Showing papers by "Willem Bouten published in 2012"
TL;DR: RNCEP as discussed by the authors is a package of functions in the open-source R language to access, organize and visualise freely available atmospheric data from two long-term high-quality data sets with global coverage.
Abstract: Atmospheric conditions strongly influence ecological systems, and tools that simplify the access and processing of atmospheric data can greatly facilitate ecological research. We have developed RNCEP, a package of functions in the open-source R language, to access, organise and visualise freely available atmospheric data from two long-term high-quality data sets with global coverage. These functions retrieve data, via the Internet, for either a desired spatiotemporal extent or interpolated to a point in space and time. The package also contains functions to temporally aggregate data, producing user-defined variables, and to visualise these data on a map. By making access to atmospheric data and integration with biological data easier and more flexible, we hope to facilitate and encourage the exploration of relationships between biological systems and atmospheric conditions.
186 citations
TL;DR: The workflow design presented in this study can facilitate model development, be adapted to a wide range of species, and together with the appropriate measurements, can foster the study of behaviour and habitat use of free living animals throughout their annual routine.
Abstract: Animal-borne sensors enable researchers to remotely track animals, their physiological state and body movements. Accelerometers, for example, have been used in several studies to measure body movement, posture, and energy expenditure, although predominantly in marine animals. In many studies, behaviour is often inferred from expert interpretation of sensor data and not validated with direct observations of the animal. The aim of this study was to derive models that could be used to classify oystercatcher (Haematopus ostralegus) behaviour based on sensor data. We measured the location, speed, and tri-axial acceleration of three oystercatchers using a flexible GPS tracking system and conducted simultaneous visual observations of the behaviour of these birds in their natural environment. We then used these data to develop three supervised classification trees of behaviour and finally applied one of the models to calculate time-activity budgets. The model based on accelerometer data developed to classify three behaviours (fly, terrestrial locomotion, and no movement) was much more accurate (cross-validation error = 0.14) than the model based on GPS-speed alone (cross-validation error = 0.35). The most parsimonious acceleration model designed to classify eight behaviours could distinguish five: fly, forage, body care, stand, and sit (cross-validation error = 0.28); other behaviours that were observed, such as aggression or handling of prey, could not be distinguished. Model limitations and potential improvements are discussed. The workflow design presented in this study can facilitate model development, be adapted to a wide range of species, and together with the appropriate measurements, can foster the study of behaviour and habitat use of free living animals throughout their annual routine.
139 citations
TL;DR: Large differences in flow-assistance are found between the equations, particularly with increasing lateral flow and increasingly supportive axial flow, and it is found that the behavioral strategy assumed is generally more influential on the perception of flow-Assistance than a small amount of uncertainty in the specification of an animal's speed.
78 citations
TL;DR: In this paper, the identification of marine areas of importance for seabirds is a challenge, because it is often unclear how birds are using the different areas in which they occur.
58 citations
TL;DR: It is concluded that along migration corridors with generally nonsupportive winds, juvenile passerines should not strictly select supportive winds but partially compensate for drift to increase their chances for timely and accurate arrival.
Abstract: A migrating bird’s response to wind can impact its timing, energy expenditure, and path taken. The extent to which nocturnal migrants select departure nights based on wind (wind selectivity) and compensate for wind drift remains unclear. In this paper, we determine the effect of wind selectivity and partial drift compensation on the probability of successfully arriving at a destination area and on overall migration speed. To do so, we developed an individual-based model (IBM) to simulate full drift and partial compensation migration of juvenile Willow Warblers (Phylloscopus trochilus) along the southwesterly (SW) European migration corridor to the Iberian coast. Various degrees of wind selectivity were tested according to how large a drift angle and transport cost (mechanical energy per unit distance) individuals were willing to tolerate on departure after dusk. In order to assess model results, we used radar measurements of nocturnal migration to estimate the wind selectivity and proportional drift among passerines flying in SW directions. Migration speeds in the IBM were highest for partial compensation populations tolerating at least 25% extra transport cost compared to windless conditions, which allowed more frequent departure opportunities. Drift tolerance affected migration speeds only weakly, whereas arrival probabilities were highest with drift tolerances below 20°. The radar measurements were indicative of low drift tolerance, 25% extra transport cost tolerance and partial compensation. We conclude that along migration corridors with generally nonsupportive winds, juvenile passerines should not strictly select supportive winds but partially compensate for drift to increase their chances for timely and accurate arrival.
57 citations
TL;DR: It is concluded that the high degree of standardisation in the NDFF data model has led to somewhat increased cost in data conversion, but also to improved semantic integration and ease-of-use of species observation data.
10 citations