The role of vocal consistency in bird communication, a case study in the blue tit (Cyanistes Caeruleus)

Birdsong is a multidimensional acoustic signal used for communication during intra- and intersexual interactions. The anatomical and behavioural adaptations related to sophisticated phonation skills indicate there are directional selection pressures shaping phonation mechanisms in songbirds. The level of neuro-motor challenge displayed while singing is normally referred to as vocal performance of song. Theoretical and empirical work has shown that vocal performance is related to individual quality and is meaningful during communication. Here, I use the blue tit (Cyanistes caeruleus) as a model species to investigate the communicative value of vocal performance in birdsong with particular emphasis on vocal consistency. Vocal consistency, as the ability to reproduce the same song element with minimal variation, has been proposed as an honest signal of individual quality in songbirds. In line with this hypothesis, I found that higher vocal consistency in males was preferred by females and was associated with increased reproductive success. I also provide evidence to validate the Spectral Cross-Correlation method used to measure vocal consistency, by showing it is sensitive to acoustic variation in natural birdsong. Although vocal consistency may be meaningful by itself, I built a multi-species database to investigate possible interactions of vocal consistency with other aspects of song. The results suggest there is a general trade-off between vocal performance within song and song length in birds. Following this finding, I conducted two playback experiments that showed that 1) long songs elicited a stronger response from territorial males than short songs but 2) that long songs with reduced vocal consistency triggered a lower response from territorial males, compared with short songs of high vocal consistency. These playback experiments indicated there is communicative value in the performance trade-off between song length and vocal consistency. Finally, I provide evidence that female song is frequent in blue tits and contextual behaviour data suggest it plays a role in intrasexual competition, similar to male song. However, during dawn chorus, males but not females were observed singing. These contextual differences indicate that female song may not be subjected to strong selection pressures related to seeking copulations. I hypothesize that such functional differences may relate to sexual differences in song parameters as females sang with lower song diversity and lower vocal performance than male

Astrobiochronology of Late Neogene deposits near the Strait of Gibraltar (SW Spain). Implications for the tectonic control of the Messinian Salinity Crisis

[EN]The main objective of this work is to explore the Guadalquivir basin and the Gulf of Cadiz to obtain continuous sediment records for the interval of the Messinian Salinity Crisis on the Atlantic side of the Iberian peninsula so as to analyse the possible paleoenvironmental, tectonic or paleoclimatic changes in a region which was only a few kms away from the Mediterranean coasts during this time period

Sea surface temperature reconstruction in the southeastern Iberian Margin during the Last Glacial period by means of coccolithophore analyses

4 pages, 2 figures.Detailed quantitative analyses of coccolithophore assemblages have been carried out in three sediment cores recovered from different locations in the Atlantic and Mediterranean sectors of the Iberian Peninsula. Biostratigraphical and oxygen isotope analyses show that these cores provide a high-resolution record of most of the last glacial period. Joint interpretation of the results reveals that higher sea surface temperatures (SST) were recorded in the Atlantic side during that interval. Dansgaard-Oeschger Interstadials are the warmer periods, while during Heinrich Events and Dansgaard-Oeschger Stadials SSTs suffered a substantial decrease, probably due to the appearance of turbid, fresher and colder surface water masses. These quantitative differences in the response of coccolithophore assemblages between the Atlantic and the Mediterranean cores indicate that the Mediterranean Sea shows a more intense response to climatic and oceanographic changes than the Atlantic area.La realización de esta investigación ha sido posible gracias a la concesión de una beca predoctoral del Programa Nacional de Formación de Profesorado Universitario (FPU, Ministerio de Educación, Cultura y Deportes) a E. Colmenero Hidalgo, y a la financiación de los proyectos REN2003-08642-CO2/CLI y BTE2002-04670 (Ministerio de Ciencia y Tecnología), SA088/04 (Junta de Castilla y León) y PROMESS 1 (EVR1-T-40024, Comisión Europea). Los autores también agradecen a Jesús Roncero y a José Ignacio Martín Cruz su ayuda en la preparación de muestras.Peer reviewe

Impact of suborbital climate changes in the North Atlantic on ice sheet dynamics at the Mid-Pleistocene Transition

Early and Mid-Pleistocene climate, ocean hydrography and ice sheet dynamics have been reconstructed using a high-resolution data set (planktonic and benthic delta O-18 time series, faunal-based sea surface temperature (SST) reconstructions and ice-rafted debris (IRD)) record from a high-deposition-rate sedimentary succession recovered at the Gardar Drift formation in the subpolar North Atlantic (Integrated Ocean Drilling Program Leg 306, Site U1314). Our sedimentary record spans from late in Marine Isotope Stage (MIS) 31 to MIS 19 (1069-779 ka). Different trends of the benthic and planktonic oxygen isotopes, SST and IRD records before and after MIS 25 (similar to 940 ka) evidence the large increase in Northern Hemisphere ice-volume, linked to the cyclicity change from the 41-kyr to the 100-kyr that occurred during the Mid-Pleistocene Transition (MPT). Beside longer glacial-interglacial (G-IG) variability, millennial-scale fluctuations were a pervasive feature across our study. Negative excursions in the benthic delta O-18 time series observed at the times of IRD events may be related to glacio-eustatic changes due to ice sheets retreats and/or to changes in deep hydrography. Time series analysis on surface water proxies (IRD, SST and planktonic delta O-18) of the interval between MIS 31 to MIS 26 shows that the timing of these millennial-scale climate changes are related to half-precessional (10 kyr) components of the insolation forcing, which are interpreted as cross-equatorial heat transport toward high latitudes during both equinox insolation maxima at the equator

The response of SST to insolation and ice sheet variability from MIS 3 to MIS 11 in the northwestern Mediterranean Sea (Gulf of Lions)

Here we present a sea surface temperature (SST) record based on the Uk′ 37 index from the PRGL1 borehole (Promess1) drilled on the upper slope of the Gulf of Lions (GL). This is the first continuous and high-resolution record in the northwestern Mediterranean Sea from marine oxygen isotope stage 3 (MIS) 3 to MIS 11. Due the location of the GL, the SST proxy can be considered to be a reliable tool to study the climate link between high latitude and midlatitude. During glacial inceptions, the northern ice sheet signal via cold northwesterly winds was first recorded in our study area in comparison with southern locations, highlighting the strong sensitivity of this location to high-latitude dynamics. Moreover, the amplitude of the millennial-scale variability in the western Mediterranean basin seems to be the result of both ice sheet and insolation variability. © 2015. American Geophysical Union. All Rights Reserved.Two anonymous reviewers are greatly acknowledged for their comments that improved the final version of this manuscript. This work was funded by GRACCIE project (CONSOLIDERINGENIO CSD 2007–00067) and by the Formación de Personal Investigador (FPI) grant BES-2007-17602. Supporting data available at http://doi.pangaea.de/10.1594/PANGAEA.854682Peer reviewe

Climate-driven changes in sedimentation rate influence phosphorus burial along continental margins of the northwestern Mediterranean

The burial of phosphorus (P) in continental margin sediments is a critical component of the marine reactive P budget, and thus an important factor in marine biological productivity. We determined downcore records of P from a site drilled on the upper slope of the Gulf of Lions (PRGL 1), northwestern Mediterranean Sea. Changes in total P content were monitored from Marine Isotope Stage (MIS) 6 to MIS 11. In addition, in two selected intervals (248–277 ka and 306–342 ka) the total P record was expanded by adding detailed geochemical analyses of the various P fractions, including oxyhydroxide-associated P, authigenic P, detrital P and organic P. Increased sedimentation rates during glacials owing to seaward migration of the Rhone's mouth, enhanced the burial of reactive P (oxyhydroxide-associated + authigenic + organic) phases by decreasing its time at the reactive sediment/water interface, in turn resulting in increasing proportion of authigenic to detrital phosphorus. The inverse was found for interglacial stages. The effects of glacial/interglacial variation in sedimentation rate over P geochemistry resulted in changes in sediment-water interface oxygenation, as well as in the efficiency of P burial, as shown by (C:P)org and Corg:Preact proxies respectively. Two events of high P deposition associated with authigenic P formation, at 335 ka (Paut1) and 275 ka (Paut2), were associated with periods of rapid disintegration of North Atlantic ice sheets leading to Ice Rafted Debris (IRD) deposition. These high P deposition events appear to be linked to short warm periods that followed cold episodes. Enhanced continental runoff owing to more humid conditions during short warm episodes could play a critical role for enhanced biogenic productivity and posterior authigenic P accumulation

Sexual selection for both diversity and repetition in birdsong

From fiddler crabs to humans, animals perform repetitive displays showing neuromotor skill and vigour. Consistent repetition of identical notes (vocal consistency) facilitates the assessment of neuromotor skills and is important in communication in birds. Most birdsong research has focused on song diversity as a signal of individual quality, which seems contradictory as repetition is extremely common in most species. Here we show that consistent repetition within songs is positively correlated with reproductive success in male blue tits (Cyanistes caeruleus). A playback experiment shows that females are sexually aroused by male songs with high levels of vocal consistency, which also peaks seasonally during the fertile period of the female, supporting the role of vocal consistency in mate choice. Male vocal consistency also increases with subsequent repetitions of the same song type (a warm-up effect) which conflicts with the fact that females habituate to repeated song, showing decreased arousal. Importantly, we find that switching song types elicits significant dishabituation within the playback, supporting the habituation hypothesis as an evolutionary mechanism driving song diversity in birds. An optimal balance between repetition and diversity may explain the singing style of many bird species and displays of other animals

Sound properties affect measurement of vocal consistency in birdsong: validation of the spectrogram cross correlation method (SPCC)

In songbirds, singing with precision (vocal consistency) has been proposed to reflect whole-organism performance. Vocal consistency is measured using spectrogram cross correlation (SPCC) to assess the acoustic similarity between subsequent renditions of the same note. To quantify how SPCC is sensitive to the acoustic discrepancies found in birdsong, we created a set of 40 000 synthetic sounds that were designed based on the songs of 345 species. This set included 10 000 reference sounds and 30 000 inexact variants with quantified differences in frequency, bandwidth, or duration with respect to the reference sounds. We found that SPCC is sensitive to acoustic discrepancies within the natural range of vocal consistency, supporting the use of this method as a tool to assess vocal consistency in songbirds. Importantly, the sensitivity of SPCC was significantly affected by the bandwidth of sounds. The predictions derived from the analysis of synthetic sounds were then validated using 954 song recordings from 345 species (20 families). Based on psychoacoustic studies from birds and humans, we propose that the sensitivity of SPCC to acoustic discrepancies mirrors a perceptual bias in sound discrimination. Nevertheless, we suggest the tool be used with care, since sound bandwidth varies considerably between singing styles and therefore, SPCC scores may not be comparable

A limit to sustained performance constrains trill length in birdsong

In birds, song performance determines the outcome of contests over crucial resources. We hypothesized that 1) sustained performance is limited within song, resulting in a performance decline towards the end and 2) the impact of song length is compromised if performance declines. To test these hypotheses, we analyzed the songs of 597 bird species (26 families) and conducted a playback experiment on blue tits (Cyanistes caeruleus). Our multi-species analysis showed that song performance declines after sustained singing, supporting our hypothesis. If the performance decline is determined by individual attributes (i.e., physical condition), our results explain how trill length can honestly signal quality. Our experiment showed that longer trills of high performance elicited a stronger response during territorial interactions. However, long trills that declined in performance elicited a weaker response than short, high-performance trills. A trade-off between the duration and performance quality of a motor display can be an important aspect in communication across taxa

Millennial surface water dynamics in the Ría de Vigo during the last 3000 years as revealed by coccoliths and molecular biomarkers

13 pages, 7 figures, 2 tables.-- Printed version published Mar 10, 2005.A combined study of coccolith assemblages and biomarkers in a gravity core collected from the Ría de Vigo (NW Spain) allowed us to reconstruct the paleoenvironmental conditions for the last 3000 years. The quantitative distribution of coccolithophore species points to three different intervals within the core, dated by AMS radiocarbon measurements. The first interval (ca. 975 BC–252 AD), characterized by high abundances of Calcidiscus leptoporus and Gephyrocapsa muellerae, is thought to represent moderate water temperatures, suggesting a transition from a warmer to a cooler period. The second interval (ca. 252–1368 AD), characterized by the dominance of Coccolithus pelagicus, Helicosphaera carteri and Syracosphaera spp., and a high concentration of hexacosanol linked to terrestrial input, is interpreted as having been a humid period with fluvial input. The third interval (ca. 1368 AD–1950) is characterized by a high abundance of Gephyrocapsa oceanica, high alkenone values and low values of hexacosanol, and is thought to represent a period dominated by oceanic conditions within the Ría.Taking into account the ocean–atmospheric system affecting the region studied, here we propose an alternation in the mean state of North Atlantic Oscillation (NAO) at millennial time scales. A well-developed upwelling system and an active Ría–ocean connection during the warmer interval I suggest a NAO+ phase influenced by a Hypsithermal period. The occurrence of the humid and relatively warm interval II is consistent with a negative phase in the NAO, as well as a relative restriction in ocean–Ría exchange. Interval III, which was drier and more productive, again suggests the dominance of a positive phase in the NAO, with a more intense oceanic connection and more energized upwelling.Research grants ABRUMIS REN2003-08642-C02-02/CLI, BTE2002-04670 (Ministerio de Ciencia y Tecnología) and SA088/04 (Junta de Castilla y León) supported this study.Peer reviewe