ADULT NEST ATTENDANCE AND DIET OF NESTLING RESPLENDENT QUETZALS (PHAROMACHRUS MOCINNO) IN THE TALAMANCA MOUNTAINS OF SOUTHERN COSTA RICA

Abstract ∙ Resplendent Quetzals (Pharomachrus mocinno) inhabit mid to high elevation forests from southern Mexico to Panama. Lipid rich fruits from the Lauraceae family have been found to account for a large proportion of adult diet across their annual life cycle. To better understand the relationship between quetzals and Lauraceae during the breeding season, we studied food deliveries to nestlings in the Talamanca Mountains at San Gerardo de Dota, Costa Rica in the Rio Savegre watershed. Our study had four primary objectives: 1) determine parental contribution of males and females feeding nestling quetzals, 2) determine type of food delivered to nestling quetzals, 3) determine if deliveries of fruit items were related to their abundance and/or nutritional content and 4) determine if Lauraceae fruits made up a large proportion of nestling diets based on the high preference quetzals have displayed for fruits from this plant family. Hourly delivery rates were similar for the male and female (1.24 ± 0.68 and 1.44 ± 0.84). During the first 6 days, the largest proportion of the diet was animal prey; primarily lizards and beetles. After day 6, fruit rapidly became the dominant food item delivered to nestlings until fledging. The dominant number of fruits delivered to nestling quetzals were fruits from the Lauraceae family and included Ocotea holdrigeiana, Necatandra cufodontisii, and Aiouea costaricensis. All three had some of the highest protein and lipid content of all fruits delivered to nestlings. O. holdrigeiana had the highest protein and lipid content of all fruits delivered, had the lowest relative abundance, and was delivered more frequently than all other fruits. Conservation strategies for this species should take into account not just increasing available habitat, but also increasing habitat quality by focusing on species composition to provide abundant food plants for the Resplendent Quetzal to forage.Resumen ∙ Atención al nido y dieta de pichones del Quetzal Resplandeciente (Pharomachrus mocinno) en las Montañas Talamanca del sur de Costa Rica El Quetzal Resplandeciente (Pharomachrus mocinno) habita bosques de media a alta elevación del sur de México a Panamá. Frutas ricas en lípidos de la familia Lauraceae han sido consideradas constituyentes importantes de su dieta a lo largo de su ciclo anual de vida. Para entender mejor la relación entre quetzales y Lauraceae durante la temporada de cría, estudiamos entregas alimenticias a pichones en las montañas Talamanca en San Gerardo de Dota, Costa Rica en la Cuenca del Rio Savegre. Nuestro estudio tuvo cuatro objetivos primarios: 1) determinar la contribución del macho y la hembra en la alimentación de crías de quetzal, 2) determinar el tipo de entregas alimenticias a crías de quetzal, 3) determinar si las entregas de artículos frutales fueron relacionadas a su abundancia y/o contenido nutricional, y 4) determinar si frutas de Lauraceae conformaron una gran proporción de la dieta de crías de quetzal basado en la alta preferencia que quetzales han demostrado por frutas de esta familia. La proporción de entregas por hora fue similar en machos y hembras (1.24 ± 0.68 y 1.44 ± 0.84). Durante los primeros 6 días, presa animales constituyeron la mayor proporción de la dieta, ante todo lagartijas y escarabajos. Después del día 6, frutos constituyeron rápidamente el artículo de dieta dominante entregado a crías hasta que estas dejaron el nido. La mayor cantidad de frutas entregadas a crías de quetzal perteneció a la familia Lauraceae incluyendo Ocotea holdrigeiana, Nectandra cufodontisii, y Aiouea costaricensis. Las tres tuvieron el más alto contenido lipídico y de proteína de todas las frutas entregadas a crías. Interesantemente, O. holdrigeiana tuvo el más alto contenido lípido y de proteína de todas las frutas entregadas, la más baja abundancia relativa en el ambiente circundante, y fue utilizada más frecuentemente que todas las otras frutas. Estrategias de conservación para esta especie deben tomar en cuenta no solo incrementar el hábitat disponible, pero también incrementar la calidad del hábitat enfocándose en la composición de las especies vegetales, para asegurarse de proveer frutos en abundancia para la alimentación del Quetzal Resplandeciente

Interannual variations in fire weather, fire extent, and synoptic-scale circulation patterns in northern California and Oregon

The Mediterranean climate region on the west coast of the United States is characterized by wet winters and dry summers, and by high fire activity. The importance of synoptic-scale circulation patterns (ENSO, PDO, PNA) on fire-climate interactions is evident in contemporary fire data sets and in pre-Euroamerican tree-ring-based fire records. We investigated how interannual variability in two fire weather indices, the Haines index (HI) and the Energy Release Component (ERC), in the Mediterranean region of southern Oregon and northern California is related to atmospheric circulation and fire extent. Years with high and low fire weather index values corresponded to years with a high and low annual area burned, respectively. HI combines atmospheric moisture with atmospheric instability and variation in HI was more strongly associated with interannual variation in wildfire extent than ERC, which is based on moisture alone. The association between fire extent and HI was also higher for fires in southern Oregon than in northern California. In terms of synoptic-scale circulation patterns, years of high fire risk (i.e., increased potential for erratic fire behavior, represented by HI and ERC) were associated with positive winter PNA and PDO conditions, characterized by enhanced regional mid-tropospheric ridging and low atmospheric moisture. The time lag we found between fire risk potential and prior winter circulation patterns could contribute to the development of long-lead fire-climate forecastin

Gamma Oscillations in a Nonlinear Regime: A Minimal Model Approach Using Heterogeneous Integrate-and-Fire Networks

Fast oscillations and in particular gamma-band oscillation (20-80 Hz) are commonly observed during brain function and are at the center of several neural processing theories. In many cases, mathematical analysis of fast oscillations in neural networks has been focused on the transition between irregular and oscillatory firing viewed as an instability of the asynchronous activity. But in fact, brain slice experiments as well as detailed simulations of biological neural networks have produced a large corpus of results concerning the properties of fully developed oscillations that are far from this transition point. We propose here a mathematical approach to deal with nonlinear oscillations in a network of heterogeneous or noisy integrate-and-fire neurons connected by strong inhibition. This approach involves limited mathematical complexity and gives a good sense of the oscillation mechanism, making it an interesting tool to understand fast rhythmic activity in simulated or biological neural networks. A surprising result of our approach is that under some conditions, a change of the strength of inhibition only weakly influences the period of the oscillation. This is in contrast to standard theoretical and experimental models of interneuron network gamma oscillations (ING), where frequency tightly depends on inhibition strength, but it is similar to observations made in some in vitro preparations in the hippocampus and the olfactory bulb and in some detailed network models. This result is explained by the phenomenon of suppression that is known to occur in strongly coupled oscillating inhibitory networks but had not yet been related to the behavior of oscillation frequency

Polar mesoscale cyclones in the northeast Atlantic: Comparing climatologies from ERA-40 and satellite imagery

Polar mesoscale cyclones over the subarctic are thought to be an important component of the coupled atmosphere–ocean climate system. However, the relatively small scale of these features presents some concern as to their representation in the meteorological reanalysis datasets that are commonly used to drive ocean models. Here polar mesocyclones are detected in the 40-Year European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis dataset (ERA-40) in mean sea level pressure and 500-hPa geopotential height, using an automated cyclone detection algorithm. The results are compared to polar mesocyclones detected in satellite imagery over the northeast Atlantic, for the period October 1993–September 1995. Similar trends in monthly cyclone numbers and a similar spatial distribution are found. However, there is a bias in the size of cyclones detected in the reanalysis. Up to 80% of cyclones larger than 500 km are detected in MSL pressure, but this hit rate decreases, approximately linearly, to ∼40% for 250-km-scale cyclones and to ∼20% for 100-km-scale cyclones. Consequently a substantial component of the associated air–sea fluxes may be missing from the reanalysis, presenting a serious shortcoming when using such reanalysis data for ocean modeling simulations. Eight maxima in cyclone density are apparent in the mean sea level pressure, clustered around synoptic observing stations in the northeast Atlantic. They are likely spurious, and a result of unidentified shortcomings in the ERA-40 data assimilation procedure

Inferring connection proximity in networks of electrically coupled cells by subthreshold frequency response analysis

Electrical synapses continuously transfer signals bi-directionally from one cell to another, directly or indirectly via intermediate cells. Electrical synapses are common in many brain structures such as the inferior olive, the subcoeruleus nucleus and the neocortex, between neurons and between glial cells. In the cortex, interneurons have been shown to be electrically coupled and proposed to participate in large, continuous cortical syncytia, as opposed to smaller spatial domains of electrically coupled cells. However, to explore the significance of these findings it is imperative to map the electrical synaptic microcircuits, in analogy with in vitro studies on monosynaptic and disynaptic chemical coupling. Since "walking” from cell to cell over large distances with a glass pipette is challenging, microinjection of (fluorescent) dyes diffusing through gap-junctions remains so far the only method available to decipher such microcircuits even though technical limitations exist. Based on circuit theory, we derive analytical descriptions of the AC electrical coupling in networks of isopotential cells. We then suggest an operative electrophysiological protocol to distinguish between direct electrical connections and connections involving one or more intermediate cells. This method allows inferring the number of intermediate cells, generalizing the conventional coupling coefficient, which provides limited information. We validate our method through computer simulations, theoretical and numerical methods and electrophysiological paired recording

Fast Ray Features for Learning Irregular Shapes

We introduce a new class of image features, the Ray feature set, that consider image characteristics at distant contour points, capturing information which is difficult to represent with standard feature sets. This property allows Ray features to efficiently and robustly recognize deformable or irregular shapes, such as cells in microscopic imagery. Experiments show Ray features clearly outperform other powerful features including Haar-like features and Histograms of Oriented Gradients when applied to detecting irregularly shaped neuron nuclei and mitochondria. Ray features can also provide important complementary information to Haar features for other tasks such as face detection, reducing the number of weak learners and computational cost

Becoming a new neuron in the adult olfactory bulb

New neurons are continually recruited throughout adulthood in certain regions of the adult mammalian brain. How these cells mature and integrate into preexisting functional circuits remains unknown. Here we describe the physiological properties of newborn olfactory bulb interneurons at five different stages of their maturation in adult mice. Patch-clamp recordings were obtained from tangentially and radially migrating young neurons and from neurons in three subsequent maturation stages. Tangentially migrating neurons expressed extrasynaptic GABAA receptors and then AMPA receptors, before NMDA receptors appeared in radially migrating neurons. Spontaneous synaptic activity emerged soon after migration was complete, and spiking activity was the last characteristic to be acquired. This delayed excitability is unique to cells born in the adult and may protect circuits from uncontrolled neurotransmitter release and neural network disruption. Our results show that newly born cells recruited into the olfactory bulb become neurons, and a unique sequence of events leads to their functional integration

Disruption of Kcc2-dependent inhibition of olfactory bulb output neurons suggests its importance in odour discrimination

Synaptic inhibition in the olfactory bulb (OB), the first relay station of olfactory information, is believed to be important for odour discrimination. We interfered with GABAergic inhibition of mitral and tufted cells (M/T cells), the principal neurons of the OB, by disrupting their potassium- chloride cotransporter 2 (Kcc2). Roughly, 70% of mice died around 3 weeks, but surviving mice appeared normal. In these mice, the resulting increase in the intracellular Cl− concentration nearly abolished GABA-induced hyperpolarization of mitral cells (MCs) and unexpectedly increased the number of perisomatic synapses on MCs. In vivo analysis of odorant-induced OB electrical activity revealed increased M/T cell firing rate, altered phasing of action potentials in the breath cycle and disrupted separation of odour- induced M/T cell activity patterns. Mice also demonstrated a severely impaired ability to discriminate chemically similar odorants or odorant mixtures. Our work suggests that precisely tuned GABAergic inhibition onto M/T cells is crucial for M/T cell spike pattern separation needed to distinguish closely similar odours

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