrimental to both the parents and young. It must be noted that parrots can regulate the humidity around the eggs with their bodies.

When building artificial nests, it is important to try to simulate the nest conditions found in the wild. Most birds prefer a confined nest with a small entrance hole.

INCUBATION:
The incubation period for most parrots is between 16 and 20 days; usually the larger the bird, the longer the incubation time. Aviculturists are not certain if there is a difference in the humidity requirements of egg of tropical and desert species, or of species found at low and high altitudes. Some incubating parents can adjust the humidity in the nest by soaking their chest feathers in water to dampen the area around the eggs if needed.

It is often necessary to remove eggs from the parents and artificially incubate them. This is done when the parents do not incubate well or break their eggs. Most guidelines for artificial incubation come from the poultry industry and pigeon fancy and the exact temperature and humidity requirements of the psittacine egg are not yet known. Temperatures may vary during the course of incubation and they almost certainly vary from species to species. No long-term studies of the natural incubation requirements have been completed at this time.

In the last few years, aviculturists have moved toward lowering the artificial incubation temperatures for parrot eggs. The usual 37.5°C (99.5°F) dry bulb and 30.0°C (86°F) wet bulb temperatures is now in doubt as being the optimum for all species. Several aviculturists have tried dry bulb temperatures of 36.9°C (98.5°F) to 37.4°C (99.3°F) and are getting good results. The present lack of data on optimum artificial incubation temperatures and humidities is a great detriment to aviculture. With the new technology and equipment available in the field of electronics, we should be making quick progress toward filling these information gaps.

The young of all parrots are altricial upon hatching. That is to say, they are blind, helpless and totally dependent on their parents. Occasionally the parents do not feed their young well and these must be removed for hand-rearing. This is often true of first-time parents who then feed-subsequent clutches well. It is best to allow them this learning experience and remove the babies only if necessary.

Removing babies from the nest often encourages the parents to lay an extra clutch in the same season. Hand-reared young are very calm in temperament when weaned. I feel it best to allow the parents to raise their own young fora short initial period before removing them, as the babies gain weight more quickly in those critical first two to three days when parent-fed. I n the later stage, the babies can be hand-fed equally or better than in the nest. Exact reasons for this are still unknown. The optimum age to remove babies from the nest varies with each species but is usually between ten to twenty-one days of age. If pulled too early the baby may not have that good start from his parents but if pulled too late, may proved more difficult to hand-feed and later, to wean.

The most challenging aspect of hand-raising is that of newly hatched babies, for they are hand-fed from day one. These are babies that have been hatched in the incubator or by the parents that are destructive to their babies for some reason. Hand-rearing day old babies has not always been done with a high percentage of success. For one thing, they miss getting the bacteria from the parent’s crop lining. A high-quality, nutritious formula is a must but also necessary are good handling techniques. Abundant time and patience are required for hand-rearing, but it is a most rewarding and advantageous aspect of aviculture.

DIETARY REQUIREMENTS:
It is impossible to feed most captive parrots the food they would eat in the wild. Those that naturally eat seeds, seeding grasses, wild berries and fruits are the easiest to convert to a captive diet. Specialized feeders, such as lories and lorikeets, must have special attention to their dietary needs, and they take much longer to adapt to captivity. Usually a nectar substitute is given along with a variety of fruits.

Most parrots are given various dry seeds as the primary element of their captive diet, and sunflower is the most commonly supplied. Unfortunately, some birds will eat sunflower to the exclusion of other foods and although it is a perfectly good seed, an exclusive diet of it is nutritionally unbalanced and may lead to overweight parrots. To remedy this, daily attention should be paid to their diet and they can be given a limited supply of high fat content seeds. Or, sunflower can gradually be replaced with safflower which is very similar nutritionally to sunflower but much smaller. A parrot would have to work longer to consume an equal amount. Eliminating sunflower has the advantage of encouraging sampling of a greater variety of foods offered and hopefully result in a better-balanced diet. We have successfully placed almost all species of large parrots on a sun-flower-free diet, including Amazons, African Greys, Eclectus, all species of Cockatoos and the miniature and medium-sized macaws. In addition to seed in the captive diet, a great variety of fruits and vegetables can be offered and in fact this is absolutely necessary with some species (Eclectus Parrot, Fig Parrots, Pesquet’s Parrot). Monkey chow and dry dog food help to supply needed proteins and vitamins. Supplements of vitamins and minerals, especially calcium, should be given. Most seeds contain a large amount of phosphorous, so supplementary calcium is essential to maintaining the physiologically correct calcium/phosphorous ratio. Natural or cultivated foods, free of poisons and pesticides, can be made available to the birds, such as berries, eucalyptus branches with buds and leaves, hawthorns and natural greens, like chickweed and dandelions. Germinated and sprouted seed can be given but care must be taken that fungal growth does not develops and possibly be consumed by the birds.

There are many types of nectar foods for non-seed eating parrots and they are composed mainly of liquified fruits and vegetables, with vitamins and mineral additions. A source of protein should also be mixed in the food of the common nectar feeders. The nectar diet can also be used to feed other species as a supplement (Swift Parakeets, Lathamus discolor; Fig Parrots, genera Opopsitta and Psillaculirostris; Hanging Parrots, genus Loriculus; and the Eclectus Parrot).

Many parrots can subsist on a seed-only diet but if the goal is reproduction, seeds are not enough. Breeding birds should be at peak condition to want to breed at all and to produce healthy offspring. Diet can also help bring parrots into their breeding cycle at the right time of year.

NOTES ON UNUSUAL OR ABNORMAL OBSERVATIONS I N SEVERAL OF THE PARROT GROUPS.

(1) Lories and Lorikeets (Family Loriidae)
This group of parrots is characterized by a special adaptation of the tongue f or nectar feeding. The tip of the tongue has long papillae which extend in use, giving the name, “brush-tongued” parrots. In the wild, they feed on pollen, fruits, buds and small insects, in addition to nectar. Therefore, in captivity, other foods should be offered, along with the prepared nectar.

The San Diego Zoo has been working with a great variety of lories and lorikeets for several years. A source of protein is added to their basic diet of cane sugar, fruits, vegetables, boiled rice, bread and of course, nectar. Human protein/vitamin concentrates, such as Super Hydramin (Nion Corp., Los Angeles, CA) are fed.

There are many species of these birds native to the high altitudes of New Guinea and these consequently adapt well to cold climates in captivity.

(2) Cockatoos (Family Cacatuidae)
As a general rule, the male of many of the cockatoo species can become very aggressive toward his mate during the breeding season, especiallythe Moluccan; Major Mitchell, Cacatua leadbeateri; the Lesser Sulphur-crested species, Cacatua sulphurea; and the Sulphur-crested species, Cacatua galerita. This may occur even in reproducing pairs that have previously raised young successfully. Disaster may result if male is ready to breed and the female is not. He will try to drive her into the nest and if she does not respond favorably, he may injure her seriously by biting heron the base of the upper bill. Be wary of this if you have an older male with a less mature female. If this may be the case, be sure to remove the nest-box from the aviary until she is more mature or provide extra nest-boxes along with shelter in the form of tree limbs high in the aviary so that the female may escape from the male if she needs to.

The Galah, Eolophus roseicapillus, is usually the earliest species to nest in captivity and eucalyptus leaves are a favorite choice of their nest material.

(3) Fig Parrots (Genuses Opopsitta and Psittaculirostris)
Fig parrots have been brought into captivity only during the last few years. The difficulty of establishing them is proven by only one successful breeding on record at the time of this writing. Very little is known about their natural history, i.e., diet or nesting habits in the wild. These parrots (and many of the tropical species of lories and lorikeets) take an unusually long time to become comfortably settled in captivity, probably due to the extreme dietary and climatic changes. However, many of them that have made it through several seasons in captivity then go on to live for many years and this contributes to the author’s opinion on the slow acclimation of these birds and the patience needed to breed them. Nest-boxes should not be set up in the first year of captivity as this may add intolerably to the stress of a new diet and environment.

Instead, the birds should be given minimally one full year to settle down before any breeding is encouraged. Both single pair and colony breeding of fig parrots have been attempted with an equal lack of success. As they are seen in pairs or small groups in the wild, I feel they should be isolated in pairs in the aviary. These birds have a tendency to become egg-bound, perhaps because of cold temperatures, a definite factor in this condition. They prefer to nest in captivity following their natural cycle, which unfortunately means breeding during the winter in the northern hemisphere. A climate-and-humidity-controlled room may be used advantageously with this group.

(4) Pesquet’s Parrot (Genus Psittrachus)
It must be noted that this uncommonly kept parrot does not eat seeds and if they do accept it at all, it is usually hulled and mixed with a soft food. Soft food is a must for these parrots and this can consist of soaked dog or monkey chow, read or sponge cake. It can be soaked in water or in a nectarwith avitamin/mineral powder mixed in. Additionally, as wide a variety as possible of fruits and vegetables should be offered. Yams were the key food in acclimating a group of these birds at the Los Angeles Zoo in the 1970’s. The first successful breeding in the U.S. took place there in 1980. (Personal communication – Mike Cunningham, Curator of Birds, Los Angeles Zoo)

(5) Eclectus Parrot (Genus Eclectus)
The female in this highly dimorphic genus is the more dominant of the pair. Serious attacks generally do not occur, but great care should be taken when placing adults together. It is ideal to allow two young birds to grow up together. If possible, the male should be older than the female and not the reverse. After working with these parrots for many years with a result of over eighty young produced, they still present a challenge to this aviculturist. The main problem in breeding Eclectus is infertile eggs, because the female often becomes so dominant that the male fears to approach her for mating. This can go on for years. Observation of the birds’ disposition toward one another is very significant and we have taken up to nine months with the introduction period. Methods include placing the female and male in adjacent cages or by placing the female in a small cage within a flight occupied by the male. The very best way to achieve optimum compatibility is by observing pair bonding within a large group of birds, still a rare opportunity at best. I have seen some females that have never accepted a mate in either an individual or group situation and these simply may not be useful in a breeding program.

Another note of interest is that the Eclectus parrot will nest during the southern hemisphere breeding season. Almost all pairs, including captive-bred birds, will bred in the wintertime in the northern hemisphere, so precautions against the weather must be taken at that time.

(6) Australian Parakeets (Family Psittacidae)
This group of parrots are among the most commonly bred in captivity but some observations can be of use. Many species, and mostly those found in the northern part of Australia, will breed earlier than the rest and nest-boxes should be placed in their aviaries early. Also, some provisions may be needed in very cold climates to heat the bottom of the boxes to keep the babies from freezing. Several species of note in this group include the Red-rumped Parakeet, Psephotus haematonotus; Many-colored Parakeet, Psephotus varius; Hooded Parakeet, Psephotus chrysopterygius dissimilis; Golden-shouldered Parakeet, Psephotus c, chrysopterygius; and Northern Rosella, Platycercus venustus.

In some of the species (Hooded Parakeet, Golden-shouldered Parakeet) that may nest in termite mounds in the wild, a tunnel can be added to the outside of the nest-box to encourage them to nest. This tunnel of wood need not be over 1 5cm (6in.) in length but it darkens the entrance hole, thus simulating the termite mound.

(7) Kakarikis (Genus Cyanoramphus)
These parakeets originate from New Zealand and it is important to note that they become distressed in heat and prefer cool weather. One should breed them through the cool months and extra shelter should be added in the summer if they are on eggs or young.

(8) Macaws (Genus Ara)
Ever since the endoscope enabled aviculturists to sex macaws, there has been a dramatic rise in the reproductive rate of this group of birds. Most macaws will pair bond easily and then become very compatible. It must be noted that one must know the sex of each bird when several are placed in a large aviary for pair bonding. Macaws are among the few parrots that will form pair bonds between individuals of the same sex. This is not very common, but certainly will not result in offspring.
I personally believe the number of macaws reproduced will increase dramatically in the next few years, not only because of surgical sexing but because of their bonding nature and lack of aggression toward each other. For this reason, I feel there will be many more macaws reproduced than cockatoos.

Macaws aggressively defend their nests when on eggs and/or babies. This defense is aimed at human interference and may result in breakage of eggs or injury of young as the adults do not leave the nest when disturbed. It is best to keep human intrusion to a minimum and to supply a door to block the adults from returning to the nest when checking eggs or young.

(9) Amazons (Genus Amazona)
Amazons and other groups of large South American parrots (Pionus and Pionopsitta pileata) tend to become sedentary in captivity. They may become overweight and their diet must be monitored so that seeds and other fatty foods are kept to a minimum. Cage breeding has proven very successful in reproducing this group of birds. The lack of large Amazons reproduced in captivity may be due to the lack of effort to breed them, for great numbers are imported from the wild and used for the pet trade. Amazons are another group of parrots that may break eggs in their nest, because of their aggressive nature toward humans during the nesting cycle. Often this aggression is transferred to the female when the male becomes highly agitated and one must beware of this.

(10) Conures (Genuses Aratinga, Pyrrhura, Enicognathus)
Consures in general have not been raised in good numbers until recent years and many species were only bred for the first time in the past five or ten years. I feel this is true, not because they are necessarily difficult to breed, but rather because no one has made a serious effort to do so until recently. Hundreds and thousands of conures were imported into the U.S. in years past, making them cheap and easily obtainable, and most went into the pet trade. However, many species are not now being imported and hopefully it is not too late to see them breeding successfully in captivity.

Many species have now been successfully reproduced in single pair breeding situations using the cage breeding method. The young, when hand-raised and kept back for breeding, have bred very well and much sooner than wild-caught birds. The more colorful conures are now being commonly reared, but still many of the less colorful ones are not being avidly worked with by any aviculturists.

SUMMARY:
In the past few years, strides have been made in many areas in reproducing parrot-type birds in captivity. Modern techniques are just now being utilized, especially in avian medicine and in safe, surgical sexing of birds. We are still lacking in depth knowledge in the critical area of artificial incubation requirements. Communication and dissemination of knowledge in the avicultural world must be a constant goal.

We may be very close to the time when many parrot species will not be available for aviculturists to work with. So many genuses and species are already sadly lacking in captive numbers, and there is little hope that this condition will change. Cooperation among aviculturists and individual specialization among the parrot groups will soon be a must.
Success for the future will depend on the dedication of all aviculturists everywhere. They will need patience, hard work, cooperation and most of all, they will need a keen appreciation and knowledge of their birds’ needs.

ADDITIONAL REFERENCES:
Bates, J., and R.L. Busenbard. 1969. Parrot and Related Birds. T.F.H. Publications, Inc., Jersey City, New Jersey City, New Jersey.
Berger, A.J. 1977. Fitness of Offspring from Captive Populations. In Endangered Birds, Management Techniques for Preserving Threatened Species. 315-320 University of Wisconsin Press.
Berry, R.S. 1975. Precarious Perch for a Parrot. Animal Kingdom. Oct./Nov. Pgs: 25-30.
Clements, J.F. 1978. Birds of the World: a Checklist. The Two Continents Publishing Group, Ltd., New York.
Forshaw, Joseph M. 1977. Parrots of the World, T.F.H. Publications, New Jersey,
Harrison, Greg J., D.V.M. Endoscopy as a Means of Pairing Birds. The A.F.A. Watchbird, Vol. VIII, Number 1. Feb./March., 1981. pg. 6-8.
Lendon, A.H. 1973. Cayley’s Australian Parrots in Field and Aviary, Sydney. Angus and Robertson.
Low, Rosemary. 1980. Parrots, Their Care and Breeding. Blandford Press Ltd., Poole, Dorset, United Kingdom.
Low,, Rosemary. 1977. Lories and Lorikeets. T.F.H. Publications, Neptune, New Jersey. Noegel, R. 1979. Amazon Husbandry. The A.F.A. Watchbird.
Pasquier, Roger F. (ed.) 1981. Conservation of New World Parrots. Proceedings of the ICBP Parrot Working Group Meeting. St. Lucia. 1980. Smithsonian Institution Press.
Thompson, Dale R. 1981. Techniques in Psittacine Aviculture, Proceedings of 30th. Western Poultry Disease Conference. University of California, Cooperative extension.