Rhynchopsitta Pachyrhyncha Research Articles

Spatial behaviors and seasonal habitat use of the increasingly endangered thick-billed parrot (Rhynchopsitta pachyrhyncha)

The thick-billed parrot (Rhynchopsitta pachyrhyncha) inhabits highland pine forests in the Sierra Madre Occidental ranges of northwestern Mexico. Their populations have declined significantly to < 2000 individuals due to habitat loss, illegal hunting and increasing predation. Despite their ecological and cultural importance and increasingly endangered status, the species is data deficient. Our study aimed to inform and enhance conservation management strategies for thick-billed parrots with information on their spatial ecology, habitat use, migratory behaviors and social associations. We deployed biotelemetry devices to conduct the first tracking study of wild thick-billed parrots. Our study revealed that thick-billed parrots are seasonal migrators, departing their breeding habitats around October and returning from southern habitats around April. Our research also identified previously unknown overwintering sites and migratory stopover locations, as well as a new nesting site. The parrots exhibited high spatial variability in range shifting behavior, but all tracked parrots exhibited range shifts during migration, with durations of 3–181 days and distances of 173–765 km. They traveled in close social groups and migratory routes primarily followed high-elevation forests along the Sierra Madre Occidental ranges. Home range analysis indicated smaller breeding site ranges and larger overwintering ranges, possibly reflecting nesting constraints and winter food resource dispersion. Parrot spatial associations favored high-elevation forest landscapes with tall and wide-trunked trees, underscoring the importance of preserving old-growth forests for nesting and foraging. Less than 20% of parrot habitats have formal regulatory protections. Conservation management efforts must focus on increasing protections for nesting areas, overwintering habitats, and key migratory stopover sites. As climate change exacerbates regional threats, integrated management plans involving local stakeholders and communities are essential for the parrots' long-term survival and the preservation of their old-growth forest habitats.

An ancient Thick-billed Parrot (Rhynchopsitta pachyrhyncha) from southeastern New Mexico with a review of archaeological occurrences in the American Southwest

Los sitios arqueológicos del suroeste norteamericano contienen restos de loros y guacamayas (Psittacidae). Las distribuciones remanentes de estas especies se ubican en el sur, en México y Centroamérica. Por ello, la presencia arqueológica de psitácidos en el suroeste norteamericano se ha interpretado como producto de interacciones culturales de larga distancia con Mesoamérica. Sin embargo, a diferencia de la ecología tropical de otras especies encontradas en sitios del suroeste, las cotorras serranas occidentales (Rhynchopsitta pachyrhyncha) son especialistas en conos de pinos que se encuentran en bosques de coníferas a grandes elevaciones. La ecología y la historia natural de esta especie sugiere que las cotorras serranas arqueológicas podrían haber sido obtenidas de poblaciones presentes naturalmente en el suroeste norteamericano. Aquí documento un nuevo registro de cotorra serrana occidental del sitio Bonnell en New Mexico y describo características osteológicas que permiten distinguir esta especie de otros psitácidos. A continuación reseño el registro arqueológico para explorar la hipótesis sobre la procuración regional vs. extra-regional de cotorras serranas por culturas del suroeste. Se conocen restos esqueléticos de cotorras serranas en 10 sitios arqueológicos en Arizona y New Mexico, fechados entre ∼600–1400 D.C. Los sitios con cotorras serranas se encuentran localizados al interior o cerca de bosques montanos de coníferas y/o los habitantes de esos sitios estaban involucrados en actividades económicas o de subsistencia que los conectaban con bosques montanos regionales. El contexto climático en algunos sitios sugiere que la utilización de recursos del bosque por los pueblos del pasado coincidió con periodos potenciales de buena producción de conos de pinos. En el siglo XX, parvadas históricas y reintroducidas visitaron muchos de los mismos bosques, o que demuestra la capacidad de esos bosques para albergar cotorras serranas. La relación entre cotorras serranas arqueológicas y hábitats viables apoya el modelo de procuración regional. Las cotorras serranas occidentales probablemente estuvieron presentes en el suroeste norteamericano, al menos estacionalmente, a lo largo del Holoceno tardío, un hallazgo con implicaciones para la conservación de esta especie críticamente en peligro. Palabras clave: biogeografía, extirpación, migración, Psittacidae, zooarqueología.

Nutrition of free-living Neotropical psittacine nestlings and implications for hand-feeding formulas.

Psittacidae is one of the most endangered families of birds in the world. Knowledge of their nutrition is important for understanding their survival and productivity in the wild, as well as for their adequate husbandry under human care. Hand-rearing is a common practice for psittacines, however research on their nutrition is limited. We analysed the predicted metabolisable energy, crude protein, crude fat, mineralsand the essential amino acid profiles of the crop contents from free-living nestlings of scarlet macaws (Ara macao) and red-and-green macaws (Ara chloropterus) from southeastern Peru, Cuban Amazons (Amazona leucocephala bahamensis) from the Bahamas, lilac-crowned Amazons (Amazona finschi) from northwestern Mexicoand thick-billed parrots (Rhynchopsitta pachyrhyncha) from northern Mexico. The crop content of the different parrot species displayed remarkably similar nutritional profiles, considering their diversity in habitats, geographic rangesand food sources. The crude protein and crude fat concentrations in crop samples were particularly similar for the Ara and Amazona species, while the thick-billed parrot stood out for its higher crude fat and lower crude protein content. Wider variations were found among the concentrations of sodium (Na) and iron (Fe), prolineand tryptophan. Compared with the requirements of 6-12weeksleghorn chickens, all free-ranging parrot diets contained lower crude protein, calcium (Ca), potassium (P)and Na concentrations. The hand-feeding formulas contained lower crude fat, magnesium (Mg), arginine, valine and phenylalanine concentrations, as well as much higher levels of Ca and zinc (Zn), in comparison with parrot crop samples. Our data suggest that a single formulation could be used to hand-rear Ara and Amazona sp. of 3weeks of age and older, while a different formulation would likely be more appropriated for Rhynchopsitta sp. Experimental studies should evaluate if increasing the concentration of crude fat, Mg, arginine, valineand phenylalanine enhances psittacine chick growth and health.

Genetic Diversity and Population Structure of Two Endangered Neotropical Parrots Inform In Situ and Ex Situ Conservation Strategies

A key aspect in the conservation of endangered populations is understanding patterns of genetic variation and structure, which can provide managers with critical information to support evidence-based status assessments and management strategies. This is especially important for species with small wild and larger captive populations, as found in many endangered parrots. We used genotypic data to assess genetic variation and structure in wild and captive populations of two endangered parrots, the blue-throated macaw, Ara glaucogularis, of Bolivia, and the thick-billed parrot, Rhynchopsitta pachyrhyncha, of Mexico. In the blue-throated macaw, we found evidence of weak genetic differentiation between wild northern and southern subpopulations, and between wild and captive populations. In the thick-billed parrot we found no signal of differentiation between the Madera and Tutuaca breeding colonies or between wild and captive populations. Similar levels of genetic diversity were detected in the wild and captive populations of both species, with private alleles detected in captivity in both, and in the wild in the thick-billed parrot. We found genetic signatures of a bottleneck in the northern blue-throated macaw subpopulation, but no such signal was identified in any other subpopulation of either species. Our results suggest both species could potentially benefit from reintroduction of genetic variation found in captivity, and emphasize the need for genetic management of captive populations.

SARCOCYSTOSIS IN A CAPTIVE FLOCK OF THICK-BILLED PARROTS (RHYNCHOPSITTA PACHYRHYNCHA) FROM 2005 TO 2016: MORBIDITY, MORTALITY, DIAGNOSTICS, AND MANAGEMENT STRATEGIES

Sarcocystosis was diagnosed in a captive flock of thick-billed parrots (Rhynchopsitta pachyrhyncha) at the Wildlife Conservation Society's Queens Zoo. Since the index case in 2005, 45% of mortalities in birds over 30 days of age were due to sarcocystosis. Sarcocystis falcatula was repeatedly identified as the causative agent. The disease predominantly affected younger adult parrots. Administration of antiparasitic medications prior to development of respiratory signs prolonged life in infected birds, but disease was fatal until utilization of a three-drug combination (pyrimethamine, trimethoprim-sulfamethoxazole, and ponazuril). This protocol may require in excess of 6 mo of therapy to achieve clinical resolution of active disease. Plasma creatine kinase activity was found to be the most useful test in diagnosing infection and monitoring response to therapy. Polymerase chain reaction (PCR) for apicomplexan organisms on antemortem whole blood, blood smears, or dried blood spots helped confirm suspected cases, but due to the poor sensitivity was sometimes misleading when assessing response to therapy or resolution of clinical disease. Preventive measures, focusing on exclusion and removal of Virginia opossums (Didelphis virginiana) from zoo grounds failed to curtail the occurrence of sarcocystosis in the flock. Other preventative steps, such as modification of feeding stations to exclude potential arthropod paratenic hosts and prophylaxis trials with diclazuril, appeared to successfully mitigate new infections. Given the diagnostic and therapeutic challenges, prevention of exposure to S. falcatula is essential to ex-situ conservation efforts for thick-billed parrots.

Predation of nesting Thick-billed Parrots Rhychopsitta pachyrhyncha by bobcats in northwestern Mexico

SummaryWe report on what appear to be increasing predation events on nesting Thick-billed Parrots Rhychopsitta pachyrhyncha. Thick-billed Parrots are classified as ‘Endangered’ and their seasonal breeding range is restricted to increasingly fragmented and degraded high elevation mixed conifer forest habitat within the Sierra Madre Occidental region of north-western Mexico. Predation of established breeding pairs has recently contributed to the ongoing decline of Thick-billed Parrot populations by removing mature birds with high reproductive value, which has associated consequences for future recruitment. We observed increasing predation events on nesting Thick-billed Parrots by bobcats Lynx rufus accompanied by kittens throughout the 2018–2019 breeding seasons, and we speculate that recent reductions in bobcat habitat have pushed them into new ranges where they are supplementing their diet with nontraditional prey items.

Fatty acid profiles of crop contents of free-living psittacine nestlings and of commercial hand-feeding formulas.

Research on psittacine nutrition is limited, and nestling requirements are poorly understood. This study analysed fatty acid (FA) profiles of crop contents of free-living scarlet macaws (Ara macao, n=18), red-and-green macaws (Ara chloropterus, n=5), Cuban parrots (Amazona leucocephala bahamensis, n=27), lilac-crowned Amazons (Amazona finschi, n=33) and thick-billed parrots (Rhynchopsitta pachyrhyncha, n=32). The same analysis was carried out on 15 commercial parrot hand-feeding formulas. The mean FA concentration of the crop samples of each species ranged from 15% to 53% DM for crop samples and ranged from 6% to 22% for hand-feeding formulas. Long-chain FA represented over 92% of all FA in the crop samples and over 81% of all FA in the commercial formulas. Parrot species shared similarities in saturation profiles of crop samples, ranging between 13%-29% saturated fatty acids (SFA), 12%-40% monounsaturated fatty acids (MUFA) and 39%-58% polyunsaturated fatty acids (PUFA). All studied psittacines, except for the red-and-green macaw, were within the range of values for hand-rearing formulas. Palmitic acid was the most common SFA in scarlet macaws, red-and-green macaws, Cuban parrot, thick-billed parrot and in all but one commercial formula. Palmitic and stearic acids dominated the SFA in the samples of the Lilac-crowned Amazon. Oleic acid was the most common MUFA in all hand-feeding formulas as well as in the crop samples, except for the lilac-crowned amazon and the thick-billed parrot where vaccenic acid dominated. Linoleic acid was by far the most common PUFA found in the crop samples as well as in the hand-feeding formulas. PUFA were largely dominated by the n6 family, both in the crop samples and the formulas. The data presented on nestling diets of free-living parrot species provide a foundation for future researchers to test whether increasing FA concentration in hand-feeding formulas improves nestling development or if species-specific formulas will be advantageous.

Status of naturalized parrots in the United States

The contiguous United States (USA) originally had two endemic parrot species, the Carolina Parakeet (Conuropsis carolinensis) and the Thick-billed Parrot (Rhynchopsitta pachyrhyncha). The Carolina Parakeet is now globally extinct, and the Thick-billed Parrot was extirpated from the USA. Otherwise, over the last century, the USA has become home to an increasing number of naturalized parrots, originally introduced through the pet trade. In this paper, we use historical records as well as data from citizen science (eBird and Christmas Bird Count, CBC) to summarize the current status of each of the naturalized parrots in the USA. During the 15-year period 2002–2016, eBird and CBC contain sighting records of 56 species of parrots in the wild in 43 states. Of these, 25 species are now breeding and 23 states have at least one species of parrot breeding there. The three most common species are the Monk Parakeet (Myiopsitta monachus), the Red-crowned Amazon (Amazona viridigenalis), and the Nanday Parakeet (Aratinga nenday). Collectively, these three species comprise a total of 61% of all sightings on eBird and CBC over the last 15 years. Three states—Florida, Texas, and California—collectively support populations of all 25 species of breeding parrots in the USA. Naturalized parrots are now common species in local avifaunas in many areas in the USA, and they highlight complex issues, from the conservation of endangered species to the management of invasive species.

Cuatro siglos de variabilidad hidroclimática en el noroeste de Chihuahua, México, reconstruida con anillos de árboles

A Douglas-fir chronology with a length of 409 years (1600-2008) was developed for northwestern Chihuahua in Mesa de las Guacamayas, a “Natural Protected Area” known as an important nesting habitat for the thick-billed parrot (Rhynchopsitta pachyrhyncha) an endangered neotropical bird. Increment cores and cross-sections from selected Douglas-fir trees (Pseudotsuga menziesii) in a mixed conifer forest were obtained with an increment borer and a chain-saw. Standard dendrochronological techniques were used to process and date each one of the rings to their exact year of formation. The quality of dating of the measured series was analyzed with the COFECHA program, while biolo-gical trends not related to climate (age differences, stem-size increases, and disturbances) were removed by standardiza-tion procedures in the ARSTAN program. Tree ring series of earlywood, latewood and total ring width were developed for the last four centuries. The total ring-width chronology was significantly associated (r>0.40, p=0.000) with nearby chronologies, particularly those located <200 km apart along the western slopes of the Sierra Madre Occidental (SMO) observing correlations as high as 0.69 (p<0.001). Association between chronologies decreased for those sites in the state of Durango along the SMO but separated more than 200 km in straight line and also for sites in nearby borderline in the USA side. The similar climatic response among distant chronologies implies the influence of common atmospheric circulatory patterns affecting a large portion of land simultaneously. ENSO is one of the most important factors in determining inter-annual and multiannual hydroclimatic variability in northern Mexico, increasing winter-spring precipitation in its warm phase and causing extreme droughts in its cold phase. A negative relationship (r=-0.4, n= 106, p<0.0000) was found between average January-May Southern Oscillation Index (SOI) and earlywood indices corroborating the significant influence of ENSO in cool season precipitation for this region. A power spectral analysis of the seasonal winter-spring precipitation reconstruction detected the presence of significant peaks (p<0.05) <10 years (5, 10 years) commonly associated to ENSO. Significant frequencies at 50 and near 100 years have also been related to the ENSO influence. 50-year frequency droughts historically have caused intense and prolonged droughts in northern and central Mexico, particularly those in the periods 1613-1617, 1666-1673, 1728-1733, 1752-1761, 1840-1845, 1862-1866, 1934-1939, 1944-1951, and 1953-1957. The ring-width index values were significantly associated (r=0.52, n=1 11, p<0.000) with PDSI values recorded for the Southwestern region of the USA. The PDSI integrates precipitation and temperature data and is a measure of the availability of moisture for tree growth as related to average moisture conditions. The relationship between PDSI data from Arizona and New Mexico and ring-width indices from Mesa de las Guacamayas, Chihuahua is an indication that extreme climatic events extend from the Southwestern USA to northern Chihuahua and even further down in the Durango state. This behavior highlights the im-portance of developing a network of three ring chronologies at basin or watershed level to have a better understanding of climate dynamics. A seasonal January-July precipitation reconstruction detected intense and prolonged droughts for the periods1772-1782, 1793-1803, and 1999-2008, where 1633 and 1954 stand out as the driest years of the reconstruction. Wet episodes were detected from 1742 to 1751 and from 1809 to 1818. Pluvials are less recorded in historical documents and tree rings are less sensible to wet episodes given that much of the precipitation for this region takes place in the summer months when earlywood formation that makes most of the ring size has ceased. In addition, much of the rain is lost by runoffas its intensity exceeds soil infiltration rate and water holding capacity of the soil is overridden. Historical droughts have had a seve-re impact in food production, reducing grain availability, increasing livestock mortality, and producing famine. The drought documented for the period 1613 to 1626 has been detected in Durango, Chihuahua and New Mexico. Later droughts like one in the 1720's, end of the 1730's and early part of the 1740 ’s produced grain scarcity and famine in a great portion of northern Mexico. The drought of the 1950 s extended all over northern Mexico and southwestern USA producing economical crisis in rural areas and greatly increased immigration and movement of migrant farm workers (braceros) to the USA. The proportion of dry years detected in the reconstruction suggests a 50% probability of occurrence of below average precipitation for a given year, implying that the development of a more extensive network of climate sensitive tree-ring chronologies will allow us a better understanding of climate variability in this region which is important for the management of limited water resources and for the conservation of endangered wildlife species.

Complete mitochondrial genome of endangered Maroon-fronted Parrot (Rhynchopsitta terrisi) – conspecific relation of the species with Thick-billed Parrot (Rhynchopsitta pachyrhyncha)

Maroon-fronted Parrot (Rhynchopsitta terrisi) is an endangered parrot endemic to pine-oak forests in north-eastern Mexico. According to all present classifications, R. terrisi as well as Rhynchopsitta pachyrhyncha are treated as a separate species based on some morphological and behavioral discrepancies. Despite this formal separation of the two species, some taxonomists conjecture their conspecific character. However, mutual taxonomic position of both species/subspecies was never verified by molecular research. We sequenced full mitochondrial genome of R. terrisi and constructed phylogenetic tree using sequences of mitochondrial ND2 gene from R. terrisi. R. pahyrchyncha and some other representative species of the tribe Arini. Our results indicated that in contrast to formal classification, both Rhynchopsitta taxa should be treated as subspecies.

Determination of the minimum anesthetic concentration of sevoflurane in thick-billed parrots (Rhynchopsitta pachyrhyncha)

To determine the minimum anesthetic concentration (MAC) of sevoflurane in thick-billed parrots (Rhynchopsitta pachyrhyncha) and compare MAC obtained via mechanical and electrical stimulation. 15 healthy thick-billed parrots. Anesthesia was induced in each parrot by administration of sevoflurane in oxygen. An end-tidal sevoflurane concentration of 2.5% was established in the first bird. Fifteen minutes was allowed for equilibration. Then, 2 types of noxious stimulation (mechanical and electrical) were applied; stimuli were separated by 15 minutes. Responses to stimuli were graded as positive or negative. For a positive or negative response to a stimulus, the target end-tidal sevoflurane concentration of the subsequent bird was increased or decreased by 10%, respectively. The MAC was calculated as the mean end-tidal sevoflurane concentration during crossover events, defined as instances in which independent pairs of birds evaluated in succession had opposite responses. A quantal method was used to determine sevoflurane MAC. Physiologic variables and arterial blood gas values were also measured. Via quantal analysis, mean sevoflurane MAC in thick-billed parrots determined with mechanical stimulation was 2.35% (90% fiducial interval, 1.32% to 2.66%), which differed significantly from the mean sevoflurane MAC determined with electrical stimulation, which was 4.24% (90% fiducial interval, 3.61% to 8.71%). Sevoflurane MAC in thick-billed parrots determined by mechanical stimulation was similar to values determined in chickens and mammals. Sevoflurane MAC determined by electrical stimulation was significantly higher, which suggested that the 2 types of stimulation did not induce similar results in thick-billed parrots.

Evaluation of Antibody Response to Vaccination Against West Nile Virus in Thick Billed Parrots (Rhynchopsitta pachyrhyncha)

West Nile virus (WNV) was first documented in North America in New York City in 1999. Several deaths attributable to WNV have been reported in captive thick-billed parrots (Rhynchopsitta pachyrhyncha), an endangered psittacine native to North America. The serologic responses in 12 captive adult thick-billed parrots after a series of three initial WNV vaccine injections with annual boosters over 6 yr was evaluated. In addition, the serologic responses of 11 thick-billed parrot chicks following an initial vaccination series to determine if there were seroconversions were also reported. Most adults (67%) had seroconverted after 5 yr of annual vaccination, with a median titer of 1:80 (range 1:40-1:160) for those that seroconverted. After the first year, birds were likely naturally exposed to WNV, which limited interpretation of titers. None of the chicks seroconverted during the initial three-vaccine series; only two of four chicks (50%) had seroconverted when tested at the 1-yr yearly booster, and at 2 yr, three of four chicks had seroconverted. Although some birds had detectable antibody titers, it is unclear whether this vaccine can reliably provide protection against WNV in thick-billed parrots.

Radiation Therapy of a Malignant Melanoma in a Thick-billed Parrot (Rhynchopsitta pachyrhyncha)

A male thick-billed parrot (Rhynchopsitta pachyrhyncha) was diagnosed with a malignant melanoma of the mandibular beak (gnathotheca). Surgical excision was impossible because of the location of the lesion; a combination of radiation therapy and oral antitumor drugs were used to treat the neoplasm. A whole-body computed tomographic scan showed evidence of metastasis in the lungs; the bird, therefore, was considered to have stage IV disease. Throughout the treatment period, the bird showed no clinical evidence of systemic disease. The bird was given 20 treatments of localized radiation therapy of 2.5 Gray (Gy) for a cumulative dose of 50 Gy. The bird was also treated with piroxicam and cimetidine orally from the time of diagnosis, throughout radiation therapy, and until its death. By the completion of radiation therapy, the initial lesion had decreased considerably in size. The bird survived 2.5 months after radiation therapy was completed but died of complications related to metastatic disease. Necropsy results revealed metastases throughout the body, including lesions in the lungs and liver. To our knowledge, this is the first report of localized radiation therapy and oral antitumor drugs being used to treat malignant melanoma in an avian patient. The radiation therapy did produce tumor response in the form of a reduction in size of the visible tumor.

Avian Plasma Chemistry Analysis Using Diluted Samples

Clinical chemistry tests are essential for the diagnosis and monitoring of disease in birds. The small volume of blood that can be obtained from many avian species limits the use of routine in-house chemistry analyzers. The aim of this study was to examine the accuracy and precision of avian plasma chemistry values obtained by use of a benchtop analyzer in samples diluted with sterile water, as compared with undiluted samples. Whole blood samples were collected from 13 clinically healthy thick-billed parrots (Rhynchopsitta pachyrhyncha). The samples were placed in lithium heparin tubes and centrifuged and the plasma decanted. One aliquot was analyzed immediately using a VetScan benchtop analyzer with an avian-reptile-specific rotor that included 12 analytes. The remainder of the plasma was divided into two aliquots and stored at -80 degrees C until analysis. One of these aliquots was diluted 1:1, 1:1.5, 1:2, and 1:2.5 with sterile water to give final dilutions of 1:2, 1:2.5, 1:3, and 1:3.5, respectively. The other aliquot was pooled with the 12 other samples to create a plasma pool. The undiluted plasma pool and two final dilutions (1:2 and 1:3) of the pooled plasma were analyzed in replicate (n = 20) to determine intra- and interassay imprecision. Each dilution was analyzed using the avian-reptile rotor and the results multiplied by the appropriate dilution factor to obtain the final result. Significant differences were observed in clinical chemistry results obtained from diluted plasma samples for all analytes except aspartate aminotransferase, creatine kinase, and glucose. Uric acid concentration was not significantly different at dilutions of up to 1:3. Bile acids, globulins, and sodium concentrations were below the limit of detection in all diluted samples and were not statistically analyzed. Based on these results, dilution with sterile water is not recommended for biochemical analysis of avian plasma using the VetScan benchtop analyzer.

LIMITED GEOGRAPHIC VARIATION IN THE VOCALIZATIONS OF THE ENDANGERED THICK-BILLED PARROT: IMPLICATIONS FOR CONSERVATION STRATEGIES

The populations of many species are declining worldwide, and conservation efforts struggle to keep pace with extinction rates. Conservation biologists commonly employ strategies such as translocation and reintroduction, which move individuals of endangered species from one part of their range to another. Because individuals from endangered populations are nonexpendable, identifying any potential barriers to the establishment of viable populations prior to release of individuals should be a priority. This study evaluates the potential for learned communication signals to constrain conservation strategies such as reintroduction in an endangered species, the Thick-billed Parrot (Rhynchopsitta pachyrhyncha). We conducted vocal surveys at three geographically distinct breeding populations in the Sierra Madre Occidental of Chihuahua, Mexico. Acoustic analyses utilizing both spectrogram cross-correlations and parameter measurements from spectrograms revealed no significant differences among the three sites in two common call types. Calls did vary among individuals within a site. The apparent lack of significant geographic variation across sampled sites suggests that differences in learned communication signals are unlikely to pose a barrier to the integration of translocated individuals from different populations into newly established populations.

Minimum anesthetic concentration of isoflurane in captive thick-billed parrots (Rhynchopsitta pachyrhyncha)

To determine the minimum anesthetic concentration (MAC) of isoflurane in thick-billed parrots (Rhynchopsitta pachyrhyncha). 15 healthy thick-billed parrots. Anesthesia was induced and maintained with isoflurane in oxygen. In the first bird that was anesthetized, end-tidal isoflurane concentration was maintained at 1.0% for 15 minutes. After this period of anesthetic equilibration, an end-tidal gas sample was obtained for verification of isoflurane concentration. A toe was pinched to determine the bird's response to pain, and the bird was then allowed to recover from aesthesia. To determine MAC, a so-called up-and-down approach was subsequently used in all 15 birds. Compared with the isoflurane concentration used for MAC determination in the first bird, maintenance isoflurane concentration for the second bird was increased by approximately 10% if the first bird reacted and decreased by approximately 10% if the first bird did not react to a toe pinch. These steps were then followed until all 15 birds had been anesthetized. Crossover events occurred when birds in sequence had discordant results (ie, 1 reactor and 1 nonreactor). The MAC was defined as the mean of the isoflurane concentrations measured during these crossover events. Mean MAC of isoflurane in thick-billed parrots was estimated to be 1.07% (95% confidence interval, 0.97% to 1.16%). Isoflurane MAC appears to be lower in thick-billed parrots than the MAC determined for other bird species. Determination of the species-specific requirements of thick-billed parrots should allow isoflurane anesthesia to be performed more safely in this endangered species.

GREGARIOUS NESTING BEHAVIOR OF THICK-BILLED PARROTS (RHYNCHOPSITTA PACHYRHYNCHA) IN ASPEN STANDS

Abstract We studied Thick-billed Parrot (Rhynchopsitta pachyrhyncha) nest-site density and social nesting behavior from 1998 to 2001 in Madera, Chihuahua, Mexico. The species formed high-density nesting clusters; 45 nesting attempts (30%) involved nesting pairs sharing nest trees, with a maximum of three nesting pairs per tree. The majority of nest trees were live or dead quaking aspens (Populus tremuloides). Clusters contained a mean of 11.5 breeding pairs (5 nests/ha). The highly social nesting behavior of Thick-billed Parrots may have important implications for management and conservation of their breeding habitat.

A SURVEY OF SELECTED PARASITIC AND VIRAL PATHOGENS IN FOUR SPECIES OF MEXICAN PARROTS, AMAZONA AUTUMNALIS, AMAZONA ORATRIX, AMAZONA VIRIDIGENALIS, AND RHYNCHOPSITTA PACHYRHYNCHA

Isolated populations of four species of Mexican parrots were sampled for evidence of selected pathogens of concern in birds originating in Latin America. Data were collected between June and September 1997, and ectoparasite collection was repeated with Rhynchopsitta pachyrhyncha in September 2000. Serum samples from nine Amazona oratrix, 10 Amazona viridigenalis, 6 Amazona autumnalis, and 25 R. pachyrhyncha chicks were screened for neutralizing antibodies to psittacid herpesvirus and avian influenza and for antibodies to paramyxovirus serotypes 1 and 3. Chicks were also examined visually for fecal parasites and ectoparasites. All serologic and fecal parasite tests were negative. Ectoparasites included ticks, Ixodidae; mites, Ornithonyssus sylviarum; fleas, Psyttopsylla mexicana; lice, Paragoniocotes mexicanus, Heteromenopon sp., and Psittacobrosus sp.; and bugs, Ornithocoris sp. This study provides baseline information to guide future health studies.

Feral Parrots in the Continental United States and United Kingdom: Past, Present, and Future

IntroductionIn many cities across the United States (USA),from Boston to Los Angeles and Seattle to Miami,free-flying parrots and parakeets can now be seen.Likewise, feral parakeets are now present in Eng-land in the Greater London area, on the Isle ofThanet in Kent, and in select cities along the southcoast. In some areas, these feral parrots have beenpresent for decades, whereas in others, parrots haveonly been present for a few years. This paper sum-marizes the historical changes in number and com-position of psittacine birds in the USA and UnitedKingdom (UK).Native parrot speciesThe USA was formerly home to 2 native parrotspecies—the Carolina parakeet ( Conuropsis caroli-nensis) and the thick-billed parrot (Rhynchopsittapachyrhyncha)—both of which disappeared fromthe USA during the 20th century.Carolina parakeets were formerly found through-out the southeastern USA, north to New York andwest to North Dakota, Colorado, and Texas.

Fire regime in a conservation reserve in Chihuahua, Mexico

Fire regime characteristics were reconstructed from fire-scarred trees in the Tutuaca reserve, a newly designated protected area in the Sierra Madre Occidental of western Chihuahua. The reserve was created to protect thick-billed parrot nesting habitat (large snags) and a relict forest of Chihuahua spruce (Picea chihuahuana Martínez). We collected fire-scarred samples from conifers (Pinus ayacahuite Ehrenb., Pinus durangensis Martínez, and Pseudotsuga menziesii (Mirb.) Franco) in three 25-ha sites arrayed at different watershed positions, from a low site adjacent to the spruce trees up to the watershed divide. Fire analysis periods began in 1702, 1704, or 1761 and continued through the final fire in 1955 (two sites) or 1995. All sites had frequent fire regimes (mean fire interval (MFI) 3.9–5.2 years; MFI for years in which 25% or more of the samples were scarred: 6.9–8.4 years). Almost all fires occurred before cambial growth began or early during the season of cambial growth. Fire years were significantly dry, and the years immediately preceding fire were significantly wet. After 1955, no further fires occurred at two of the three study sites, a pattern similar to that observed elsewhere in northern Mexico. The third site had fires in 1987 and 1995. The extended fire-free period in portions of the Tutuaca landscape may result in fuel accumulation and eventually in severe wildfire. For effective conservation of fire-susceptible habitat features, managers should seek to incorporate surface fire as a management tool.