Advertisement

Psittacine Incubation and Pediatrics

      Keywords

      As avian veterinarians, we can help by educating our pet bird owners and avicultural clients. We can support our avicultural clients' efforts. We can make an “Aviculturist” binder displaying aviculturists' cards and listing the bird species they breed and sell. We can support and facilitate direct breeder sales. Direct sales result in healthier pet birds as it is safer, for babies especially, to go directly from breeders to their new home.
      • Romagnano A.
      Aviary design and management.
      Education can save many parrots and is very important in today's avicultural climate. The small aviculturist dominates the industry and needs our help. Aviculturists are a group of hard-working individuals who could benefit greatly from well-planned veterinary consults. Some aviculturists keep abreast of husbandry developments but resist preventative medical checkups and nutritional advances, and may even opt to treat many of their sick and injured birds at home. Preventative avicultural medicine can be a tough sell, as it may appear to be a costly process to examine an entire collection, but in the long run, it is more cost effective than triage medicine. The survival rate is much lower with triage or emergency medicine than in a collection with routine preventative medicine. Although small aviculturists can be seasoned and knowledgeable, as mentioned, they are more commonly isolated, uninformed, and eager to learn. Avian veterinarians can make a difference by focusing on avicultural education and pediatrics. This is important because aviculture is the only future for many parrot species. Further, aviculturists' predominantly have their birds' best interests at heart and most are very receptive to new ideas. This is especially true if we, as avian veterinarians, take the time, on a regular basis, to educate them, answer their questions, and address their concerns.
      Like psittacine pediatric medicine and surgery, a significant part of avicultural medicine is HUSBANDRY, and the most important husbandry issue is nutrition.
      • Romagnano A.
      Aviary design and management.
      Nutrition is important at all levels of psittacine development. Hence, the avian veterinarian must become knowledgeable of neonatal and juvenile handfeeding formulas and techniques, weaning feeds, adult and breeder bird pellets, as well as specific nutritional requirements of parrots of all ages.
      Avian veterinarians must be readily available, in the author's opinion, on a 24-hour-a-day basis. They must also take the time to educate their avicultural and baby bird clients, both individually and in groups. Education can take place within the clinic, on site at breeding facilities, or at bird clubs and national meetings. The important thing is to educate, consult, listen, and help these people and consequently help their birds.
      The first requirement for successful captive breeding is a true pair.
      • Romagnano A.
      • Hadley T.
      Sex differentiation and reproduction.
      Gender determination is paramount for successful psittacine aviculture. Sexing is necessary because psittacines are predominantly monomorphic. This has resulted in many same-sex pairs, thought to be true pairs, inadvertently set up for years.
      • Romagnano A.
      • Hadley T.
      Sex differentiation and reproduction.
      This is especially true when a female pair is producing eggs. Accurate sex determination is also important because sexing is a veterinary service and the avian veterinarian is making a diagnosis. Various options for sexing are available; hence the avian veterinarian can choose the method most suitable to the patient and the client. Additionally, sexing of baby birds can help breeders who wish to sell their birds as a particular gender at an early age.

      Sexing

      Visual Sexing

      A few psittacine species are sexually dimorphic and can be definitively sexed by visual examination. Some examples follow:
      • Eclectus parrot: Males are green and females are vibrant red and purple.
      • White-fronted Amazon parrot: Males have red versus green feathers on the upper wing coverts, the edge of the carpus, and the alula.
      • Pileated parrot: Males have red feathers on head, and females has green.
      • Red-tailed black cockatoos: Females have spots on head, body, and wing feathers, and the tail is barred with yellow-orange feathers. Males lack spots and the tail has red bars.
      • White-tailed black cockatoos: Females have white ear coverts and light horn-colored beak. Males have gray ear coverts and dark gray beaks.
      • Gang-gang cockatoos: Males have red head and crest feathers, and females are totally gray, barred with grayish white.
      • Pesquet's parrot: Males have red feathers behind the eye, which are absent in females.
      • Australian king parrot: The males have scarlet red feathers on the head, neck, and under parts. Females have green feathers on the head and chest and red feathers on the lower abdomen. The beak is red-orange and black tipped in the male and black in the female.

      Vent Sexing

      Vent sexing is an accurate sexing method for one psittacine species, the Vasa parrot, where a penis-like appendage is found in male birds.

      Surgical Sexing

      First performed in the 1970s, surgical sexing is by far the best and most direct method of gender determination in monomorphic psittacine birds of almost any age. The main disadvantage of surgical sexing is the inherent, though minimal, surgical and anesthetic risk. The advantages of surgical sexing are many, including a complete visual assessment of the internal organs on the left side of the bird's body as well as assessing the birds for internal disease.

      Cytogenetic Sexing

      First performed in the 1980s, cytogenetic sexing is a nonsurgical alternative for sexing birds. A freshly plucked contour blood feather is the preferred source of chromosomal DNA in psittacine birds. The plucked feather is immediately placed in media for overnight mailing to a cytogenetic laboratory. Chromosomal analysis is performed on cells cultured from the submitted feather.
      • Valentine M.
      Chromosomal analysis.
      Advantages of cytogenetics include karyotype evaluation and identification of chromosomal defects. Cytogenetic defects identified in psittacines include chromosomal inversions, chromosome translocations, triploidy, and ZZ ZW chimerism. These defects significantly reduce fertility. Disadvantages of feather sexing include a 2-week turnaround time and the possibility of culture failure.
      • Valentine M.
      Chromosomal analysis.

      DNA Sexing

      First commercially available in the 1990s, the newest means of nonsurgical sex determination in avian medicine is DNA sexing. This technique involves acquiring and submitting a small amount of whole blood or a few blood feathers to a laboratory. The DNA is run on an electrophoretic gel (Southern blot), and the resulting bands are probed and compared with male and female controls. The main disadvantages of DNA sexing is the turnaround time, the lack of species-specific probes in some cases, and the possibility of error due to sample mixup or sample contamination with DNA from a bird of the opposite sex.

      Incubation and Hatching

      Successful incubation and hatching require intensive husbandry. Similarly, altricial psittacine chicks require intensive care from day 1. Neonates hatch with eyes closed and little to no down and are unable to thermoregulate, and they need to be hand-fed.
      • Clubb K.
      • Swigert T.
      Commonsense incubation.
      • Clubb S.L.
      • Phillips A.
      Psittacine embryonic mortality.
      • Romagnano A.
      Reproduction and pediatrics.
      • Clubb S.
      Psittacine pediatric husbandry and medicine.
      Thus, in addition to preventative and triage medicine, the avian veterinarian can help the aviculturist by evaluating the following processes: incubation, hatching, handfeeding, neonatal development, and weaning.
      Natural incubation by captive psittacines is affected by many factors, including demonstration of normal breeding behaviors by both parents, health, diet, species, origin (wild caught or hand raised), experience, environment, egg integrity, and nest box design.
      • Romagnano A.
      Reproduction and pediatrics.
      • Martin S.
      • Romagnano A.
      Nest box preferences.
      Perhaps the most important of these is the demonstration of normal breeding behaviors. The female should act broody and prepare for and care for her nest of eggs. The nest should be prepared with the help of her mate and be kept clean and well protected.
      • Romagnano A.
      Reproduction and pediatrics.
      The male should take on the role of provider and feed the female consistently throughout the pre–egg-laying and post–egg-laying periods. One or both of the parents may feed the offspring. Males are known to lose weight during this time as they are passing the nutrition on to their mate and offspring.
      • Romagnano A.
      Reproduction and pediatrics.
      Nest box parameters such as cleanliness, shape, depth, width, height, and degree of openness and the amount of lighting are important for breeding success.
      • Martin S.
      • Romagnano A.
      Nest box preferences.
      Broken or cracked eggs are susceptible to bacterial or fungal infections, and should be repaired with nail polish and incubated artificially.6
      Hatchability of artificially incubated eggs pulled at day 1 is lower than that for eggs naturally incubated for the first 7 to 14 days.
      • Romagnano A.
      Reproduction and pediatrics.
      Further, large psittacine eggs seem to be more tolerant of incubation from day 1 than are the eggs of smaller psittacine species. Incubation of eggs from day 1 is tedious and time consuming but frequently increases overall production from the pair. This increase occurs despite increased individual egg loss because pulling the eggs at day 1 encourages the hen to lay again, thus increasing the number of eggs laid per clutch, as well as the number of clutches laid per year. Birds should not be encouraged to clutch more than 2 or 3 times a year.
      Successful artificial incubation is dependent on several parameters including temperature, humidity, airflow in the incubator or hatcher, vibration, and egg rotation. Egg rotation is very important in artificial incubation. It is required to prevent embryo adhesion to the shell membranes. Parents will turn their eggs every 35 minutes.
      • Romagnano A.
      Reproduction and pediatrics.
      Inadequate turning in artificial incubation results in early-dead-in-shell, malpositioned, or late-dead-in-shell embryos. Good-quality commercial incubators turn eggs at different rates on various types of timed mechanical rollers, with 10 turns per day being the average.
      • Romagnano A.
      Reproduction and pediatrics.
      A minimum of 5 turns per day is required in machines where automatic turning is not an option.
      • Romagnano A.
      Reproduction and pediatrics.
      A popular and reliable artificial incubator is the Grumbach (Grumbach, Assalar, Germany). Artificial incubators and hatchers should be cultured for bacteria and fungi several times a year, as well as a DNA probe tested for polyoma and psittacine beak and feather virus. Units should also be cleaned and gas sterilized yearly at a minimum, whenever empty or ideally between sets of eggs.
      Incubation temperature and humidity vary for different psittacine species but range from 98.9° to 99.3°F (37.3°C) and 30% to 45%, respectively. Digital hygrometers work best to monitor humidity. Incubation room temperature is ideally maintained at 73° to 75°F (22.5°C) with a humidity of 43% to 48%. Most psittacine embryos are best hatched at 99.5°F (37.5°C) with a hygrometer reading of 65% to 75%.
      • Romagnano A.
      Reproduction and pediatrics.
      Artificially incubated eggs are candled to monitor development and should be moved to the bottom of the incubator and no longer turned once draw down has been noted, as this is when internal pipping begins. A simple small flashlight can be used for candling. Some aviculturists will candle daily, but the majority candle weekly or biweekly as psittacine eggs are less tolerant of handling than are poultry eggs. However, candling, a necessary form of handling, is important in determining embryo fertility and viability. The critical periods of development for psittacines are the first few days of incubation and the time from internal pip until hatching.
      • Romagnano A.
      Reproduction and pediatrics.
      During these times, the embryo is most susceptible to adverse handling and/or improper incubation parameters. Incubation times vary for different psittacine species and range from approximately 18 days in budgerigars to approximately 30 days in palm cockatoos.
      The first sign of fertility are blood vessels radiating uniformly from the embryo in a branching pattern around day 4 or 5 in some species, but they can be seen as early as 3 days. Eggs with clear yolks showing no signs of blood vessels or development by day 7 are infertile, or early dead in shell, and should be removed from the incubator (or nest). A healthy developing psittacine egg should lose between 11% and 16% (average 13%) of its water weight by diffusion during incubation (day 1 to external pip). The air cell should form at the larger rounded end of the egg during this period of weight loss. If the humidity is too high, however, the air cell will be small, and if it is too low, then the air cell will be larger. Washing of eggs, typically done in the poultry industry, is thought to be risky for psittacine eggs and is not recommended.
      • Romagnano A.
      Reproduction and pediatrics.
      The normal psittacine embryo assumes the hatching position with its head below the air cell just before hatching. Psittacine embryos have shorter and thicker necks than chicken embryos and do not normally tuck their heads under their right wing.
      • Romagnano A.
      Reproduction and pediatrics.
      Instead, they barely tuck their head and typically lay it close to the right wing tip. Hatching occurs in stages (draw down, internal pip, external pip, emergence from the egg) and is the time of highest mortality in embryonic development. Approximately 24 to 48 hours prior to internal pip, the air cell expands and extends down, or draws down, one side of the egg, occupying 20% to 30 % of its volume. An increase in the level of carbon dioxide (CO2) then occurs because the gaseous exchange needs of the embryo are no longer met by the allantoic circulation. This build-up of CO2 causes the hatching muscle in the neck to twitch. This twitch causes the egg tooth, which is located rostrally on the tip of the maxilla, to penetrate the chorioallantoic membrane (ie, internal pip). At this point, the embryo becomes a chick, as it begins to breathe air within the air cell. As the lungs begin to function, the right-to-left ventricular shunt in the heart closes, and in certain species a peeping sound may be heard from the egg. At this time, turning of the egg should cease, and it is placed on the bottom of the incubator. Twitching of the abdominal muscles, which occurs secondary to breathing, causes the exteriorized yolk sac to be drawn into the chick's abdomen. With subsequent breaths, the level of CO2 within the air cell rises. When CO2 reaches 10%, the pipping muscle again begins to twitch, causing the egg tooth to penetrate the shell; this is called external pip. At this time, the eggs are moved out of the incubator and into the hatcher. The time between entering the air cell and external pipping may range from 3 hours to 3 days, but is typically 24 to 48 hours for most psittacine birds.
      • Romagnano A.
      Reproduction and pediatrics.
      Malposition and inadequate moisture loss are among the most common causes of embryonic mortality prior to hatching. Malpositions commonly occur secondary to hyperthermia or elevated temperatures, which also cause premature pipping. Two of the most common psittacine malpositions are when the head is located at the small end of the egg and when the beak is rotated away from the air cell. Eggs incubated below optimum temperatures develop slower and typically have increased problems with hatching. Excessive humidity fosters the development of “wet chicks.” These chicks drown at pipping, due to remaining albumin, and are often edematous. Eggs exposed to low humidity may dry out, causing adherence of the shell membrane to the chick, preventing normal pipping.
      All dead eggs should undergo necropsy by the avian veterinarian or aviculturist. During the gross necropsy, the embryo's general condition and position are assessed. Abnormal tissues and fluids are cultured and/or sent off for histopathologic examination. The shell is examined for color, texture, shape, and the presence or absence of stress lines. Thickness of the shell is assessed by differences in texture, as well as transparency and the degree of porosity.

      Neonatal Care and Feeding

      Once hatched, or pulled from the nest, neonatal or young chicks should be housed in warm appropriate environments such as forced air incubators like Lyon Technologies Animal Intensive Care Units (Lyon Technologies Inc, Chuls Vista, CA, USA). They should be on scheduled feeding as described later because nutrition is paramount to their survival.
      Nutrition is also key during conception, incubation, and parental feeding of baby chicks. Parents must be fed nutritionally complete diets including large amounts of fresh fruits and vegetables plus breeder pelleted diets. Larger psittacines should also receive large nuts (hazelnuts, brazil nuts, macadamia nuts); medium psittacines should also receive smaller nuts (pine nuts, pistachios, almonds); and small psittacines should receive healthier seed choices such as safflower, rape, and flax seeds. Vitamin and mineral supplements should not be provided, with the exception of natural cuttlebone. Cuttlebone should be available for all breeding birds both large and small. Crush and serve it in the food bowls for larger breeding birds, and have it secured inside the cages with the soft side facing in for smaller breeding birds.
      A healthy chick should have a healthy vigorous feeding response whether its parents or an owner is feeding it. The chick's feeding response is referred to as “pumping.” If chicks do not pump, then their parents or an owner cannot safely feed them. Therefore, it will not matter how balanced and complete a diet you feed the parents or prepare for a chick, if the chick is not able to receive it safely into the crop.
      Psittacine chicks do best on higher-fat diets, such as Kaytee Macaw Exact or Kaytee High Fat Hand Feeding Formula (Kaytee Products Inc, Chilton, WI, USA). Most psittacines do well on these types of diets, unless they are prone to obesity and hepatic lipidosis, like white and pink/salmon-colored cockatoos. The percentage of solids (the powdered formula) mixed should be 27%. Handfeeding formula should be mixed with clean, hot water. The temperature of the final formula mix should be between 105° and 108°F.
      Temperatures lower than 105°F may result in formula aspiration, especially in Eclectus and African grey parrots, as chicks will not pump if the formula is not warm enough. This will result in aspiration and subsequent aspiration pneumonia. Temperatures of 109°F or higher or microwave reheating will result in crop burns. Microwave reheating causes crop burns because formula is a powder-and-liquid mixture. Unblended tiny amounts of powder can harbor heat, forming a closed ball of heat that explodes when it comes in contact with liquid in the crop, or beyond, in the bird's gastrointestinal tract. Crop burns can take up to 3 weeks to fistulate out of the body and, if not treated properly, can be fatal. If crop burns fistulate into the coelomic cavity, usually in the thoracic area, they are acutely fatal. Hence, it is best to never microwave any food at all for birds.
      It is important to make sure handfeeding syringes be scrubbed clean, disinfected, and dried or discarded after every use. Hot soapy water wash, followed by soaking in diluted Roccal-D (Pfizer) and rinsing with a very dilute chlorhexidine mixture, works well. Every chick should have its own syringe for each feeding. Chicks should be fed on schedule or as soon as their crops are almost empty during the day. It is not necessary to feed chicks after midnight and before sunrise as they need to rest. Poor doers and sick or stunted chicks may need supplemental night feedings. Chicks should be weighed every morning before feeding, and their weights should be recorded, monitored, and compared to growth charts for the same species. Chicks must gain weight daily until weaning. A lack of weight gain or actual weight loss often indicates a problem is developing.
      Chicks being handfed from day 1 require a diluted commercial formula for their first 3 days of life. These neonates should be started on a dilute commercial formula, such as Kaytee Macaw Exact, which should be fed until day 4. The macaw formulas are higher in fat and calcium and lower in vitamin D, all of which are important for healthy neonatal chick development. The diluted formula is given every 2 hours of the first and second days, except during the night, when crops are allowed to empty. On day 2, neonates should receive BENE-BAC PLUS Bird and Reptile (PetAg, Hampshire, IL, USA) (0.1 mL) at their first feeding. The third-day feedings are given every 3 hours.
      By day 4, neonates should be started on an undiluted formula mixture. The schedule of formula feedings after day 3 goes from: 5 times a day for the smallest of birds, to 4 times a day, to 3 times, to 2 times, to 1 times, to weaning for birds of conure size and up. Birds are gradually moved down based on their species and individual size. The amounts fed are based on body weight (BW) early on, later by species (see later). Hence, on day 4, Kaytee Regular Exact is fed to all the white and pink/salmon-colored cockatoos. The cockatoos are fed at 10% BW until 3 times a day, when they are switched to 8% to prevent hepatic lipidosis. Birds that require more fat such as the black/gray cockatoos, thick-billed parrots, hyacinth macaws, green-winged macaws, golden conures, and slender-billed cockatoos do best when fed a macaw handfeeding formula with added fat and fiber (see description). The hyacinth macaws are fed such a formula at 12% BW and the green-winged macaws at 11%; all the other birds in this group are fed at 10% BW. The rest of the macaw species, African greys, Caiques, sun conures, Eclectus parrots, and hawk-headed parrots do best on the Kaytee Macaw Exact handfeeding formula. All these birds are fed at 10% BW, except for the Buffon's macaw, which is fed at 12% of BW. Once the birds reach their twice-a-day feeding, they are gradually increased to a once-a-day predetermined maximum for their species. For example, the maximum volume is 5 mL for cockatiels, 25 mL for sun conures, 50 mL for African greys, and 140 mL for hyacinth macaws.
      At 2 feedings a day the juvenile birds should be offered solid foods, such as pellets (Zupreem Fruit Blend [Hill's Pet Nutrition, Inc., Topeka, KS, USA], Kaytee Rainbow Chunky [Keytee Products, Inc], LaFeber [Lafeber Company, Cornell, IL, USA]), fruits and vegetables, and shaved nut pieces or small nuts such as pine nuts. Vitamin and mineral supplements should not be provided. Be careful with larger pieces of fruits and nut treats with big macaws (eg, whole grapes and ¼ orange slices with the rinds on, etc). Such food items can be swallowed whole, causing crop impaction and gastrointestinal blockage.
      Water bowls should be introduced when the birds are at 1 feeding a day. Once birds are drinking and eating on their own, they can be moved into larger cages or flights. Birds can be trained to use a drinking Lixit L-100 (an automated watering device; ATCO Manufacturing Company Inc) before their water bowls are removed as needed. Birds should always be weighed and monitored closely during the weaning process. Birds should never be force weaned. Instead, each should be treated as an individual and weaned at his or her own pace.
      If baby birds are sold before they are weaned, intense avian veterinary help is needed. Unweaned baby birds continue to perpetuate the creation of special clients, and patients, who need extensive time commitments from their avian veterinarians. Such a service could never be achieved through office visit consultation alone. The methodical repetitive education of their new owners is the best way to help these baby birds.

      Pediatric History and Physical Examination

      Psittacine pediatric medicine is complex, the majority of complicating issues are management related, and the number one management issue is nutrition as described earlier. A thorough pediatric history and complete physical examination are a must.

      Pediatric History

      Note the parent's health and breeding history, the condition of chick's clutchmates and other siblings, and any problems the chick has and may have had during incubation and hatching. Bloodwork, other labwork, radiographs, and even a house-call visit may be necessary.
      As part of the history, evaluate the chick's diet. Note the preparation, temperature, delivery, method of handfeeding, and hygiene, as well as the amount and frequency of feeding. Determine if feeders are washing their hands with a disinfectant soap before handling each chick and between groups of chicks.
      Determine whether the bird's crop is empty before each feed, especially the first feed of the day. Assess environment, housing, and substrate for cleanliness, safety, and warmth. Inquire as to the behavior of the chick, its feeding response, and the color, consistency, and volume of its feces, urine, and urates.

      Pediatric Physical Examination

      The physical examination of the chick should entail evaluating weight charts for daily gain, assessing overall appearance, proportions, and behavior. In neonates, this exam should be performed in a warm room with prewarmed hands.
      • Romagnano A.
      Reproduction and pediatrics.
      • Flammer K.
      • Clubb S.
      Neonatology.
      • Clubb S.L.
      • Clubb K.J.
      • Skidmore D.
      • et al.
      Psittacine neonatal care and hand-feeding.
      • Phillips A.
      • Clubb S.L.
      Psittacine neonatal development.
      • Clubb K.J.
      • Skidmore D.
      • Schubot R.M.
      • et al.
      Growth rates of handfed psittacine chicks.
      Knowledge of different species' growth rates, development, and behavioral characteristics are helpful.
      • Clubb K.J.
      • Skidmore D.
      • Schubot R.M.
      • et al.
      Growth rates of handfed psittacine chicks.
      Owners should examine each chick daily checking for potential problems. They should start from the tip of the beak and end at the toes. The beak should be straight and well aligned and monitored for malocclusion at each feeding.
      • Wolf S.
      • Clubb S.L.
      Clinical management of beak malformations in handfed psittacine chicks.
      The beak should also be warm. The mouth and tongue should be clean, dry, and free of mucus or plaque.
      • Romagnano A.
      Examination and preventive medicine protocols in psittacines.
      The crop should be soft, empty between feeds, and never pendulous. The legs should be straight and properly positioned. The feet should be warm and pointing forward. The skin should be light pink. The droppings should be moist and well formed with a small amount of white urates and urine. The chick should sleep between feedings and not beg incessantly.
      Psittacine neonates are altricial.
      • Romagnano A.
      Reproduction and pediatrics.
      • Flammer K.
      • Clubb S.
      Neonatology.
      • Clubb S.L.
      • Clubb K.J.
      • Skidmore D.
      • et al.
      Psittacine neonatal care and hand-feeding.
      • Phillips A.
      • Clubb S.L.
      Psittacine neonatal development.
      • Clubb K.J.
      • Skidmore D.
      • Schubot R.M.
      • et al.
      Growth rates of handfed psittacine chicks.
      Nourishment, warmth, food, and a safe environment must be provided. Neonatal chicks must be kept in an incubator with an air temperature of 93° to 98°F.
      • Romagnano A.
      Reproduction and pediatrics.
      • Flammer K.
      • Clubb S.
      Neonatology.
      • Clubb S.L.
      • Clubb K.J.
      • Skidmore D.
      • et al.
      Psittacine neonatal care and hand-feeding.
      • Phillips A.
      • Clubb S.L.
      Psittacine neonatal development.
      • Clubb K.J.
      • Skidmore D.
      • Schubot R.M.
      • et al.
      Growth rates of handfed psittacine chicks.
      External heat must be provided until the chicks reach 1½ months of age. Smaller containers lined with white paper towels help prevent spraddle leg, keep each chick safe, and allow their droppings to be carefully monitored. After 1½ months chicks can be moved into plastic containers lined with white paper towels kept in warm enclosures with limited drafts, such as fish tanks. Warmth continues to be an issue, and, if the temperature falls, so may the growth rates, digestion, and viability of the chicks. Poor doers and sick or stunted chicks require higher temperatures than do healthy chicks of the same age. Although it is safest to house neonatal psittacines separately, heat is a bigger issue with solely housed chicks. Chicks housed with others are at risk of trauma issues when hungry babies pump on each other before or during scheduled feedings. Heat and humidity are issues for chicks of all ages; make sure that both are being provided. Older chicks can be kept on white towels so as to continue monitoring of their droppings. Wood shavings or crumbled paper substrates are dangerous for chicks of any age or health status, as they could be ingested. Chicks can also fall or burrow into crumbled paper substrates, causing potential suffocation, regurgitation, aspiration, and death.
      In neonates, most abdominal organs can be seen through the skin. Neonates normally have a visible liver, duodenal loop, yolk sac, and ventriculus and occasionally lung. The lungs and heart should be auscultated. Assess body mass by palpation of elbows, toes, and hips, as keel muscle mass is not a reliable indicator of BW in the very young. Crops should be examined visually for size and color and carefully palpated for thickness, tone, burns, punctures, or the presence of foreign bodies. Crops should also be transilluminated to attempt to evaluate and describe their contents. Skin should be evaluated for color, texture, hydration, and the presence of subcutaneous fat. Normally, psittacine chicks should have beige-pink, warm, and supple skin (Fig. 1). Dehydration causes a chick's skin to become dry, hyperemic, and tacky (Fig. 2).
      Figure thumbnail gr1
      Fig. 1Healthy plump well-hydrated macaw chick.
      Figure thumbnail gr2
      Fig. 2Recently hatched blue and gold macaw chick. Note pink/red tacky dehydrated skin. Not plump, soft, light pink to beige and well hydrated.
      In juveniles, feathers should be examined for stress marks, color bars or shade changes, hemorrhage, or deformities of shafts and emerging feathers. The musculoskeletal system should be palpated and assessed for skeletal defects or trauma in chicks of all ages. Until weaning, cockatoo chicks sit back on their hocks and are balanced forward on their large abdomens. Macaws prefer to lie down. Chicks normally have prominent abdomens, due to a food-filled crop, proventriculus, ventriculus, and small intestine. Beaks should be examined for malformations when the bird's mouth is closed.
      • Wolf S.
      • Clubb S.L.
      Clinical management of beak malformations in handfed psittacine chicks.
      Pump pads (the soft fleshy part of the baby bird's beak at its commissures) should be examined for wounds and the feeding response elicited. Generally, a healthy baby bird should elicit a vigorous feeding response when stimulated at the beak's lateral commissures. The eyes and the periocular region should be examined for any abnormalities including lid defects, swelling, discharge, crusting, or blepharospasm. Normally a clear discharge is noted in the eyes when they are first opening, which typically occurs unilaterally. Eyes begin to open on days 14 to 28 for macaws, 10 to 21 for cockatoos, and 14 to 21 for Amazons. Nares and ears should be examined for discharge and aperture size or absence. The oral cavity should be examined for plaques, inflammation, or injuries.
      If a baby bird dies, gross necropsies can be very informative and should be performed in all cases. Histopathology may lead to a definitive diagnosis facilitating proper preventative medical management of the original collection. With the pet owner's consent and permission, information gained can be relayed to the aviculturist. Based on this information, and the collection's general health history, you can better treat, and hence protect, the rest of the flock.

      Pediatric Diagnostics

      Clinical pathology

      Hematology and clinical chemistries should be performed by taking blood from the right jugular vein. As with adults, blood samples drawn should be less than 1% of the bird's BW. Toenail clips should be reserved for blood sexing only. Young chicks have lower packed cell volumes and lower total protein compared to adults. Their albumin and uric acid values are lower, and their alkaline phosphatase and creatine phosphokinase values are higher.

      Microbiology

      Cloacal culture, crop culture, fecal cytology, and Gram stain examinations should be performed during routine examination. Normally, cloacal and crop flora are gram positive and consist of Lactobacillus, Corynebacteria, Staphlylococcus, and nonhemolytic Streptococcus. Most gram-negative and anaerobic bacteria are considered pathogenic, as are yeast. Choanal cultures should be taken if upper respiratory tract disease is suspected or if choanal papillae are abnormally blunted.

      Radiology

      The crop, proventriculus, and ventriculus are normally enlarged in neonatal and juvenile birds pre-weaning, and the latter 2 take up much of the abdominal cavity on radiographs. Furthermore, muscle mass is reduced.

      Endoscopy

      Endoscopy, and surgery in general, is best performed on the fasted pediatric patient, since the proventriculus, ventriculus, and intestines are normally enlarged in unweaned birds. If the birds are kept warm and stable, anesthesia and endoscopy are quick. It is safest to scope after weaning, but the author has safely scoped much younger birds, birds being fed 3 times a day and less being the cutoff for endoscopy. If feeding occurs soon after recovery, then hypothermia, hypoglycemia, and hypocalcemia are easily avoidable. Endoscopy is useful for foreign body retrieval, syrinx examination, surgical sexing, and exploratory coelomic examination.

      Treatment

      Antimicrobials

      Antibiotic treatment should be based on culture and sensitivity for 7 days. The author believes strongly that all pediatric patients on antibiotics should automatically be put on the antifungal nystatin. Lactobacillus supplementation is also highly recommended after antimicrobial treatment, at hatch, and 2 days after hatch. Mild yeast infections can be treated with nystatin alone for 14 days. Retractable yeast infections should be treated with the systemic antifungal ketoconazole (30 mg/kg) in combination with nystatin for a minimum of 21 days. Refractory yeast infections should also be treated with an acetic acid crop gavage (10 mL/kg) at the end of the antifungal treatment, followed by Lactobacillus.

      Fluids

      In pediatrics, patient stabilization centers around temperature and rehydration. Oral, subcutaneous, and intravascular fluids are all warmed and given as needed. Subcutaneous fluids are the most frequently used (100 mL/kg). In the severely dehydrated neonate, a jugular catheter is the preferred rehydration route.

      Common Pediatric Problems

      Unretracted Yolk Sac

      The yolk sac, a diverticulum of the small intestine, is normally internalized into the abdomen before hatching. It is absorbed over the next few days, providing the chick with nourishment and maternal antibodies. Retention of the yolk sac within the abdomen, another problem, commonly occurs secondary to Escherichia coli omphalitis. Unretracted yolk sacs can also occur secondary to infections but are typically a result of incubation problems, such as elevated incubation temperatures. Chicks with unretracted yolk sacs, and therefore an open umbilicus, should be placed on clean towels in the hatcher or the incubator, and their umbilicus swabbed with chlorhexidine scrub. Crop and cloacal cultures should be taken, as well as yolk sac cultures if the sac is leaking. The chicks should be placed on appropriate antibiotics and oral antifungals. Chicks should also be treated with fluids. If the yolk sac fails to become internalized, surgery is necessary.

      Stunting

      Stunting, commonly caused by malnutrition, is most pronounced in the first 30 days of life. Affected birds have poor growth rates, low weight, and an enlarged head relative to their body size. They also have thin legs and wings and abnormal feather growth including delayed emergence (on the body), misdirection (top of head), and feather stress or color bar lines. Stunted birds are typically poor doers, have crop stasis, and have red, wrinkled, and dehydrated skin. Possible causes of stunting include inadequate warmth, poor nutrition, poor formula preparation, poor and infrequent delivery of formula, and exposure to bacteria and/or fungus. Treatment is supportive and includes placing the chick in an incubator, frequent feeding of high fat formula such as Kaytee Macaw Exact, a crop bra, fluids, and antibiotics and antifungals as indicated by diagnostics.

      Leg and Toe Deformities

      Splay leg, a common deformity, is thought to occur secondary to malnutrition, obesity, improper substrate or enclosures, or a congenital defect. Once identified it should be treated immediately. Usually one leg is affected, but both can be. Juveniles that splay on pellets, or other slippery substrates, may straighten up on towels or packed towels. For best results, affected neonates should be packed in paper towels and/or hobbled. Simple hobbling may be sufficient. For severe cases, hobbling of both feet to a flat small plank, similar to a snowboard, so that the legs are properly positioned and the toes face forward may be necessary. Once both feet are hobbled and attached to the plank, the chick should be placed into a small straight-sided container (Fig. 3). For best results, hobbling of either kind must be changed frequently due to soiling and growth of the chick. If hobbling does not work, ostectomy may be indicated. Crooked, crossed, or forwardly directed toes can be corrected by splinting if caught early; otherwise, surgery may also be indicated.
      Figure thumbnail gr3
      Fig. 3(A) Board-hobbled umbrella cockatoo baby. (B) Board-hobbled African grey baby.

      Constricted Toes

      Constricted toe syndrome, of unknown etiology, occurs most commonly in Eclectus, macaws, and gray parrots. The lesion consists of an annular ring constriction usually on the last phalanx and most frequently affecting the outer toes, numbers 1 and 4. Under isoflurane anesthesia and magnification, rule out cloth or other fibers as a cause. Next, debride the circumferential fibrotic annular band with fine forceps. Finally, put 2 full-thickness longitudinal incisions, medially and laterally, through the constriction band, express accumulated serum, bandage, and monitor for swelling. Soak in warm dilute chlorhexadine solution and massage daily, then re-bandage. Chicks should be cloacal and crop cultured and put on parenteral antibiotics and oral antifungals.

      Beak Malformations

      The 3 most common beak malformations are lateral deviations of the maxilla (scissor beak) (Fig. 4), mandibular compression deformities of the mandible, and prognathism (pug beak) (Fig. 5). Lateral deviation is thought to be congenital or induced by poor handfeeding technique. Mandibular compression is thought to be induced by rough handfeeding technique. Prognathism (pug beak) is thought to be congenital. The first 2 malformations are most common in macaws, while the third is most common in cockatoos. When the chicks are young and the beaks are most pliable, physical therapy and trimming are indicated. After calcification, frequent trimming, acrylic implants, or extensions are often needed to correct the malformations.
      Figure thumbnail gr4
      Fig. 4(A) Scissor beak in a Canindae juvenile macaw, dorsal view. (B) Scissor beak in a Canindae juvenile macaw, ventral view.
      Figure thumbnail gr5
      Fig. 5(A) Prognathic beak in umbrella cockatoo baby. (B) Prognathic beak in umbrella cockatoo baby.

      Regurgitation

      During weaning, the crop normally shrinks in size. Hence, regurgitation of small amounts of food post-feeding signals the need to reduce the frequency of feedings and begin introducing solid foods such as pellets, fruits, and vegetables. Typically, as a bird grows, feeding volumes are increased and the frequency of feeds is decreased. Younger birds will regurgitate if overfed and this can lead to aspiration pneumonia. Repeated regurgitation in a chick that is too young to wean or regurgitation of large volumes may indicate disease or mechanical blockage. Rule out foreign bodies, crop or lower gastrointestinal fungal or bacterial infection, gout, or proventricular dilatation disease. Drugs such as trimethoprim-sulfa, doxycycline, and nystatin can cause regurgitation, especially in macaw chicks. Chicks should be worked-up and started on antibiotics and antifungals as needed. Note that in cases of regurgitation, antibiotics should be given parentally.

      Esophagitis or Pharyngitis

      Infections of the esophagus and/or pharynx clinically manifest as ulcers and white, gray, or yellow plaques in the mouth. Thick oral mucus is common in these cases, and food and debris may accumulate inside and around the mouth, beak, and tongue. Common causes include gram-negative bacterial and yeast infections from unclean formula or water and its delivery. Antibiotics and antifungals should be given orally. Fluids can be given subcutaneously.

      Esophageal or Pharyngeal Punctures

      Esophageal or pharyngeal punctures occur secondary to syringe or tube feeding. They are most common in vigorously pumping birds, like macaws. Esophageal punctures usually occur midway between the pharynx and the thoracic inlet in the cranialmost aspect of the crop. Pharyngeal punctures usually occur in the caudal aspect of the pharynx slightly caudal to the right of the glottis. Emergency surgery is needed to remove subcutaneously deposited food, create a drain, and begin flushing of the wound. The bird must be tube fed directly into the crop so food does not come in contact with the wound during healing. The crop, cloaca, and choana should be cultured, a complete blood count and chemistry submitted, and the bird started on antibiotics and antifungals.

      Crop Stasis

      Crop stasis is very common in neonatal and juvenile birds. Primary causes of crop stasis include infection, crop foreign bodies, atony, burns, dehydration of food in the crop, hypothermia, formula that is too cold or too hot, and inappropriate environmental temperature. Some of the most common foreign bodies include feeding tubes, syringe tips, or bedding material such as shavings. The most common primary cause of crop stasis is yeast or candidiasis. Secondary causes include distal gut stasis due to ileus, intestinal intussusception, bacterial or fungal infection, sepsis, dilation, proventricular dilatation disease, polyomavirus, gastrointestinal foreign bodies, and renal or hepatic failure. Medical and mechanical management are typically needed for the treatment of crop stasis. Treatment includes placing the chick in a warm incubator with oxygen as needed. Crop washing with warm saline and chlorhexidine, after cultures are performed, is done to empty the pendulous crop. Small, frequent gavage feedings along with appropriate antibiotic and antifungal treatment are appropriate. Finally, the chick should be fitted with a crop bra, which is only released during feedings. Diagnostics as described earlier are very important, especially culture, crop and fecal cytology, and bloodwork. Further diagnostics, such as radiography, crop biopsy, and/or reduction, should be performed as needed. Fluids are key in the treatment of both crop and other gastrointestinal tract stasis cases. Oral fluids rehydrate inspissated crop material and hasten its passage. Subcutaneous fluids are the treatment of choice for systemic rehydration (100 mL/kg). Intravenus fluids are best in a severely dehydrated moribund patient. In these cases, placement of a right jugular intravenous catheter is preferred; these catheters are safely maintained for days. If the crop is severely impacted, repeated flushing with warm saline may be needed to empty it. The crop bra mentioned is a simple form of mechanical management for the overstretched crop. The bras are made in-house of VetWrap (3M Animal Care Products, St Paul, MN, USA; a large cross of VetWrap is fit with a horizontal rectangular piece of VetWrap placed where the strips crosses over (Fig. 6). In a severely overstretched crop, reduction surgery may be necessary to facilitate emptying. Further, hypoproteinemia may occur secondary to severe chronic crop stasis. In these cases, whole blood transfusions and metoclopromide or cisapride may be indicated, as long as gastrointestinal obstruction has been ruled out.
      Figure thumbnail gr6
      Fig. 6(A) Slightly thin and dehydrated macaw chick with crop bra. (B) Crop bra preparation strip. (C) Crop bra cross strips.
      Chronic nonresponsive crop stasis may involve mural candidiasis. These cases are best diagnosed with biopsy and require long-term systemic antifungal and antibiotic treatment and acetic acid gavage. Acetic acid acidifies the crop's contents and discourages yeast and bacterial growth. The most common clinical signs of crop stasis are a visibly oversized static crop and regurgitation. Although a manageable problem, crop stasis can be a fatal condition due to dehydration and sepsis and, therefore, demands immediate intervention. Crop stasis, the most common pediatric problem, causes dehydration. Sepsis typically follows dehydration, and together these conditions are the most common killers in avian pediatrics.

      Crop Burns

      Crop burns of the mucosa and skin occur secondary to feeding excessively hot food (≥109°F). The burn must fistulate through and out of the body before surgery and this may take weeks. Clinical signs of crop burn before fistulation include a poor appetite, swelling and discoloration of the neck or crop, and weight loss. If the crop fistulates, a visible scab forms over the burned area, which when ruptured allows food to pour out of the body. If the crop fistulates into the body or coelomic cavity or between the skin and the crop, the event is most often fatal. Step 1 to a fistulated crop repair is aggressive surgical removal of the burned tissue and scab. Next, the skin and the crop tissues need to be delicately separated and closed in separate layers. An inverting pattern may be used on the crop itself. Antibiotics and antifungals are necessary, both before and after surgery. A common mistake is to attempt a surgical repair too early. Trying to remove and close the burned tissue before all the damaged tissue has become evident may result in incorporating damaged tissue into the repair. This will dehisce as further necrosis occurs and requires another surgery.

      Foreign Body Ingestion or Impaction

      Neonates and juveniles are curious and will ingest foreign bodies, if available. If large and within the crop, foreign bodies can be removed via retrograde palpation and a finger swipe or carefully with long hemostats. Alligator hemostats can be especially useful. A ingluvotomy may be required to remove any material that cannot be removed via the esophagus. Smaller pieces, such as wood shavings, may pass through the crop and result in lower gastrointestinal impactions. Emergency surgery is often indicated.

      Less Common Pediatric Problems

      Rectal Prolapse

      Secondary to hypermotility or infection, rectal prolapse has been reported in macaws. If the prolapse is fresh, the tissue may be salvaged. Emergency surgery is indicated.

      Intestinal Intussusception

      Intestinal intussusceptions have been noted by the author in juvenile Amazons, but could occur in any species. Bloodwork and cultures should be taken. Birds should be started on antibiotics and antifungals. Emergency surgery is often indicated; however, the prognosis is grave.

      Hepatic Hematomas

      These are suspected to be secondary to rough handling/trauma or possibly dietary deficiencies. Most reports have been in macaws where the etiology is unknown. Bloodwork and cultures should be taken; chicks should be started on vitamin K1 and given transfusions as needed.

      Hepatic Lipidosis

      Hepatic lipidosis occurs secondary to overfeeding calories or genetic predisposition primarily in handfed umbrella cockatoos, Moluccan cockatoos, and blue-and-gold macaws, but it can occur in other birds.
      Affected chicks have severely enlarged livers visible through the skin and enlarged abdomens and may be pale and dyspnic. These birds need to have their intake per-feeding reduced and their frequency of feedings increased immediately to help decrease their dyspnea. Their dietary fat content needs to be reduced. Bloodwork and cultures should be taken, and the birds should be started on milk thistle and lactulose.

      Gout

      Gout, a clinical sign, occurs secondary to severe renal disease and severe dehydration. In juvenile macaws, gout is thought to occur secondary to excess vitamin D3 and calcium in the diet. In blue and gold macaws, red fronted macaws, cockatiels, and palm cockatoos, a genetic predisposition is suspected.

      Wine-Colored Urine

      Wine-colored urine may occur in juvenile African grey, Amazon, and pionus parrots. It may occur secondary to certain handfeeding formulas and is most obvious on white or light-colored towels.

      Diseases in the Nursery

      Polyomavirus

      Polyomavirus is the most common viral disease encountered in psittacine nurseries. It is highly contagious, has an estimated incubation period of 2 weeks, and is typically widespread before detection. Most affected birds die within 24 to 48 hours. Hence, it is an acute and rapidly fatal disease of hand-raised neonates. Two- to 14-week-old macaws, conures, Eclectus, and ring-necks are most commonly affected. If clinical signs appear at all, they consist of weakness, pallor, subcutaneous hemorrhage, anorexia, dehydration, crop stasis, regurgitation, vomiting, and depression. Hemorrhage is noted at injection sites, plucked feathers bleed excessively, and petechial and ecchymotic hemorrhages appear on the skin. Survivors exhibit poor weight gain, polyuria, gut stasis, and abnormal feathering similar to that seen with psittacine beak and feather disease (PBFD). Asymptomatic infection keeps this virus in the psittacine population. A DNA polyoma cloacal swab test is available to identify actively shedding birds. Thus, the best method to manage polyoma virus is by vaccination with the killed polyoma vaccine manufactured by Biomune (Psittimune APV; Bioimune Co, Lenexa, KS, USA). The entire aviary and all the chicks in the nursery should be vaccinated. Strict nursery husbandry and a closed nursery policy (including showering in) should also be practiced. Biosecurity is the best prevention.

      Proventricular Dilatation Disease

      This is also an important viral disease of the pediatric patient. Affected birds range from 10 weeks and up and the disease may be fatal. In the nursery, chicks may exhibit regurgitation, crop stasis, voluminous feces, weight loss, weakness, and neurologic signs, including head tremors. Biopsy of the ventriculus, the proventriculus, or the crop may be diagnostic, when lymphocytic plasmocytic infiltrates of myenteric plexi are noted. A closed nursery and strict biosecurity are the best tools available to control this virus.

      Psittacine Beak and Feather Disease

      PBFD can occur in neonates, is highly contagious, and is easily spread by feather dust and dander. This viral disease is characterized by pterylodysplasia (abnormal feather growth) and is most often noted in fully feathered chicks. Feathers can be clubbed and can have circumferential constrictions, and sheaths and blood feathers may be retained. A DNA PBFD whole blood test is available to identify positive birds. Positive birds should be isolated and retested in 90 days as some may clear the virus. The disease course may be acute or chronic depending on the age and immunocompetence of the individual. The entire aviary should be tested for PBFD, and positive adult birds should be immediately removed from the collection. Strict nursery husbandry and quarantine should be practiced, and all chicks should be tested before leaving the nursery.

      Poxvirus

      This virus can be problematic in neotropical collections where chicks remain in the nest for any length of time or where juveniles are housed outdoors.

      Microbial Infections

      Microbial alimentary infections are among the most common problems in psittacine chicks. They are typically diagnosed by cloacal and crop cultures and gram stains. Gram-negative bacteria or yeast infections are abnormal in psittacine chicks. Some strains of E coli, Klebsiella spp, and Enterobacter spp are thought to vary in pathogenicity and can be isolated from completely normal chicks. Birds should be treated only if they exhibit clinical signs or if gram-negative bacteria or yeast are identified in large numbers. Further, they should only be treated based on culture and sensitivity. As mentioned earlier, all pediatric patients put on antibiotics must be put on the antifungal nystatin. In cases of regurgitation or stasis, antibiotics should be given subcutaneously until crop emptying or stasis improves. Microbial diseases of importance in the nursery include E coli spp, Klebsiella spp, Enterobacter spp, Pseudomonas spp, Salmonella spp, and Candida spp.

      Chlamydophilia

      Chlamydophilia should be screened for in all cases of nursery mortality, especially if the collection contains budgerigars or cockatiels. Unfortunately, the diagnosis of Chlamydophilia is difficult, and culture and isolation comprise the only definitive test. Chlamydophilia-positive birds must be treated with doxycycline for 45 days. The zoonotic potential of this disease must be discussed with the owners and reported to the health department if indicated.

      Acknowledgments

      The author would like to thank Dr Paul McCurdy and Lisa Smith, CVT for their expert advice and opinion on this article.

      References

        • Romagnano A.
        Aviary design and management.
        in: Ballard B. Cheek R. Exotic animal medicine for the veterinary technician. 2nd edition. Wiley-Blackwell, Ames (IA)2010: 55-60
        • Romagnano A.
        • Hadley T.
        Sex differentiation and reproduction.
        in: Ballard B. Cheek R. Exotic animal medicine for the veterinary technician. 2nd edition. Wiley-Blackwell, Ames (IA)2010: 61-65
        • Valentine M.
        Chromosomal analysis.
        in: Abramson J. Speer B. Thomsen J. The large macaws: their care, breeding and conservation. Raintree Publications, Fort Bragg (NC)1995: 73-77
        • Clubb K.
        • Swigert T.
        Commonsense incubation.
        in: Schubot R.M. Clubb S.L. Clubb K.J. Psittacine aviculture: perspectives, techniques, and research. Avicultural Breeding and Research Center, Loxahatchee (FL)1992: 9.1-15.1
        • Clubb S.L.
        • Phillips A.
        Psittacine embryonic mortality.
        in: Schubot R.M. Clubb S.L. Clubb K.J. Psittacine aviculture: perspectives, techniques, and research. Avicultural Breeding and Research Center, Loxahatchee (FL)1992: 1-9
        • Romagnano A.
        Reproduction and pediatrics.
        in: BSAVA manual of psittacine birds. 2nd edition. Harcourt-Brown, New York2005
        • Clubb S.
        Psittacine pediatric husbandry and medicine.
        in: Altman R.B. Clubb S.L. Dorrestein G.M. Avian medicine and surgery. WB Saunders, Philadelphia1997: 73-95
        • Martin S.
        • Romagnano A.
        Nest box preferences.
        in: Leusher A. Parrot behavior. Blackwell Publishing, Ames (IA)2006: 79-82
        • Flammer K.
        • Clubb S.
        Neonatology.
        in: Ritchie B.W. Harrison G.J. Harrison L.R. Avian medicine: principles and application. Wingers, Lake Worth (FL)1994: 805-838
        • Clubb S.L.
        • Clubb K.J.
        • Skidmore D.
        • et al.
        Psittacine neonatal care and hand-feeding.
        in: Schubot R.M. Clubb S.L. Clubb K.J. Psittacine aviculture: perspectives, techniques, and research. Avicultural Breeding and Research Center, Loxahatchee (FL)1992: 11.1-12.1
        • Phillips A.
        • Clubb S.L.
        Psittacine neonatal development.
        in: Schubot R.M. Clubb S.L. Clubb K.J. Psittacine aviculture: perspectives, techniques, and research. Avicultural Breeding and Research Center, Loxahatchee (FL)1992: 12.1-26.1
        • Clubb K.J.
        • Skidmore D.
        • Schubot R.M.
        • et al.
        Growth rates of handfed psittacine chicks.
        in: Schubot R.M. Clubb S.L. Clubb K.J. Psittacine aviculture: perspectives, techniques, and research. Avicultural Breeding and Research Center, Loxahatchee (FL)1992: 14.1-19.1
        • Wolf S.
        • Clubb S.L.
        Clinical management of beak malformations in handfed psittacine chicks.
        in: Schubot R.M. Clubb S.L. Clubb K.J. Psittacine aviculture: perspectives, techniques, and research. Avicultural Breeding and Research Center, Loxahatchee (FL)1992 (p. 17.1-12.1)
        • Romagnano A.
        Examination and preventive medicine protocols in psittacines.
        in: Orcutt C. Avian medicine. The Clinics Collection, Veterinary Clinics of North America, Exotic Animal Practice, Avian Pet Medicine, Saunders2005: 35-50