Avian predators taste reject mimetic prey in relation to their signal reliability

Aposematic organisms defend themselves through various means to increase their unprofitability to predators which they advertise with conspicuous warning signals. Predators learn to avoid aposematic prey through associative learning that leads to lower predation. However, when these visual signals become unreliable (e.g., through automimicry or Batesian mimicry), predators may switch from using visual signals to taste sampling prey to choose among them. In this experiment, we tested this possibility in a field experiment where we released a total of 4800 mealworm prey in two clusters consisting of either: (i) undefended prey (injected with water) and (ii) model-mimics (injected with either quinine sulphate [models] or water [mimics]). Prey were deployed at 12 sites, with the mimic frequency of the model-mimics ranging between 0 and 1 (at 0.2 intervals). We found that taste rejection peaked at moderate mimic frequencies (0.4 and 0.6), supporting the idea that taste sampling and rejection of prey is related to signal reliability and predator uncertainty. This is the first time that taste-rejection has been shown to be related to the reliability of prey signals in a mimetic prey system

The diet of Great Tit Parus major nestlings in a Mediterranean Iberian forest: the important role of spiders

Dieta de los pollos de Carbonero Común Parus major en un bosque Ibérico Mediterraneo: la importáncia de las arañas La dieta del Carbonero Común Parus major cuando alimenta a los pollos ha sido descrita en muchos artículos. Sin embargo, la información sobre el área mediterránea es bastante escasa. Aquí describimos la dieta de los pollos en una población de Carbonero Común en un bosque Mediterráneo de Barcelona (nordeste de España) en dos temporadas de cría a través de dos métodos (collares y grabaciones de video). Las principales presas cebadas fueron las orugas (44% a partir de datos de collares y 62% a partir de datos de grabaciones), pero en nuestras latitudes las arañas parecen ser un importante recurso (24% [datos collares] y 42% [datos de grabaciones]). No encontramos diferencias significativas en la cantidad de arañas recolectadas por los padres en relación con el estado de desarrollo de los pollos, vegetación alrededor de las cajas nido, tamaño de puesta y año. Nuestros resultados subrayan la importancia de las arañas como recurso trófico en ambientes mediterráneos. Palabras clave: Carbonero Común, Pollos, Dieta, Arañas.The diet of the Great Tit Parus major when rearing chicks has been described in many studies. However, data from the Mediterranean area is scarce. Here we describe the diet of nestlings in a population of Great Tits in a Mediterranean forest in Barcelona (north–east Spain) during two breeding seasons using two methods: neck–collars and video recording. The main prey were caterpillars (44% from neck–collar data and 62% from video–recorded data), but in our latitudes spiders also seemed to be an important food resource (24% from neck–collar data and 42% from video–recorded data). We did not find any significant differences in the quantity of spiders collected by parents in relation to stage of chick development, main vegetation surrounding nest boxes, size of the brood, or year. Our results stress the importance of spiders as a food source in Mediterranean habitats. Key words: Great Tits, Nestlings, Diet, Spiders.Dieta de los pollos de Carbonero Común Parus major en un bosque Ibérico Mediterraneo: la importáncia de las arañas La dieta del Carbonero Común Parus major cuando alimenta a los pollos ha sido descrita en muchos artículos. Sin embargo, la información sobre el área mediterránea es bastante escasa. Aquí describimos la dieta de los pollos en una población de Carbonero Común en un bosque Mediterráneo de Barcelona (nordeste de España) en dos temporadas de cría a través de dos métodos (collares y grabaciones de video). Las principales presas cebadas fueron las orugas (44% a partir de datos de collares y 62% a partir de datos de grabaciones), pero en nuestras latitudes las arañas parecen ser un importante recurso (24% [datos collares] y 42% [datos de grabaciones]). No encontramos diferencias significativas en la cantidad de arañas recolectadas por los padres en relación con el estado de desarrollo de los pollos, vegetación alrededor de las cajas nido, tamaño de puesta y año. Nuestros resultados subrayan la importancia de las arañas como recurso trófico en ambientes mediterráneos. Palabras clave: Carbonero Común, Pollos, Dieta, Arañas

Comparing prey composition and prey size delivered to nestlings by great tits, Parus major, and blue tits, Cyanistes caeruleus, in a Mediterranean sclerophyllous mixed forest

Resource partitioning is a central issue in ecology because it can establish to which point similar species can coexist in the same habitat. Great tits and blue tits have been classical model species in studies of trophic competence. However, most studies on the topic have been conducted at localities where caterpillars are by far the most relevant prey brought to the nestlings. In Mediterranean mixed forests, nevertheless, the abundance of caterpillars is relatively low and it is spiders that play a key role in the diet of great tits, at least for nestlings. The aim of this paper was to study nest food provisioning to establish the degree of diet overlap of these two tit species in a Mediterranean forest. Our results showed that blue tit feeding rates were higher than those of great tits, probably to compensate for the smaller prey delivered to nestlings by blue tits. Blue tits brought more spiders than great tits, while grey tits brought larger prey and more caterpillars. This may be because larger great tits can prey upon larger prey items than blue tits. As a main result, this study supports the view of resource partitioning by great and blue tits in sclerophyllous Mediterranean forest ecosystem

Isotopic niche overlap between the invasive leiothrix and potential native competitors

We analysed niche overlap between the red–billed leiothrix Leiothrix lutea, a spreading exotic invasive bird, and the European robin Erithacus rubecula and the blackcap Sylvia atricapilla, similar native species, which are commonly considered as potential competitors in Mediterranean forests. We analyzed stable isotope ratios (δ13C and δ15N) from feathers of birds sampled in several locations within the Collserola mountain range (Barcelona, NE Spain) where leiothrix have strongly increased their numbers in the last decade and quantified niche overlap with nicheROVER. Blackcap individuals showed the lowest probability to be found in the isotopic niche of the other two species (around 60 %), while leiothrix and robins showed a high probability to share the same isotopic niche (82 %). Our results stress that competition for resources is potentially high and the species shared marked niche asymmetries, which may have implications for community dynamics in the long term

Prey choice, provisioning behaviour, and effects of early nutrition on nestling phenotype of titmice

[EN] It is generally assumed that blue and great tits (Cyanistes caeruleus, Parus major) compete for the same type of food (Lepidoptera larvae) during the breeding season and that the former have some advantage because they are usually earlier and can exploit small caterpillars that are often more abundant and are not consumed by great tits. However, it is not clear whether, when confronted with similar circumstances (e.g., nestling demand), blue and great tits show similar preferences for a particular caterpillar type. In this 2-y study, we compare the diet of both tit species in detail by controlling for hatching date and brood size. We also examine how the contribution of caterpillars and spiders to the diet is related to nestling development. A positive relationship was found between the percentage of spiders in the diet and nestling tarsus length in both species, reinforcing the idea that neonatal nutrition could have a strong influence on nestling phenotype (e.g., offspring size). Such a correlation may arise because spiders contain a high level of taurine, an essential nutrient in the early development of young, and/or this prey type contains more calcium than other food items, which may affect the rate of nestling bone mineralization. Blue tits fed their young double the number of tortricid larvae in comparison with great tits, whereas the latter showed a clear preference for noctuids and exploited, with a low frequency, a type of larvae not consumed by blue tits, hairy caterpillars (Lasiocampidae). Our results point to resource partitioning by these species in this forest ecosystem and contribute to a better understanding of feeding ecology of titmice, which is particularly timely in a global warming context [FR] Il est généralement admis que les mésanges bleues (Cyanistes caeruleus) et les mésanges charbonnières (Parus major) se font compétition pour le même type de nourriture (larves de lépidoptères) durant la période de reproduction. Il est également admis que les mésanges bleues possèdent un certain avantage, car elles se reproduisent plus tôt et mangent de petites chenilles souvent plus abondantes qui ne sont pas consommées par les mésanges charbonnières. Cependant, il n'est pas clair si dans les mêmes conditions (ex. de demande en nourriture des oisillons), les mésanges bleues et charbonnières préfèrent les mêmes types de chenilles. Dans cette étude de 2 ans, nous avons comparé en détail les régimes alimentaires des 2 espèces de mésanges en contrôlant pour la date de ponte et la taille de la couvée. Nous avons aussi examiné si les contributions des chenilles et des araignées au régime alimentaire étaient reliées au développement des oisillons. Chez les 2 espèces, une relation positive a été trouvée entre le pourcentage d'araignées dans le régime alimentaire et la longueur du tarse des oisillons renforçant ainsi l'idée que la nutrition néonatale peut avoir une grande influence sur le phénotype des oisillons (ex. la taille des jeunes). Une telle corrélation peut résulter du fait que les araignées ont un taux élevé de taurine, un nutriment essentiel au développement précoce des jeunes, et/ou que ce type de proie contient plus de calcium que d'autres aliments ce qui peut influencer le taux de minéralisation des os chez les oisillons. Les mésanges bleues ont nourri leurs jeunes avec deux fois plus de larves de tortricidés que les mésanges charbonnières qui elles ont montré une nette préférence pour les noctuidés. Ces dernières ont aussi consommé, quoique peu fréquemment, des livrées (Lasiocampidae), un type de larves boudé par les mésanges bleues. Nos résultats pointent vers une division des ressources entre ces espèces dans cet écosystème forestier et contribuent à une meilleure compréhension de l'écologie alimentaire des mésanges ce qui est particulièrement utile dans un contexte de réchauffement climatiqueV. García-Navas was supported by a FPI predoctoral fellowship (Spanish Ministry of Science and Innovation (MICINN)-European Social Fund). This study was financed by the MICINN (grant reference: GCL2007-61395)Peer Reviewe

<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties

Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues – a realisation of the Tycho-Gaia Astrometric Solution (TGAS) – and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. For the subset of ∼94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr−1. For the secondary astrometric data set, the typical uncertainty of the positions is ∼10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼0.03 mag over the magnitude range 5 to 20.7. Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data

Gaia data release 1, the photometric data

CONTEXT. This paper presents an overview of the photometric data that are part of the first Gaia data release. AIMS. The principles of the processing and the main characteristics of the Gaia photometric data are presented. METHODS. The calibration strategy is outlined briefly and the main properties of the resulting photometry are presented. RESULTS. Relations with other broadband photometric systems are provided. The overall precision for the Gaia photometry is shown to be at the milli-magnitude level and has a clear potential to improve further in future releases

Gaia Early Data Release 3: Summary of the contents and survey properties

ABSTRACT: Context. We present the early installment of the third Gaia data release, Gaia EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the list of radial velocities from Gaia DR2. Aims. A summary of the contents of Gaia EDR3 is presented, accompanied by a discussion on the differences with respect to Gaia DR2 and an overview of the main limitations which are present in the survey. Recommendations are made on the responsible use of Gaia EDR3 results. Methods. The raw data collected with the Gaia instruments during the first 34 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium and turned into this early third data release, which represents a major advance with respect to Gaia DR2 in terms of astrometric and photometric precision, accuracy, and homogeneity. Results. Gaia EDR3 contains celestial positions and the apparent brightness in G for approximately 1.8 billion sources. For 1.5 billion of those sources, parallaxes, proper motions, and the (GBP ? GRP) colour are also available. The passbands for G, GBP, and GRP are provided as part of the release. For ease of use, the 7 million radial velocities from Gaia DR2 are included in this release, after the removal of a small number of spurious values. New radial velocities will appear as part of Gaia DR3. Finally, Gaia EDR3 represents an updated materialisation of the celestial reference frame (CRF) in the optical, the Gaia-CRF3, which is based solely on extragalactic sources. The creation of the source list for Gaia EDR3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. The source list is largely the same as that for Gaia DR2, but it does feature new sources and there are some notable changes. The source list will not change for Gaia DR3. Conclusions. Gaia EDR3 represents a significant advance over Gaia DR2, with parallax precisions increased by 30 per cent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30-40% for the parallaxes and by a factor ~2.5 for the proper motions. The photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. A single passband for G, GBP, and GRP is valid over the entire magnitude and colour range, with no systematics above the 1% levelThe Gaia mission and data processing have financially been supported by ; the Spanish Ministry of Economy (MINECO/FEDER, UE) through grants ESP2016-80079-C2-1-R, ESP2016-80079-C2-2-R, RTI2018-095076-B-C21, RTI2018-095076-B-C22, BES-2016-078499, and BES-2017-083126 and the Juan de la Cierva formación 2015 grant FJCI-2015-2671, the Spanish Ministry of Education, Culture, and Sports through grant FPU16/03827, the Spanish Ministry of Science and Innovation (MICINN) through grant AYA2017-89841P for project “Estudio de las propiedades de los fósiles estelares en el entorno del Grupo Local” and through grant TIN2015-65316-P for project “Computación de Altas Prestaciones VII

Gaia Focused Product Release: Radial velocity time series of long-period variables

The third Gaia Data Release (DR3) provided photometric time series of more than 2 million long-period variable (LPV) candidates. Anticipating the publication of full radial-velocity (RV) in DR4, this Focused Product Release (FPR) provides RV time series for a selection of LPVs with high-quality observations. We describe the production and content of the Gaia catalog of LPV RV time series, and the methods used to compute variability parameters published in the Gaia FPR. Starting from the DR3 LPVs catalog, we applied filters to construct a sample of sources with high-quality RV measurements. We modeled their RV and photometric time series to derive their periods and amplitudes, and further refined the sample by requiring compatibility between the RV period and at least one of the $G$, $G_{\rm BP}$, or $G_{\rm RP}$ photometric periods. The catalog includes RV time series and variability parameters for 9\,614 sources in the magnitude range $6\lesssim G/{\rm mag}\lesssim 14$, including a flagged top-quality subsample of 6\,093 stars whose RV periods are fully compatible with the values derived from the $G$, $G_{\rm BP}$, and $G_{\rm RP}$ photometric time series. The RV time series contain a mean of 24 measurements per source taken unevenly over a duration of about three years. We identify the great most sources (88%) as genuine LPVs, with about half of them showing a pulsation period and the other half displaying a long secondary period. The remaining 12% consists of candidate ellipsoidal binaries. Quality checks against RVs available in the literature show excellent agreement. We provide illustrative examples and cautionary remarks. The publication of RV time series for almost 10\,000 LPVs constitutes, by far, the largest such database available to date in the literature. The availability of simultaneous photometric measurements gives a unique added value to the Gaia catalog (abridged)Comment: 36 pages, 38 figure