Browsing by Autor "Oscar Laverde-R."

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Algorithms with low computational cost for monitoring and analysis of Colombia soundscapes
(2015) Luis Alfredo Quiroz; Luis Tobòn; Paula Caycedo; Oscar Laverde-R.
Studies focused on soundscape are important on biological conservation, because natural sounds are permanent and with dynamic properties, they have been linked to the welfare of the environment and the structure of the landscape. These studies usually analyze the sound in time and frequency domains, with computationally heavy and centralized algorithms. However, new technologies for real time analysis requires distributed algorithms with low computational cost. Hence, the present work evaluates the computational cost of alternative methods with potential applicability in analysis of time-varying signals. The analyzed methods are short time Fourier transform, harmonic expansion, wavelet transform (analytical and non-analytical Morlet, Mexican hat, and Paul) and orthogonal polynomial expansion (Legendre, Chebyshev, and Hermite). A comparison between these methods is presented, in which processing time, memory consumption, quality of reconstruction and grouping index are some of the features selected, resulting in a useful computational cost ranking. The methods are applied to several signals generated with different procedures, such as artificial modulated signals and natural recorded sounds (provided by The Alexander von Humboldt Institute). In conclusion, Harmonic expansion, Chebyshev expansion, Legendre expansion and Short Time Fourier Transform are the best methods with excellent performance in all features.
Bird diversity of the Cúcuta valley (Colombia) and biogeographical affinities with dry forest avifaunas of northern South America
(Wilson Ornithological Society, 2018) Jorge Enrique Avendaño; JuanPablo López-O.; Oscar Laverde-R.
Seasonally dry tropical forest is the least known and most threatened ecosystem in the Neotropics. In December 2009, we surveyed 3 tropical dry forest remnants in the arid Cúcuta valley, northeast Colombia. We recorded 140 of the 171 maximum species expected for the study area. Another 20 species were observed outside the inventory, totaling 160 species for the whole region. Results of the similarity analysis showed that the Cúcuta valley avifauna is biogeographically more related to the arid inter-Andean river valleys than to the Caribbean plains of Colombia and the Caribbean lowlands of northern Venezuela. This pattern of biogeographical affinities of dry forest bird communities in northwestern South America seems to be explained by the effect of geographic distance rather than environmental differences shaping species composition (β-diversity) and phylogenetic relatedness (phyloβ-diversity) across space. Our results highlight the uniqueness and need to protect the topical dry forest remnants of the Cúcuta valley.
Bird songs on the shelf: assessing vocal activity and output using data hidden in sound archives
(2017) Oscar Laverde-R.; Paula Caycedo‐Rosales; Paulo-C. Pulgarín-R.; Carlos Daniel Cadena
Abstract Understanding how often do animals emit communication signals is of critical importance to address a variety of research questions in behavioral ecology and sexual selection. However, information on vocal output, a central component of investment in signaling, is lacking for most species employing acoustic communication. Because this lack of information is partly due to logistical and methodological difficulties in monitoring animal signaling over time, developing new approaches to quantify vocal output is of special importance. We asked whether the number of recordings of avian vocalizations in sound archives and the times when such recordings were obtained reflect estimates of vocal output and temporal patterns of vocal activity obtained through systematic monitoring of wild bird populations in tropical forest sites. Based on a sample of 43 montane forest species, we found significant relationships between the number of recordings of species detected through continuous monitoring over several months and the number of recordings archived in sound collections, especially when accounting for the area of distribution of each species. In addition, daily activity patterns based on data collected through continuous monitoring over several days did not differ from those based on recordings archived in sound collections in 12 of 15 species of lowland forest birds. Annual patterns in vocal activity of two species estimated based on recordings in collections closely resembled previously published patterns. We conclude that recordings in sound collections contain valuable yet previously unappreciated information about the vocal output and temporal patterns in vocal activity of birds. This opens the possibility of using sound collections to assess vocal output and to consider it as a variable of interest in studies on the ecology and evolution of birds and other animals that use acoustic signals for communication. We encourage field workers to keep the ears wide open, and the recorders wide ready to record.
Estado, desarrollo y tendencias de los estudios en acústica de la fauna en Colombia
(Alexander von Humboldt Biological Resources Research Institute, 2021) Daniela Martínez-Medina; Orlando Acevedo‐Charry; Sofía Medellín-Becerra; Juliana Rodríguez-Fuentes; Silvia López‐Casas; Sebastián Muñoz-Duque; Mauricio Rivera‐Correa; Yelenny López-Aguirre; Fernando Vargas‐Salinas; Oscar Laverde-R.
Las señales acústicas son una de las formas de comunicación más importante en la fauna, incluso en la ubicación espacial de los individuos y sus presas. El estudio de las señales acústicas fortalece los campos de investigación en ecología, comportamiento, identificación taxonómica, uso de hábitat e incluso el efecto de las actividades humanas sobre diferentes especies animales. Además, es una herramienta para la cuantificación y monitoreo de la biodiversidad. En este trabajo presentamos un análisis de los estudios basados en bioacústica que se han desarrollado en Colombia, con el fin de establecer una línea base e identificar vacíos en el conocimiento, sus fortalezas y debilidades, para discutir los retos futuros para el desarrollo de la investigación sobre bioacústica en el país. Nuestra búsqueda de información se concentró en publicaciones de tipo científico, trabajos de grado y presentaciones en conferencias, a partir de plataformas de datos electrónicos, usando diferentes palabras claves. En total obtuvimos 321 trabajos, en los que los grupos taxonómicaos más estudiados fueron las aves (36.4%) y los anfibios (35%). La mayoría de los trabajos se concentran en la región Andina (63%). La bioacústica es un campo con un creciente interés y, por ende, resulta necesario el trabajo colaborativo y multidisciplinario, la consolidación en las metodologías y el fortalecimiento y enriquecimiento de las colecciones de sonidos del país.
New ecological information for the Black Tinamou (<i>Tinamus osgoodi hershkovitzi</i>)
(Oxford University Press, 2015) Pablo José Negret; Oscar Garzón; Pablo R. Stevenson; Oscar Laverde-R.
The Black Tinamou (Tinamus osgoodi) is a rare and endangered bird with two geographically disjunct subspecies. Very little pertinent information exists due to its secretive habits and cryptic coloration. Observations from a one-year study at Alto Fragua Indi Wasi National Park in southern Colombia have provided new ecological information for T. o. hershkovitzi. This subspecies vocalizes mostly between March and April, suggesting that the breeding season occurs during the first half of the year. Detections by camera traps indicate that this tinamou is more active in late morning, a pattern also found in other lowland tinamous. The subspecies was found in the entire study area, but more commonly at middle altitudes (1,400-1,600 m). We estimated a density of 13.47 birds km 2 , which is relatively high compared with the abundance of other tinamous of similar size. Despite the locally observed high density of this subspecies of Black Tinamou, high rates of logging and hunting in the area make this population vulnerable to rapid decline in the future.
Songs in the understory and colors in the canopy: habitat structure leads to different avian communication strategies in a tropical montane forest
(2018) Oscar Laverde-R.; Carlos Daniel Cadena
Abstract Birds inhabit a variety of habitats and they communicate using primarily visual and acoustic signals; two central hypotheses have been postulated to study the evolution of such a signals. The sensory drive hypothesis posits that variation in the physical properties of habitats leads to variation in natural selection pressures by affecting the ease with which different types of signals are perceived. Assuming that resources are limited for animals, the transfer hypothesis predicts a negative relationship between the investments in different types of signals. We evaluated these two hypotheses in a tropical montane forest bird assemblage. We also postulate a possible interaction between these two hypotheses: we predicted that the negative relationships between signals should be observed only when jointly considering birds from different environments (e.g. understory and canopy) due to the expected differences in communication strategies between habitats. The sensory drive hypothesis was supported by the differences we found between strata in vocal output, patch contrast to background and color conspicuousness, but not for the variables associated to song elaboration and hue disparity. We found support for the transfer hypothesis: birds with colors contrasting less against the background sing more frequently and birds with lower diversity of colors produce longer songs, understory birds showed also a negative relationship between signals, but only when accounting for phylogeny. We found partial support for the interaction between the sensory drive and the transfer hypotheses: hue disparity and vocal output were negatively related only when analyzing together birds from the canopy and the understory, but not when analyzing them separately. We conclude that the study of the evolution of communication signals needs to consider more than one channel and the functional interactions between them. The results of the interaction of optimal signaling strategies in two communication channels in the local habitats where animals signaling, are the patterns of colors and songs we revealed in a tropical montane forest bird assemblage.
The Andean Cock-of-the-rock ( <i>Rupicola peruvianus</i> ) is a frugivorous bird predator
(Wilson Ornithological Society, 2018) Laura Mahecha; Nickole Villabona; Laura Sierra; David Ocampo; Oscar Laverde-R.
Cotingas are considered essentially frugivorous, but a few records suggest they might include small vertebrates in their diet, mainly during the breeding season. In March 2015, we recorded a young male of an Andean Cock-of-the-rock (Rupicola peruvianus) chasing and eating an adult Canada Warbler (Cardellina canadensis) in Santa Maria, Boyacá (Colombia). The next day, we observed another adult male chasing a Swainson's Thrush (Catharus ustulatus), but we were unable to observe the end of the chase. Observations of hunting small vertebrates suggest this species may be omnivorous, not only during the breeding season but throughout its annual cycle. These may be rare cases, but notably both events involved migratory species that may not recognize these colorful birds as possible predators because they are not exposed to cotingas in the temperate zone. Predation on adult birds is difficult to observe in the wild, but this information is essential to better understand the life histories of birds and the different selection pressures acting on them.