- Proceedings. Biological sciences / The Royal Society
- Published about 7 years ago
The magnetic compass of a migratory bird, the European robin (Erithacus rubecula), was shown to be lateralized in favour of the right eye/left brain hemisphere. However, this seems to be a property of the avian magnetic compass that is not present from the beginning, but develops only as the birds grow older. During first migration in autumn, juvenile robins can orient by their magnetic compass with their right as well as with their left eye. In the following spring, however, the magnetic compass is already lateralized, but this lateralization is still flexible: it could be removed by covering the right eye for 6 h. During the following autumn migration, the lateralization becomes more strongly fixed, with a 6 h occlusion of the right eye no longer having an effect. This change from a bilateral to a lateralized magnetic compass appears to be a maturation process, the first such case known so far in birds. Because both eyes mediate identical information about the geomagnetic field, brain asymmetry for the magnetic compass could increase efficiency by setting the other hemisphere free for other processes.
A new computational model based on an optimal power, wake-only aerodynamics method is presented to predict the interdependency of energetics and kinematics in bird and bat flight. The model is divided into offline, intermediate and online modules. In the offline module, a four-dimensional design space sweep is performed (lift, thrust, flapping amplitude and flapping frequency). In the intermediate stage, the physical characteristics of the animal are introduced (wing span, mass, wing area, aspect ratio, etc.), and a series of amplitude-frequency response surfaces are constructed for all viable flight speeds. In the online component, the amplitude-frequency response surfaces are mined for the specific flapping motions being considered. The method is applied to several biological examples including a medium sized fruit bat (Cynopterus brachyotis), and two birds: a thrush nightingale (Luscinia luscinia) and a budgerigar (Melopsittacus undulatus). For each of these animals, the power and kinematics predictions are compared with available experimental data. These examples demonstrate that this new method can reasonably predict animal flight energetics and kinematics.
Differences in individual male birds' singing may serve as honest indicators of male quality in male-male competition and female mate choice. This has been shown e.g. for overall song output and repertoire size in many bird species. More recently, differences in structural song characteristics such as the performance of physically challenging song components were analysed in this regard. Here we show that buzz elements in the song of nightingales (Luscinia megarhynchos) hold the potential to serve as indicators of male quality and may therefore serve a communicative function. Buzzes were produced with considerable differences between males. The body weight of the males was correlated with one measure of these buzzes, namely the repetition rate of the buzz subunits, and individuals with larger repertoires sang buzzes at higher subunit-rates. A model of buzz performance constraints suggested that buzzes were sung with different proficiencies. In playback experiments, female nightingales showed more active behaviour when hearing buzz songs. The results support the idea that performance differences in the acoustic fine structure of song components are used in the communication of a large repertoire species such as the nightingale.
Music is thought to engage its listeners by driving feelings of surprise, tension, and relief through a dynamic mixture of predictable and unpredictable patterns, a property summarized here as “expressiveness”. Birdsong shares with music the goal to attract its listeners' attention and might use similar strategies to achieve this. We here tested a thrush nightingale’s (Luscinia luscinia) rhythm, as represented by song amplitude envelope (containing information on note timing, duration, and intensity), for evidence of expressiveness. We used multifractal analysis, which is designed to detect in a signal dynamic fluctuations between predictable and unpredictable states on multiple timescales (e.g. notes, subphrases, songs). Results show that rhythm is strongly multifractal, indicating fluctuations between predictable and unpredictable patterns. Moreover, comparing original songs with re-synthesized songs that lack all subtle deviations from the “standard” note envelopes, we find that deviations in note intensity and duration significantly contributed to multifractality. This suggests that birdsong is more dynamic due to subtle note timing patterns, often similar to musical operations like accelerando or crescendo. While different sources of these dynamics are conceivable, this study shows that multi-timescale rhythm fluctuations can be detected in birdsong, paving the path to studying mechanisms and function behind such patterns.
The use of network analysis to study complex animal communication systems: a study on nightingale song
- Proceedings. Biological sciences / The Royal Society
- Published over 5 years ago
The singing of song birds can form complex signal systems comprised of numerous subunits sung with distinct combinatorial properties that have been described as syntax-like. This complexity has inspired inquiries into similarities of bird song to human language; but the quantitative analysis and description of song sequences is a challenging task. In this study, we analysed song sequences of common nightingales (Luscinia megarhynchos) by means of a network analysis. We translated long nocturnal song sequences into networks of song types with song transitions as connectors. As network measures, we calculated shortest path length and transitivity and identified the ‘small-world’ character of nightingale song networks. Besides comparing network measures with conventional measures of song complexity, we also found a correlation between network measures and age of birds. Furthermore, we determined the numbers of in-coming and out-going edges of each song type, characterizing transition patterns. These transition patterns were shared across males for certain song types. Playbacks with different transition patterns provided first evidence that these patterns are responded to differently and thus play a role in singing interactions. We discuss potential functions of the network properties of song sequences in the framework of vocal leadership. Network approaches provide biologically meaningful parameters to describe the song structure of species with extremely large repertoires and complex rules of song retrieval.
Interspecific competition is assumed to play an important role in the ecological differentiation of species and speciation. However, empirical evidence for competition’s role in speciation remains surprisingly scarce. Here we studied the role of interspecific competition in the ecological differentiation and speciation of two closely related songbird species, the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (L. luscinia). Both species are insectivorous and ecologically very similar. They hybridize in a secondary contact zone, which is a mosaic of sites where both species co-occur (syntopy) and sites where only one species is present (allotopy). We analyzed fine-scale habitat data for both species in both syntopic and allotopic sites and looked for associations between habitat use and bill morphology, which have been previously shown to be more divergent in sympatry than in allopatry. We found that the two nightingale species differ in habitat use in allotopic sites, where L. megarhynchos occurred in drier habitats and at slightly higher elevations, but not in syntopic sites. Birds from allotopic sites also showed higher interspecific divergence in relative bill size compared to birds from syntopic sites. Finally, we found an association between bill morphology and elevation. Our results are consistent with the view that interspecific competition in nightingales has resulted in partial habitat segregation in sympatry, and that the habitat-specific food supply has in turn very likely led to bill size divergence. Such ecological divergence may enhance prezygotic as well as extrinsic postzygotic isolation and thus accelerate the completion of the speciation process. This article is protected by copyright. All rights reserved.
1.The role of interspecific competition for generating patterns in species' distribution is hotly debated and studies taking into account processes occurring at both large and small spatial scales are almost missing. Theoretically, competition between species with overlapping niches should result in divergence of their niches in sympatry to reduce the costs of competition. Many species show a mosaic distribution within sympatric zones, with the syntopic sites occupied by both species, and allotopic sites where only one species occurs. It is unclear whether such mosaics arise as a consequence of competition-driven niche segregation or due to the decline of their abundances towards range edges driven by environmental gradients. 2.If the interspecific competition matters, we should observe (i) a shift in habitat preferences of one or both species between syntopy and allotopy, and (ii) between allopatry and allotopy. Moreover, (iii) species should show greater divergence in their habitat preferences in allotopy than in allopatry where (iv) no differences in habitat preferences may occur. Finally, (v) shifts should be generally greater in the competitively subordinate species than in the dominant species. 3.We used a unique dataset on abundance of two closely related passerine species, the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (Luscinia luscinia), collected across their syntopy, allotopy and allopatry. The predictions were tested within a generalized mixed-effects modelling framework. 4.After accounting for environmental gradients perpendicular to the species' contact zone, we found a strong support for all but one prediction. Habitat preferences of both species shifted markedly between syntopy and allotopy, as well as between allopatry and allotopy. Whereas the species preferred the same habitats in allopatry, their preferences became strikingly different in allotopy where the abundance of the Common Nightingale increased towards dry and warm sites with low coverage of pastures, while the abundance of the Thrush Nightingale showed exactly opposite trends. Fifth prediction was not supported. 5.Our results indicate that the competition between closely related species can result in considerable changes in habitat use across their geographic ranges accompanied with divergence in their habitat preferences in sympatry. Here the species “escape” from competition to allotopic sites covered by habitats avoided by the competitor. Therefore, we argue that the interspecific competition is an important driver of species' distribution at both large and small spatial scales. This article is protected by copyright. All rights reserved.
Species of Plasmodium (Plasmodiidae, Haemosporida) are widespread and cause malaria, which can be severe in avian hosts. Molecular markers are essential to detect and identify parasites, but still absent for many avian malaria and related haemosporidian species. Here, we provide first molecular characterization of Plasmodium matutinum, a common agent of avian malaria. This parasite was isolated from a naturally infected thrush nightingale Luscinia luscinia (Muscicapidae). Fragments of mitochondrial, apicoplast and nuclear genomes were obtained. Domestic canaries Serinus canaria were susceptible after inoculation of infected blood, and the long-lasting light parasitemia developed in two exposed birds. Clinical signs of illness were not reported. Illustrations of blood stages of P. matutinum (pLINN1) are given, and phylogenetic analysis identified the closely related avian Plasmodium species. The phylogeny based on partial cytochrome b (cyt b) sequences suggests that this parasite is most closely related to Plasmodium tejerai (cyt b lineage pSPMAG01), a common malaria parasite of American birds. Both these parasites belong to subgenus Haemamoeba, and their blood stages are similar morphologically, particularly due to marked vacuolization of the cytoplasm in growing erythrocytic meronts. Molecular data show that transmission of P. matutinum (pLINN1) occurs broadly in the Holarctic, and the parasite likely is of cosmopolitan distribution. Passeriform birds and Culex mosquitoes are common hosts. This study provides first molecular markers for detection of P. matutinum.
The Nurses of Steeple Street Douglas Donna The Nurses of Steeple Street 432pp £5.99 Penguin 9780099599593 0099599597 [Formula: see text]
- Nursing standard (Royal College of Nursing (Great Britain) : 1987)
- Published almost 3 years ago
This new novel from the author of the Nightingale series does not disappoint.
1.Many partially migratory species show phenotypically divergent populations in terms of migratory behaviour, with climate hypothesized to be a major driver of such variability through its differential effects on sedentary and migratory individuals. 2.Based on long-term (1947-2011) bird ringing data, we analysed phenotypic differentiation of migratory behaviour among populations of the European robin Erithacus rubecula across Europe. 3.We showed that clusters of populations sharing breeding and wintering ranges varied from partial (British Isles and Western Europe, NW cluster) to completely migratory (Scandinavia and North-Eastern Europe, NE cluster). 4.Distance migrated by birds of the NE (but not of the NW) cluster decreased through time because of a north-eastwards shift in the wintering grounds. Moreover, when winter temperatures in the breeding areas were cold, individuals from the NE cluster also migrated longer distances, while those of the NW cluster moved over shorter distances. 5.Climatic conditions may therefore affect migratory behaviour of robins, although large geographical variation in response to climate seems to exist. This article is protected by copyright. All rights reserved.