Tawny Owl Strix aluco response to call-broadcasting and implications for survey design

Capsule: The use of call-broadcasting significantly increases the number of Tawny Owls Strix aluco detected in winter point counts, but requires careful survey design to avoid introducing potential sources of bias into population estimates.

Aims: To examine Tawny Owl response to call-broadcasting to aid survey design in national monitoring efforts.

Methods: A nocturnal survey was undertaken at 36 survey points over three nights in winter in Thetford Forest, England. Each survey consisted of four consecutive five-minute segments: a passive count, followed by three counts with the use of call-broadcasting.

Results: Few (4%) Tawny Owls were recorded during passive surveys, whereas the greatest response was during the first and second call-broadcast segments (49% and 36%, respectively). New detections declined to 11% in the final segment. Response was fastest at dusk, although time of night did not significantly affect the number of individuals detected. Male owls accounted for 79% of detections.

Conclusion: Our results show that ten minutes of call-broadcast surveying will detect 85% of responsive Tawny Owls, thus vastly improving detection compared to passive listening alone. However, simultaneous counts of geographically separated detections should be used to provide a minimum count and reduce potential double-counting of mobile individuals.     

Population‐level dynamics in experimental mixed infections: evidence for competitive exclusion among bacterial parasites of Paramecium caudatum

Parasites frequently share their host populations with other parasites. However, little is known about how different parasites respond to competition with diverse competitor species in the within‐host and between‐host environments. We explored the repeatability of competition by simultaneously exposing microcosm populations of the ciliate Paramecium caudatum to pairs of parasites from the Holospora species complex (H. undulata, H. caryophila and H. obtusa). We measured how competition affected the persistence and prevalence of each compared to single infections, across three host genotypes. Three weeks post‐inoculation we identified the presence of each parasite using fluorescence in situ hybridisation (FISH). Competitive exclusion (62/72) was more common than co‐existence (10/72) in populations inoculated with two parasites. There was a clear pattern of competitive superiority, with H. caryophila persisting in all doubly inoculated populations (with either H. undulata or H. obtusa), and H. undulata tending to exclude H. obtusa. This mirrored infection success in single infections, with H. caryophila having a higher infection prevalence in single inoculations, followed by H. undulata then H. obtusa. The probability of persistence in co‐inoculations did not change across the different host genotypes, and prevalence was the same as in single infections. Our results are consistent with superinfection models, which assume the competitive exclusion of parasites upon contact within the same host. Furthermore, such non‐random competitive epidemiological dynamics, where one parasite always wins, may be of interest for public health management, especially if the winning parasite is avirulent, as is seemingly the case here.     

A case study of male tawny owl (Strix aluco) vocalizations in South Korea: call feature,individuality, and the potential use for census

Vocal individuality has been used as a monitoring tool, and two criteria are a prerequisite: high variation among individuals and low variation within individuals, and vocal consistency within and across seasons. We examined individual variation in the territorial hoot calls of the tawny owl (Strix aluco) to discriminate between males and to assess a possible conservation technique that would allow for monitoring individuals within a study area. The territorial calls were recorded from five males in the Naejang Mountain National Park in South Korea during the breeding season in 2015 and 2016 and analyzed both quantitatively and qualitatively to determine the amount of variation within and between individuals. Our results showed that the territorial calls were specific to individuals within a population and that the acoustic distances between males living in the same territory during the two years were the smallest for the four nesting sites. Our results suggest that territorial calls of the tawny owls are individually identifiable over two years and that this acoustic technique can be useful for monitoring individual site fidelity.     

Potential resource competition between an invasive mammal and native birds: overlap in tree cavity preferences of feral raccoons and Ural owls

Invasive mammals include good tree climbers that use tree cavities for resting and nesting. Tree cavities are important but limited resources in most forests; thus, some invasive mammals can be serious competitors for native cavity-using species, especially cavity-nesting birds. Despite the potential impact, such inter-class competition has rarely been considered. We examined the possibility of resource competition for tree cavities between the invasive raccoon Procyon lotor and the native Ural owl Strix uralensis. Both species are nocturnal and use tree cavities during daytime. We assessed an overlap in cavity use for both species as an indication of potential competition by monitoring 341 cavities during their breeding season in a natural park in Hokkaido, Japan. Of 341 potentially available cavities, raccoons and Ural owls used 37 and 32, respectively. The characteristics of 58 cavities used by raccoons or owls were compared to 49 random cavities to determine if they selected cavities with certain characteristics. As predicted from a large amount of tree cavities and a low raccoon density in this managed forest, we did not find direct evidence of competition, such as physical interaction, intrusion to cavities, or habitat segregation. Cavity types used by both species overlapped considerably in terms of height, entrance size, depth, and other characteristics: their habitats were widely overlapped. Further, in four cavities, one species was replaced by the other. Given the similar habitat requirements, the invasive raccoon could be a potential competitor for Ural owl when raccoon density increases and/or cavity availability decreases, which is the case for many forests in Japan. This study suggests that potential threats of resource competition among not only closely but also distantly related taxa should be taken into consideration when studying the impacts of invasive species.     

杯萼海桑和格氏海桑自然杂交的分子证据

Interspecific hybridization has been frequently observed in the mangrove genus Sonneratia. However, no natural hybridization has been reported between Sonneratia alba and S. griffithii to date, despite their overlapping distribution in the coast of Andaman Sea. In this study, cysteine proteinase inhibitor gene (cpi) from the nuclear genome, and two intergenic spacers (trnL-trnF and trnV-trnM) from the chloroplast genome, were sequenced to determine whether natural hybridization took place between the two species. Our results revealed two distinct types of cpi sequences from the putative hybrid matching those acquired from S. griffithii and S. alba, respectively. Sequencing of the chloroplast trnL-trnF and trnV-trnM regions showed that S. alba differed from S. griffithii by one nucleotide in each region, and the putative hybrid had the identical sequences with S. griffithii. Molecular data demonstrated clearly that there indeed existed natural hybridization between S. alba and S. griffithii, and that S. griffithii was the maternal parent in this hybridization event.     

Comparing alpha-diversity between plants and birds in a remnant wetland: evidence for a threshold and implication for management

In a Mediterranean patchy wetland of central Italy, we analyzed the relationship between the number of bird species, expressed in terms of bird alpha diversity, and plant alpha diversity, expressed as Hill number. This number (the exponential of the Shannon entropy) is considered one of the most strong and reliable indexes of alpha-diversity, synthesizing the information on evenness, richness and diversity in one single metric. We observed a progressive increase of the mean values of bird alpha diversity when plant alpha diversity increases along Hill number. Bird alpha diversity shows an abrupt increase between the first and the second of four categories of plant alpha diversity (0–1, >1–2, >2–3, >3), indicating a threshold response in all the groups considered (breeding, wintering and total bird assemblages). This marked decline of bird species richness at around 1 in the Hill index should represent an alarm for managers: wetland sites at or below this level of plant alpha diversity are likely to be experiencing a drastic decrease in bird species richness, both in spring (breeding birds) and in winter (wintering birds).     

SPA1: a gene important for chromosome segregation and other mitotic functions in S. cerevisiae

Human autoantibodies that recognize the spindle poles of mammals, plants, and insects were found to recognize two antigens in yeast. One of these proteins, called SPA1 (for Spindle Pole Antigen), is antigenically related to the spindle poles of a diverse set of organisms. The gene encoding SPA1 was cloned by immunoscreening a lambda gt11 yeast genomic DNA expression library with autoantibody probes. Mutational analysis of the SPA1 gene demonstrates that it is important for cell growth, chromosome segregation, and other cellular processes; spa1 mutants are viable but grow poorly at 30 degrees C, missegregate chromosomes at an increased frequency, and often contain deformed spindles. A significant fraction of spa1 mutant cells contain two or more nuclei, and others contain none; these abnormal cells may arise through a nuclear migration defect. Thus SPA1 represents a new fidelity gene that is important for chromosome segregation and other mitotic functions.     

MLPA-based evidence for sequence gain: pitfalls in confirmation and necessity for exclusion of false positives

Multiplex ligation-dependent probe amplification (MLPA) has become a standard method for identifying copy number mutations in diagnostic and research settings. The occurrence of false-positive deletion findings and the underlying causes are well recognized, whereas false-positive duplication/amplification findings have not been appreciated so far. We here present three pertinent cases which were only identified on extended, nonstandard secondary analyses. We also offer and experimentally validate a potential explanation. Our findings imply that MLPA data indicating gain of genomic sequence require validation on an independent sample or by an independent method.     

Mass changes in migrating birds: the evidence for fat and protein storage re-examined

The fact that one cannot kill a bird twice makes it very difficult to determine the relative contributions of fat and non-fat components to increases in body mass before migratory flights in individual birds. Knowing the relative contributions of these components is of obvious energetic interest since fat yields about eight times as much energy as fat-free muscle tissue. Several recent studies have failed to demonstrate convincingly, due to flaws in their analyses, that fat-free mass in addition to fat is accumulated before long-distance flights. We point out that regressions of fat or the non-fat component on total body mass cannot yield reliable estimates of the composition of individual mass changes in view of inter-individual variation in structural size, reserve levels or timing of storage. We suggest that studies over time of synchronous populations or marked individuals will give better answers. A re-analysis of published data indicates the widespread existence of fat-free tissue deposition during migration, whereas in some species fat alone explained the increase in total body mass. Larger species tend to incorporate a relatively higher proportion of non-fat components when increasing in mass. However, the comparative data set is not yet of sufficient quality to allow general statements on why, and to what extent in different individuals and species, non-fat tissue in addition to fat is deposited before take-off on migratory flights.     

Family study and segregation analysis of Tourette syndrome: evidence for a mixed model of inheritance.

To investigate the transmission of Tourette syndrome (TS) and associated disorders within families, complex segregation analysis was performed on family study data obtained from 53 independently ascertained children and adolescents with TS and their 154 first-degree relatives. The results suggest that the susceptibility for TS is conveyed by a major locus in combination with a multifactorial background. Other models of inheritance were definitively rejected, including strictly polygenic models, all single major locus models, and mixed models with dominant and recessive major loci. The frequency of the TS susceptibility allele was estimated to be .01. The major locus accounts for over half of the phenotypic variance for TS, whereas the multifactorial background accounts for approximately 40% of phenotypic variance. Penetrance estimates suggest that all individuals homozygous for the susceptibility allele at the major locus are affected, whereas only 2.2% of males and 0.3% of females heterozygous at the major locus are affected. Of individuals affected with TS, approximately 62% are heterozygous and approximately 38% are homozygous at the major locus. While none of the families had two parents affected with TS, 19% of families had two parents affected with the broader, phenotype, which includes TS, chronic tic disorder, or obsessive-compulsive disorder.     

Specializations in the lumbosacral spinal cord of birds: morphological and behavioural evidence for a sense of equilibrium.

Birds have a variety of long known anatomical specializations both in the vertebrae and in the spinal cord of lumbosacral segments. In the present investigation additional morphological specializations are described for the pigeon. These consist of segmentally organized semicircular canal-like structures (lumbosacral canals) which together with specializations in the meninges of the spinal cord form a large liquor space above accessory lobes attached to the spinal cord. The whole system is thought to function as a sense of equilibrium. The neurons in the lobes are assumed to be sensory neurons which are stimulated by the inertia of the fluid during movements of the body. Such a function is supported by lesion experiments: opening of the fluid space was followed by severe disturbances of landing and walking behavior.     

Chemical repellency in birds: relationship between chemical structure and avoidance response.

We examined how molecular structure of 24 anthranilate and benzoic acid derivatives correlated with drinking behavior in European starlings Sturnus vulgaris. The effectiveness of bird repellents was associated with basicity, the presence of an electron-donating group in resonance with an electron-withdrawing carboxylic group on a phenyl ring, and a heterocyclic ring in the same pi cloud plane as the phenyl ring. Of the benzoic acid derivatives tested in this study, methyl, ethyl, dimethyl, and linalyl anthranilate as well as anthranilic acid and 4-ketobenztriazine were repellent to birds. Water consumption was significantly reduced relative to control levels at concentrations as low as 0.05% (weight/volume) for the best repellents. Further statistical tests showed that reduction in consumption for the best repellents was absolute, not significantly different from zero consumption. Anthranilic acid isomers were moderately good repellents. The ability to generate a model predicting repellency allows for the efficient identification and development of ecologically sound, nonlethal, taxa-specific repellents to be used for the protection of wildlife in agricultural and industrial applications.     

Interaction dynamics between saprobic lignicolous fungi and Armillaria in controlled environments: Exploring the potential for competitive exclusion of Armillaria on peach

Armillaria root rot, caused by Armillaria tabescens and Armillaria mellea, is a major cause of premature tree death in peach orchards in the southeastern United States. The root systems of infected trees can become entirely colonized by Armillaria, serving as an inoculum source for adjacent trees and providing massive inoculum levels in replant situations. If dead or dying trees could be colonized by an effective competitor of Armillaria before their removal, the extent of root colonization by the pathogen could be reduced, thus decreasing the threat to adjacent trees and/or subsequent plantings. Interactions between five species of saprobic lignicolous fungi (Ganoderma lucidum, Hypholoma fasciculare, Phanerochaete velutina, Schizophyllum commune, and Xylaria hypoxylon) and the two Armillaria species were examined in controlled conditions to provide proof of concept for competitive exclusion of Armillaria from peach roots. On agar-coated glass slides, all five potential antagonists induced detrimental reactions in >58% of the Armillaria hyphae observed, with the majority resulting in hyphal swelling or granulation. On poplar wood blocks, all antagonists consistently either overgrew Armillaria colonies or—in the case of S. commune—engaged in deadlock reactions; in all cases, the viability of Armillaria colonies was reduced to <30% of that of unchallenged controls. When inoculated simultaneously onto opposite ends of peach root segments, all antagonists consistently reduced growth and viability of Armillaria on and under the bark, whereby reduction of pathogen growth underneath the bark, Armillaria’s primary ecological niche, was most pronounced for G. lucidum, S. commune, and X. hypoxylon. When root segments were allowed to be colonized entirely by Armillaria before being inoculated with the antagonists, the latter were able to overgrow the pathogen on the root surface but unable to pre-empt it from underneath the bark. In summary,G. lucidum, S. commune, and X. hypoxylon caused strong hyphal and mycelial interference reactions and the most pronounced reductions in growth of Armillaria above and below the bark, indicating that they would be the most promising candidates for field-scale evaluations to restrict colonization of dead or dying peach trees by Armillaria in the orchard.     

I-CeuI fragment analysis of the Shigella species: evidence for large-scale chromosome rearrangement in S. dysenteriae and S. flexneri

I-CeuI fragments of four Shigella species were analyzed to investigate their taxonomic distance from Escherichia coli and to collect substantiated evidence of their genetic relatedness because their ribosomal RNA sequences and similarity values of their chromosomal DNA/DNA hybridization had proved their taxonomic identity. I-CeuI digestion of genomic DNAs yielded seven fragments in every species, indicating that all the Shigella species contained seven sets of ribosome RNA operons. To determine the fragment identities, seven genes were selected from each I-CeuI fragment of E. coli strain K-12 and used as hybridization probes. Among the four Shigella species, S. boydii and S. sonnei showed hybridization patterns similar to those observed for E. coli strains; each gene probe hybridized to the I-CeuI fragments with sizes similar to that of the corresponding E. coli fragment. In contrast, S. dysenteriae and S. flexneri showed distinct patterns; rcsF and rbsR genes that located on different I-CeuI fragments in E. coli, fragments D and E, were found to co-locate on a fragment. Further analysis using an additional three genes that located on fragment D in K-12 revealed that some chromosome rearrangements involving the fragments corresponding to fragments D and E of K-12 took place in S. dysenteriae and S. flexneri.     

The gene for hypotrichosis of Marie Unna maps between D8S258 and D8S298: exclusion of the hr gene by cDNA and genomic sequencing.

Hypotrichosis of Marie Unna (MU) is an autosomal dominant hair-loss disorder with onset in childhood. A genomewide search for the gene was performed in a large Dutch family using 400 fluorescent microsatellite markers. Linkage was detected with marker D8S258, and analysis of this family and a further British kindred with additional markers in the region gave a combined maximum two-point LOD score of 13.42, with D8S560. Informative recombinants placed the MU gene in a 2.4-cM interval between markers D8S258 and D8S298. Recently, recessive mutations in the hr gene were reported in families with congenital atrichia, and this gene was previously mapped close to the MU interval. By radiation-hybrid mapping, we placed the hr gene close to D8S298 but were unable to exclude it from the MU interval. This, with the existence of the semidominant murine hr allele, prompted us to perform mutation analysis for this gene. Full-length sequencing of hr cDNA obtained from an affected individual showed no mutations. Similarly, screening of all exons of the hr gene amplified from the genomic DNA of an affected individual revealed no mutations. Analysis of expressed sequences and positional cloning of the MU locus is underway.     

Organization of telomere sequences in birds: evidence for arrays of extreme length and for in vivo shortening

Telomeres are the specialized ends of chromosomes consisting of highly conserved repeat (5'-TTAGGG-3')(n) sequences. Lack of information regarding the existence of an in vivo telomere clock function in birds, conflicting data regarding telomere array length in the chicken model, and the paucity of molecular telomere information for other avian species led us to study telomere array organization within and among 18 species and subspecies of birds. Most of the species contained between 2% and 4% telomere sequence per diploid genome. Arrays spanning 0.5-10 kb (Class I) and 10-40 kb (Class II) were observed in all of the species studied. Extremely long arrays, ranging from hundreds of kilobases to 1-2 Mb (Class III) were observed in all except two raptor species, the northern goshawk and American bald eagle. In chicken, there was evidence for shortening of the Class II arrays in vivo, based on intraindividual comparisons of somatic versus germline tissues in birds of different ages; terminally differentiated erythrocyte arrays were, on average, 2.3 kb shorter than sperm (germline) arrays. This study provides the first evidence for the existence of telomere arrays significantly larger than have been described for any vertebrate species to date and for developmentally programmed in vivo telomere shortening in the Aves taxa. The novel finding of megabase-sized telomere arrays may be an important feature of avian karyotypes that contain a large number of very small genetic units, the microchromosomes.     

Population genetics of Cryptosporidium meleagridis in humans and birds: evidence for cross-species transmission

Population genetic studies have been used to understand the transmission of pathogens in humans and animals, especially the role of zoonotic infections and evolution and dispersal of virulent subtypes. In this study, we analysed the genetic diversity and population structure of Cryptosporidium meleagridis, the only known Cryptosporidium species that infects both avian and mammalian hosts and is responsible for approximately 10% of human cryptosporidiosis in some areas. A total of 62 C. meleagridis specimens from children, AIDS patients, and birds in Lima, Peru were characterised by sequence analysis of the ssrRNA gene and five minisatellite, microsatellite and polymorphic markers in chromosome 6, including the 60 kDa glycoprotein (gp60), 47 kDa glycoprotein (CP47), a serine repeat antigen (MSC6-5), retinitis pigmentosa GTPase regulator (RPGR) and thrombospondin protein 8 (TSP8). The multilocus sequence analysis identified concurrent infections with Cryptosporidium hominis in four AIDS patients and three children. Unique subtypes of C. meleagridis ranged from eight at the gp60 locus (gene diversity –Hd = 0.651), three at the RPGR (Hd = 0.556), three at the MSC6-5 locus (Hd = 0.242), two at TSP8 (Hd = 0.198), to one at CP47 (monomorphic), much lower than that of C. hominis in the same area. Intragenic linkage disequilibrium was strong and complete at all gene loci. Intergenic linkage disequilibrium was highly significant (P < 0.001) for all pairs of polymorphic loci. Two major groups of subtypes were seen, with most subtypes belonging to group 1. Within group 1, there was no clear population segregation, and two of the 14 multilocus subtypes of C. meleagridis were found in both AIDS patients and birds. We believe that these results provide the first evidence of a clonal population structure of C. meleagridis and the likely occurrence of cross-species transmission of C. meleagridis between birds and humans.     

Discontinuous and incremental processes in the song learning of birds: evidence for a primer effect

Studies on the song learning in birds revealed a puzzling property of the acquisition system: Stimulus memorization becomes effective after remarkably few exposures, but nevertheless shows a relationship to the frequency of exposure to learning stimuli. This raises questions on the amount of learning that will occur during a given exposure to song. To examine this issue, we tutored handraised fledgling nightingales (Luscinia megarhynchos) with song strings, in which the serial succession of species-typical master songs was altered upon subsequent exposures. The sequencing of imitations obtained from the birds' adult singing revealed the following results: (1) A single exposure was sufficient for subjects to acquire serial information on song-type sequencing. (2) The first exposure to a master string played a key role for this accomplishment. (3) Nevertheless, the acquisition of serial information improved with increasing exposure frequency of master strings. (4) The acquisition of song patterns was not impaired by a non-regular presentation of master song-types. With respect to the particular salience of the first exposure for sequence memorization, we termed the phenomenon primer effect. The findings suggest that stimulus acquisition during perceptual song learning is mediated by a discontinuous process. Once acquired, information is then consolidated gradually, i.e. through an incremental process.     

Otoacoustic emissions in humans,birds, lizards,and frogs: evidence for multiple generation mechanisms

Many non-mammalian ears lack physiological features considered integral to the generation of otoacoustic emissions in mammals, including basilar-membrane traveling waves and hair-cell somatic motility. To help elucidate the mechanisms of emission generation, this study systematically measured and compared evoked emissions in all four classes of tetrapod vertebrates using identical stimulus paradigms. Overall emission levels are largest in the lizard and frog species studied and smallest in the chicken. Emission levels in humans, the only examined species with somatic hair cell motility, were intermediate. Both geckos and frogs exhibit substantially higher levels of high-order intermodulation distortion. Stimulus frequency emission phase-gradient delays are longest in humans but are at least 1 ms in all species. Comparisons between stimulus-frequency emission and distortion-product emission phase gradients for low stimulus levels indicate that representatives from all classes except frog show evidence for two distinct generation mechanisms analogous to the reflection- and distortion-source (i.e., place- and wave-fixed) mechanisms evident in mammals. Despite morphological differences, the results suggest the role of a scaling-symmetric traveling wave in chicken emission generation, similar to that in mammals, and perhaps some analog in the gecko.