Cockatiels Research Articles

Development of thermoregulation and posthatching growth in the altricial cockatiel Nymphicus hollandicus.

The development of thermoregulation and growth during the nestling period of cockatiel Nymphicus hollandicus were examined in this study. It was hypothesised that, in comparison to other altricial species of similar body mass, cockatiel chicks develop endothermy earlier and consequently have less energy available for growth, resulting in reduced growth rates. While poorly insulated and blind at hatching, cockatiel developed endothermic responses in their first week, and were individually effectively homeothermic (with 75% of adult ability to maintain body temperature during exposure to 20 degrees-25 degrees C), by maintaining high metabolic rates (at all ambient temperatures tested) above the predicted resting rates of an adult of similar body mass before parental brooding ceased (12-13 d). Mass-independent metabolic rates were equivalent to those of fledglings at only 20% of the nestling period (37 d), well before adequate insulation was obtained. The Gompertz growth constants of cockatiel were significantly lower than those of other altricial land birds, which supports the hypothesis of this study.

Excretion and metabolic fate of radiolabeled estradiol and testosterone in the cockatiel (Nymphicus hollandicus)

The metabolism and time courses for clearance of radiolabeled estradiol and testosterone were studied in the female cockatiel (Nymphicus hollandicus) using a simple technique of solubilizing dried fecal/urine matter in an aqueous solution. Carbon 14 radiolabeled estradiol and testosterone were injected intramuscularly and the urine and fecal matter collected for the pursuant 168 hr. The predominant radiolabel peak was found associated with the aqueous residue of the ether extracted aliquot for both hormones. High-performance liquid chromatographic (HPLC) separation of solubilized fecal/urine material collected during the first sampling interval (0–4 hr after injection) demonstrated that the majority of the excreted radiolabel was in the form of conjugated steroid metabolites in both the estradiol and testosterone injected birds. Subsequent hydrolysis of the aqueous residue of the ether extracted aliquots and HPLC characterized the estrogen and testosterone metabolites as being estrone/estradiol and a variety of androgen based moieties, respectively. By 24 hr postinjection, 79.4 and 79.1% of the original radiolabel was recovered in birds injected with estradiol and testosterone, respectively. These findings demonstrate that steroid hormone excretion in the cockatiel is a rapid and efficient process that is 79% complete by 24 hr and that the primary excretion products are conjugated metabolites. This study also supports the concept that fecal/urine collection is a practical and efficient method of monitoring sex steroid excretion and provides additional evidence that simple solubilization of fecal matter is a sufficient and efficient method for processing feces for subsequent metabolite measurements. Zoo Biol 16:505–518, 1997. © 1997 Wiley-Liss, Inc.

The potential use of plasma glutamate dehydrogenase activity for the evaluation of hepatic disease in the cockatiel (Nymphicus hollandicus).

A reference interval for plasma glutamate dehydrogenase (GD) (E.C. 1.4.1.3) activity, of 0-8 IU/L, was established for the cockatiel (Nymphicus hollandicus). An automated modification of a commercial manual assay was used. This enzyme is considered liver specific in humans and numerous domestic animals, due to its organ distribution. A similar distribution was found in cockatiels in this study. Maximal enzyme activity was recovered from liver and kidney homogenate supernatants. Minimal activity was detected in skeletal muscle preparations. These results suggest a potential use for plasma GD activity in the evaluation of hepatocelluar injury/necrosis in cockatiels.

Comparison of Procedures to Detect Chlamydia psittaci Antibodies in Cockatiels (Nymphicus hollandicus)

Diagnostic serologic procedures for psittacine chlamydiosis were evaluated using experimentally inoculated cockatiels (Nymphicus hollandicus). Chlamydia psittaci was recovered from subjects on day 16 postinoculation. Seroconversion was confirmed by the direct complement fixation (DCF) test. The blocking enzyme-linked immunosorbent assay was demonstrated to be the most sensitive of three serodiagnostic procedures evaluated from inoculation until day 24 postinfection, with 92% sensitivity and 73% specificity. The DCF test was progressively more sensitive over the duration of the experiment, attaining 100% sensitivity and specificity on the day 24 postinfection. This study confirms the ability of the DCF procedure to adequately detect C. psittaci antibodies. Limitations relating to reproducibility of serologic results under clinical conditions found in this study indicate that a further refinement of tests is required to consistently detect and quantify antibodies.

Egg Production of Cockatiels (Nymphicus hollandicus) Is Influenced by Number of Eggs in Nest after Incubation Begins

Cockatiel eggs hatch asynchronously because most eggs are laid after continuous incubation begins. We manipulated numbers of eggs in the nest after cockatiels began incubating to determine whether number of eggs in the nest influenced clutch size. We also measured plasma prolactin 2, 7, 12, and 17 days after egg laying began to determine whether clutch size covaried with prolactin concentration. We found that total egg production was stimulated in pairs for which the rate of egg accrual was reduced by egg removal, while total egg production was inhibited in pairs for which the egg accrual rate was increased by egg addition. Female, but not male, plasma prolactin concentrations correlated negatively with egg production on day of lay 17 but not before. We conclude that egg production in incubating cockatiels is influenced by feedback from the number of eggs in the nest and that clutch termination may be signaled by rising prolactin levels in females.

Nest box selection by floor laying and reproductively naive captive cockatiels ( Nymphicus hollandicus)

These experiments examined the effects of offering captive cockatiels a choice of two types of nest boxes which differed primarily in type of nest entrance. The nest entrance to cavity-type boxes was circular and relatively small (6.4 cm diameter), while that to shelf-type boxes was rectangular and relatively large (15.2 cm × 26 cm). Cockatiels with histories of laying in cavity-type boxes tended to choose cavity-type boxes for their first and subsequent clutches. Cockatiels with histories of either laying on cage floors or not laying in the previous breeding trial were more likely to choose shelf-type boxes for first clutches but then switched to cavity-type boxes for subsequent clutches. Approximately one-third of reproductively naive cockatiels also chose shelf-type boxes for first clutches but increasingly used cavity-type boxes for subsequent clutches. Cockatiels laid in cavity-type boxes never switched to shelf-type boxes. Fertility, hatchability and fledging success (survival to 3 weeks of age) were all greater in cavity-type boxes, resulting in greater chick production. These results indicate that chronic floor laying can be corrected by offering cockatiels shelf-type boxes and that shelf-type boxes may be useful for improving captive reproductive performance of non-layers and naive layers as well.

TECHNETIUM‐99M AND IODINE‐131 THYROID SCINTIGRAPHY IN NORMAL AND RADIOTHYROIDECTOMIZED COCKATIELS (NYMPHICUS HOLLANDICUS)

Thyroid scintigraphy using sodium 99mTechnetium pertechnetate (99TcO4‐) was performed in normal and radiothyroidectomized cockatiels (Nymphicus hollandicus). 131I scintigraphy was performed in the course of ablating the thyroid glands. The thyroid glands in normal birds were clearly visualized, but were not individually resolvable. Thyroid glands were not visualized in thyroid‐ablated birds. With 99mTcO4 scans, thyroid (or other region of interest)/body count density ratios were used for comparisons of normal and thyroid‐ablated birds. Normal 99mTcO4‐ thyroid/body ratios (mean +/− SD) for the dorsal and lateral views were 1.83 +/− 0.31 and 1.70 +/− 0.34 respectively. Pertechnetate thyroid/body count density ratios decreased (to 0.93 ‐/−0.14 and 0.88 +/− 0.12 for dorsal and lateral views respectively) after thyroid ablation, while crop/body ratios increased. 99mTcO4‐ thyroid scintigraphy, therefore, was capable of detecting hypofunctional thyroid abnormalities in 131I radiothyroidectomized cockatiels.

Development of an experimental model of hypothyroidism in cockatiels (Nymphicus hollandicus)

Summary Hypothyroidism is 2 possible predisposing factor in a number of disorders of companion psittacine birds. We developed and validated a thyroid-stimulating hormone (tsh) response testing protocol for cockatiels (Nymphicus hollandicus), using 0.1 IU of tsh/bird given IM, with blood sample collection at 0 and 6 hours after tsh, and a commercial radioimmunoassay for thyroxine (T4). This protocol was used to document a seasonal sex difference in stimulated T4 values— females responded with higher T4 values than those in males in summer—and a stress-induced depression of baseline T4 values was detected in a group of cockatiels with normal tsh response. An experimental model for mature-onset hypothyroidism in cockatiels was created by radiothyroidectomizing cockatiels with 3.7 MBq (100 μCi) of 131I/bird given IV. Induction of the hypothyroid state was confirmed by baseline T4 concentration, tsh response test results, thyroid pertechnetate scintigraphy, and gross and microscopic examinations. Classical signs of hypothyroidism (eg, hypercholesterolemia, obesity, poor feathering) were lacking or mild at 48 days after thyroid ablation.

Pharmacokinetic Properties of Gentamicin and Amikacin in the Cockatiel

Gentamicin and amikacin are commonly used in veterinary medicine to treat a variety of gram-negative bacterial infections. The present study evaluates the pharmacokinetics of gentamicin sulfate and amikacin sulfate in the cockatiel (Nymphicus hollandicus), a small (approximate body weight = 100 g) psittacine bird, utilizing treatment regimens developed in larger parrot species. Serum antibiotic concentrations were determined in cockatiels following twice-daily intramuscular treatment with 5 mg gentamicin/kg body weight and 15 mg amikacin/kg body weight. In the present study, peak values of gentamicin were 4.6 +/- 1.45 micrograms/ml, and trough values were 0.17 +/- 0.04 micrograms/ml. Amikacin administration resulted in peak values of 27.3 +/- 6.9 micrograms/ml and trough concentrations of 0.9 +/- 0.3 micrograms/ml. Based on the present study, an appropriate intramuscular dose regimen for gentamicin in cockatiels is 5 to 10 mg/kg body weight either two or three times per day. An intramuscular amikacin dosage of 15 to 20 mg/kg body weight either two or three times per day is recommended for treatment of infections caused by susceptible bacteria.

Eye lesions in pet birds

Amongst eye lesions in birds that died in quarantine, cataracts were the most common disorders (37/241, 15.4%), being prevalent in the annular pads of cockatiels (Nymphicus hollandicus), Amazon parrots (Amazona aestiva aestiva) and budgerigars (Melopsittacus undulatus). The incidence in male birds was more than twice that in females. Deposition of crystals, mostly in the cornea, was the second most frequent lesion (21/293, 8.7%), mainly found in cockatiels, parakeets (Psittacula krameri manillensis), Amazon parrots (Amazona aestiva aestiva), budgerigars and finches (Poephila gouldiae gouldiae). These corneal crystals were negative to PAS and Kossa's stains. Six parakeets (Psittacula krameri manillensis) had calcium salts deposited in the inner plexiform layer of the retina and occasionally in the iris and ciliary body. Neither inflammation nor neo-vascularization was observed when cataracts, corneal crystalline deposition, and retinal and ciliary calcification were present. Intranuclear inclusion bodies typical for papovavirus infection were found in the eyelids of six budgerigars (2.5%). Similar inclusions were simultaneously found in the pars ciliaris retinae (4, 1.7%), inner plexiform of retina (1, 0.4%) and anterior epithelium of the cornea (1, 0.4%). Other lesions such as candidial endophthalmitis, conjunctival cryptosporidiosis, corneal dystrophy, keratitis, corneal perforation and iridocyclitis, were occasional findings.

Herpesvirus infections in psittacine birds in Japan

Herpesvirus infection was diagnosed histologically and electron microscopically in 21 out of 241 pet birds examined. The infected birds included 14 parakeets (Psittacula krameri manillensis) with respiratory infection and three parrots (Ama-zona aestiva aestiva), two cockatiels (Nymphicus hollandicus) and two rosellas (Platycercus emimius) with Pacheco's disease. The consistent lesions of respiratory herpesvirus infection were the formation of syncytial cells associated with the presence of intranuclear inclusion bodies, mainly in the lung and air sac. There was lack of an apparent cellular reaction in situ. The agent induced tubular structures containing a clear core in the nuclei of the affected cells. The present study indicated that it was a distinct entity from infectious laryngotracheitis based on tissue tropism, host reaction and morphology of the tubular structures. The striking lesions of Pacheco's disease consisted of syncytial cell formation with intranuclear inclusion bodies in various organs, especially the liver, parathyroid, ovary, bone marrow and intestine. This agent showed similar morphology to that of the respiratory herpesvirus infection, but was larger in size and had no tubular structure formation in the nuclei of affected cells.

Histologic and immunohistochemical studies of granular cell tumors in seven dogs, three cats, one horse, and one bird.

In a retrospective study, granular cell tumors in six dogs (Nos. 1-6), three cats (Nos. 1-3), one horse (No. 1), and one cockatiel (Nymphicus hollandicus) (No. 1) and a meningioma with a granular cell component in one dog (No. 7) were examined histologically and immunohistochemically. These tumors were identified by histologic examination of surgical biopsy specimens, except in the horse, in which the tumor was an incidental finding at necropsy. These diagnoses were initially made by more than one pathologist. Five of the six granular cell tumors in the dogs were in the oral cavity; one of these was in the maxillary gingiva of a 6-month-old puppy. The tumors in the cats were located in the tongue, vulva, and digit. The tumor in the horse was in the lung, and the tumor in the cockatiel was in the periocular tissue. Histologically, all granular cell tumors were characterized by oval to polygonal cells of various sizes. The cells had abundant, pale, eosinophilic cytoplasm with distinct intracytoplasmic granules, distinct cell margins, and mostly central nuclei. In the dogs, the gingival tumor had a large amount of collagen tissue, the tumor in the tongue had dilated blood vessels, and the maxillary tumor in the puppy was more cellular than the other tumors. The tumors in the cats were more anaplastic than the other tumors; one, located in the digit, was considered malignant. The granules in all of the tumors stained with periodic acid-Schiff and were diastase resistant. On staining with Luxol fast blue, the granules of all tumors stained different shades of pink, with the exception of the tumor in the tongue of a cat, which stained bluish green. Immunocytochemically, all tumors except the tumor in the cockatiel reacted against antibodies to vimentin. The granular cell tumor in the lung of the horse and the intracranial meningioma in a dog reacted to the antibody S-100 protein; the tumor in the horse reacted to neuron-specific enolase; tumors in two dogs (gingiva and skin) reacted to L-antitrypsin, and the maxillary tumor also reacted to lysozyme; the malignant tumor in the digit of a cat and the periocular tumor in the cockatiel reacted to muscle common actin and actin; the tumor in the cockatiel also reacted to desmin. Results of these immunocytochemical studies suggest that granular cell tumors, like tumors composed of rhabdoid cells, clear cells, and oncocytes, can have similar morphologic features but be of different cellular origins.

Peahens lay more eggs for peacocks with larger trains

Reproduction is costly and individual decisions about when and how much to invest in reproduction will relate to potential benefits in terms of offspring survivorship or mating success. For those organisms that can reproduce more than once, individuals should invest relatively more in reproduction when the potential benefits are high. If females gain directly or indirectly from choosing attractive, highly ornamented males, then it could be predicted that females mated to these males should invest more in reproduction. Here we report the first test of this prediction for a lekking species, peafowl (Pavo cristatus), in which males do not provide resources for offspring, and females prefer to mate with those males that possess the most elaborate trains. We find that peahens randomly mated to males that vary in the degree of ornament produce more eggs for those peacocks with more elaborate trains. We could find no evidence to support the possibility that this difference arises as a result of difference between males in their ability to fertilize eggs.

Occurrence of Velogenic Viscerotropic Newcastle Disease in Pet and Exotic Birds in 1991

In 1991, velogenic viscerotropic Newcastle disease (VVND) was diagnosed in domestic psittacine birds in six states: Illinois, Indiana, Michigan, Texas, California, and Nevada. In the first four states, the disease assumed outbreak proportions. The affected psittacine birds--yellow-headed Amazon parrots (Amazona ochrocephala oratrix), yellow-naped Amazon parrots (Amazona ochrocephala auropalliata), cockatiels (Nymphicus hollandicus), and conures (unknown species)--exhibited respiratory and/or central nervous system signs. The velogenic viscerotropic Newcastle disease virus (VVNDV) was isolated from cloacal and tracheal swabs and various tissues, such as the lung, trachea, distal intestine, and spleen. The origin of the birds could not be established. The disease in the six states was promptly controlled, with no evidence that domestic poultry had been exposed. Also, VVNDV was isolated from quarantined birds intended for importation into the United States. Included were 53 moustached parakeets (Psittacula alexandri fasciata), a mynah (Gracula religiosa), a drongo (Dicrurus sp.), and three partridges (family Phasianidae). Groups of birds that yielded VVNDV were denied entry into the United States. Birds that are illegally imported and therefore not tested for the presence of foreign animal pathogens are a potential source of VVNDV and a threat to domestic poultry and caged birds.

Health risks of housing small psittacines in galvanized wire mesh cages

Summary Each week over a 6-week period, 80 adult cockatiels (Nymphicus hollandicus) of either gender were dosed orally with fine particles of pure zinc or galvanized coating removed from welded wire mesh. At dosage of 32 mg/wk, all birds became severely ill and either died or were euthanatized within 2 weeks. Dosage of 2 mg/wk induced chronic illness marked by dullness, weight loss, and intermittent excretion of greenish droppings. Necropsy findings were unremarkable, except for signs suggestive of impaired gastrointestinal tract motility and histologic degenerative changes associated with focal mononuclear infiltration in the liver, kidneys, and pancreas. Tissue, especially pancreatic, contents of zinc were markedly high. Pure zinc was as toxic as galvanizing zinc. White rust, an oxidation product, also was toxic. The galvanized coating on cages and flights must be carefully wire-brushed and examined before housing psittacine birds.

Pituitary Adenoma in a Cockatiel (Nymphicus hollandicus)

MICHELLE CURTIS-VELASCO graduated summa cum laude from the University of Florida in 1974 with a BS in zoology and received her DVM degree from Auburn University in 1978. She participated in a student externship at the St. Louis Zoo. After serving for two years as staff veterinarian at the Jacksonville, Florida zoo, she went into private practice in Jacksonville and began seeing companion birds because she was the only exotic practitioner in town. In 1985, she associated with the All Animal Clinic in Middleburg, Florida. Since 1988, she has owned her own clinic where she does primarily avian work. 104-gram, four-year-old pied Cockatiel hen (Nymphicus hollandicus) A as referred for evaluation with a three-week history of polyuria and lethargy. The bird had produced young during the previous two breeding seasons, but had failed to lay eggs prior to presentation. Radiographs taken by the referring veterinarian were nondiagnostic. There was no evidence of glucosuria using a urine dipstick,a and the urine specific gravity was 1.005. Intestinal parasites could not be demonstrated using direct and wet mount flotation techniques. Choanal cultures indicated the presence of a nonhemolytic staphylococcus and light growth of candida, while cloacal cultures revealed a nonhemolytic staphylococcus and bacillus. Hematology showed a packed cell volume (PCV) of 55%, estimated white blood cell (WBC) count of 4,000 -6,000, elevated total solids at 6.Og/dl (normal = 2.2 5.0 measured on the refractometer), and a slight eosinophilia at 5% of the total WBC. The bird was treated with nystatin suspension (0.3 ml b.i.d.) and an electrolyte 6 solution orally. At the time of discharge, the owner mentioned that a few orange feathers had grown outside the normal cheek patch on the side of the head (Fig. 1). Three days later, the bird had not improved. A fecal sample was sent to the Florida State Diagnostic Laboratory for virus isolation, and the bird was started on doxycycline oral suspension 20 mg/kg b.i.d. Three weeks later the Cockatiel was returned for evaluation. The bird was cachectic (87 g), had dilated pupils and appeared dazed and blind. The orange spot on the cheek had lost definition and orange feathers were appearing sporadically over the entire head region (Fig. 2). The possibility of cerebral neoplasia was discussed. However, the owner mentioned the potential for heavy metal exposure, and therapy with calcium EDTA (3 mg IM b.i.d.) was initiated. The bird appeared to improve slightly over the next two days, but subsequently regressed and died. The necropsy revealed a 5 mm mass in the area of the pituitary gland compressing the adjacent brain parenchyma. Histopathology confirmed a pituitary adenoma.

Compounded Doxycycline in Budgies and Cockatiels

Compounded Doxycycline in Budgies and Cockatiels

Reproductive behavior and LH levels of cockatiels ( Nymphicus hollandicus) associated with photostimulation, nest-box presentation, and degree of mate access

To determine the relative contribution of mate access and environmental cues in stimulating egg-laying and plasma luteinizing hormone (LH) secretion in cockatiels ( Nymphicus hollandicus), and of mate access on nest-inspection and bowl-formation, mated pairs were permitted different degrees of mate access (full contact, auditory plus visual contact, auditory contact only, or no contact) and sequentially exposed to three environmental conditions (8L:16D without nest-box access for 6 weeks; 15L:9D without nest-box access for 3 weeks; 15L:9D with nest-box access for 3 weeks). The results indicate that a high degree of mate access is essential for the performance of nesting behaviors, since birds allowed no mate access or only auditory mate access were significantly less likely to inspect the nest or form a nest-bowl. Furthermore, pairs permitted no contact, auditory contact only, or auditory and visual contact delayed nest-inspection and bowl-formation and were significantly less likely to lay eggs than pairs with total mate contact. LH levels were significantly elevated only in photostimulated females of pairs of permitted full mate and nest-box access. These results suggest that maximal sexual activity in cockatiels requires an array of behavioral and environmental cues and that a linear relationship exists between extent of social cues and sexual activity.

Plasma LH and prolactin levels during the reproductive cycle of the cockatiel ( Nymphicus hollandicus)

Plasma-luteinizing hormone (LH) and prolactin (Prl) levels were determined using radioimmunoassay during two reproductive cycles in captive cockatiels ( Nymphicus hollandicus)—an altricial species in which both parents share incubation and care of young. Birds were stimulated to breed by increasing daylength, light intensity, ambient temperature, and presenting nest boxes. LH levels were elevated during the time of nest inspection in females and peaked during egg laying. In contrast, LH levels were highest in males during nest inspection but were lower during egg laying. In both sexes, LH continued to decline during incubation and care of the young but rose in pairs laying a second clutch. Female and male Prl levels increased during egg laying, peaked during incubation, then declined to egg-laying levels during the nestling stage. Prl continued to decline during the fledgling stage and reached prelaying levels unless a second clutch was begun. In conclusion, in cockatiels, nest inspection and laying are characterized by high LH levels while high Prl levels occur during incubation and feeding of nestlings in both males and females.

Reproductive Activity of Force-Paired Cockatiels (Nymphicus hollandicus)

Reproductive Activity of Force-Paired Cockatiels (Nymphicus hollandicus)