Use of number by crows: investigation by matching and oddity learning.
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Hooded crows were trained in two-alternative simultaneous matching and oddity tasks with stimulus sets of three different categories: color (black and white), shape (Arabic Numerals 1 and 2, which were used as visual shapes only), and number of elements (arrays of one and two items). These three sets were used for training successively and repeatedly; the stimulus set was changed to the next one after the criterion (80% correct or better over 30 consecutive trials) was reached with the previous one. Training was continued until the criterion could be reached within the first 30 to 50 trials for each of the three training sets. During partial transfer tests, familiar stimuli (numerals and arrays in the range from 1 to 2) were paired with novel ones (numerals and arrays in the range from 3 to 4). At the final stage of testing only novel stimuli were presented (numerals and arrays in the range from 5 to 8). Four of 6 birds were able to transfer in these tests, and their performance was significantly above chance. Moreover, performance of the birds on the array stimuli did not differ from their performance on the color or shape stimuli. They were capable of recognizing the number of elements in arrays and comparing the stimuli by this attribute. It was concluded that crows were able to apply the matching (or oddity) concept to stimuli of numerical category. (+info)
Estimating the time to extinction in an island population of song sparrows.
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We estimated and modelled how uncertainties in stochastic population dynamics and biases in parameter estimates affect the accuracy of the projections of a small island population of song sparrows which was enumerated every spring for 24 years. The estimate of the density regulation in a theta-logistic model (theta = 1.09 suggests that the dynamics are nearly logistic, with specific growth rate r1 = 0.99 and carrying capacity K = 41.54. The song sparrow population was strongly influenced by demographic (sigma2(d) = 0.66) and environmental (sigma2(d) = 0.41) stochasticity. Bootstrap replicates of the different parameters revealed that the uncertainties in the estimates of the specific growth rate r1 and the density regulation theta were larger than the uncertainties in the environmental variance sigma2(e) and the carrying capacity K. We introduce the concept of the population prediction interval (PPI), which is a stochastic interval which includes the unknown population size with probability (1 - alpha). The width of the PPI increased rapidly with time because of uncertainties in the estimates of density regulation as well as demographic and environmental variance in the stochastic population dynamics. Accepting a 10% probability of extinction within 100 years, neglecting uncertainties in the parameters will lead to a 33% overestimation of the time it takes for the extinction barrier (population size X = 1) to be included into the PPI. This study shows that ignoring uncertainties in population dynamics produces a substantial underestimation of the extinction risk. (+info)
Genetic relatedness of Salmonella isolates from nondomestic birds in Southeastern United States.
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Salmonella infections have been implicated in large-scale die-offs of wild birds in the United States. Although we know quite a bit about the epidemiology of Salmonella infection among domestic fowl, we know little about the incidence, epidemiology, and genetic relatedness of salmonellae in nondomestic birds. To gain further insight into salmonellae in these hosts, 22 Salmonella isolates from diseased nondomestic birds were screened for the presence of virulence and antibiotic resistance-associated genes and compared genetically using pulsed-field gel electrophoresis (PFGE) and random amplified polymorphic DNA analysis. Of the 22 Salmonella isolates examined, 15 were positive for the invasion gene invA and the virulence plasmid-associated genes spvC and pef. Most (15 of 22) were generally sensitive to antibiotics. However, two Salmonella isolates from pet birds were identified as Salmonella enterica serovar Typhimurium DT104. Despite the general susceptibility of these Salmonella isolates to most antimicrobial agents, antibiotic resistance-associated genes intI1, merA, and aadA1 were identified in a number of these isolates. Five distinct XbaI and nine distinct BlnI DNA patterns were observed for the 22 Salmonella isolates typed by PFGE. PFGE analysis determined that Salmonella isolates from passerines in Georgia and Wyoming were genetically related. (+info)
Density-dependent decline of host abundance resulting from a new infectious disease.
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Although many new diseases have emerged within the past 2 decades [Cohen, M. L. (1998) Brit. Med. Bull. 54, 523-532], attributing low numbers of animal hosts to the existence of even a new pathogen is problematic. This is because very rarely does one have data on host abundance before and after the epizootic as well as detailed descriptions of pathogen prevalence [Dobson, A. P. & Hudson, P. J. (1985) in Ecology of Infectious Diseases in Natural Populations, eds. Grenfell, B. T. & Dobson, A. P. (Cambridge Univ. Press, Cambridge, U.K.), pp. 52-89]. Month by month we tracked the spread of the epizootic of an apparently novel strain of a widespread poultry pathogen, Mycoplasma gallisepticum, through a previously unknown host, the house finch, whose abundance has been monitored over past decades. Here we are able to demonstrate a causal relationship between high disease prevalence and declining house finch abundance throughout the eastern half of North America because the epizootic reached different parts of the house finch range at different times. Three years after the epizootic arrived, house finch abundance stabilized at similar levels, although house finch abundance had been high and stable in some areas but low and rapidly increasing in others. This result, not previously documented in wild populations, is as expected from theory if transmission of the disease was density dependent. (+info)
Horizontal flight of a swallow (Hirundo rustica) observed in a wind tunnel, with a new method for directly measuring mechanical power.
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A swallow flying in the Lund wind tunnel was observed from the side and from behind, by two synchronised high-speed video cameras. The side-view camera provided a record of the vertical position of a white mark, applied to the feathers behind and below the eye, from which the vertical acceleration was obtained. The rear-view camera provided measurements of the mean angle of the left and right humeri above horizontal. From these data, the force acting on the body, the moment applied by each pectoralis muscle to the humerus and the rotation of the humerus were estimated and used to analyse the time course of a number of variables, including the work done by the muscles in each wing beat. The average mechanical power turned out to be more than that predicted on the basis of current estimates of body drag coefficient and profile power ratio, possibly because the bird was not flying steadily in a minimum-drag configuration. We hope to develop the method further by correlating the mechanical measurements with observations of the vortex wake and to apply it to birds that have been conditioned to hold a constant position in the test section. (+info)
MHC class II pseudogene and genomic signature of a 32-kb cosmid in the house finch (Carpodacus mexicanus).
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Large-scale sequencing studies in vertebrates have thus far focused primarily on the genomes of a few model organisms. Birds are of interest to genomics because of their much smaller and highly streamlined genomes compared to mammals. However, large-scale genetic work has been confined almost exclusively to the chicken; we know little about general aspects of genomes in nongame birds. This study examines the organization of a genomic region containing an Mhc class II B gene in a representative of another important lineage of the avian tree, the songbirds (Passeriformes). We used a shotgun sequencing approach to determine the sequence of a 32-kb cosmid insert containing a strongly hybridizing Mhc fragment from house finches (Carpodacus mexicanus). There were a total of three genes found on the cosmid clone, about the gene density expected for the mammalian Mhc: a class II Mhc beta-chain gene (Came-DAB1), a serine-threonine kinase, and a zinc finger motif. Frameshift mutations in both the second and third exons of Came-DAB1 and the unalignability of the gene after the third exon suggest that it is a nonfunctional pseudogene. In addition, the identifiable introns of Came-DAB1 are more than twice as large as those of chickens. Nucleotide diversity in the peptide-binding region of Came-DAB1 (Pi = 0.03) was much lower than polymorphic chicken and other functional Mhc genes but higher than the expected diversity for a neutral locus in birds, perhaps because of hitchhiking on a selected Mhc locus close by. The serine-threonine kinase gene is likely functional, whereas the zinc finger motif is likely nonfunctional. A paucity of long simple-sequence repeats and retroelements is consistent with emerging rules of chicken genomics, and a pictorial analysis of the "genomic signature" of this sequence, the first of its kind for birds, bears strong similarity to mammalian signatures, suggesting common higher-order structures in these homeothermic genomes. The house finch sequence is among a very few of its kind from nonmodel vertebrates and provides insight into the evolution of the avian Mhc and of avian genomes generally. (+info)
Velogenic Newcastle disease in imported caged birds.
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Velogenic Newcastle disease was diagnosed in pet birds intended for importation into Canada. Virological and histopathological examination confirmed the presence of the disease. The group of birds was denied entry into Canada. Similar birds illegally imported are a potential source of velogenic Newcastle disease virus and are a threat to domestic poultry. (+info)
Divorce in cooperatively breeding long-tailed tits: a consequence of inbreeding avoidance?
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The decision of whether to divorce a breeding partner between reproductive attempts can significantly affect individual fitness. In this paper, we report that 63% of surviving pairs of long-tailed tits Aegithalos caudatus divorced between years. We examine three likely explanations for the high divorce rate in this cooperative breeder. The 'better option' hypothesis predicts that divorce and re-pairing increases an individual's reproductive success. However, divorcees did not secure better partners or more helpers and there was no improvement in their reproductive success following divorce. The 'inbreeding avoidance' hypothesis predicts that females should disperse from their family group to avoid breeding with philopatric sons. The observed pattern of divorce was consistent with this hypothesis because, in contrast to the usual avian pattern, divorce was typical for successful pairs (81%) and less frequent in unsuccessful pairs (36-43%). The 'forced divorce' hypothesis predicts that divorce increases as the number of competitors increases. The pattern of divorce among failed breeders was consistent with this hypothesis, but it fails to explain the overall occurrence of divorce because divorcees rarely re-paired with their partners' closest competitors. We discuss long-tailed tits' unique association between divorce and reproductive success in the context of dispersal strategies for inbreeding avoidance. (+info)