Vlieggedrag in beeld: vogels met GPS-rugzakje

De Universiteit van Amsterdam heeft een miniatuur GPS-rugzakje ontwikkeld om het gedrag van vogels te bestuderen. Een zonnepaneel, batterijlader en batterij, een GPS-ontvanger en -antenne, een processor en geheugen, een sensor om de vleugelslagfrequentie te meten, en een Radiozender en ontvanger, alles bij elkaar maar twaalf gram

Seed dispersal as a search strategy: dynamic and fragmented landscapes select for multi-scale movement strategies in plants

Background Plant dispersal is a critical factor driving ecological responses to global changes. Knowledge on the mechanisms of dispersal is rapidly advancing, but selective pressures responsible for the evolution of dispersal strategies remain elusive. Recent advances in animal movement ecology identified general strategies that may optimize efficiency in animal searches for food or habitat. Here we explore the potential for evolution of similar general movement strategies for plants. Methods We propose that seed dispersal in plants can be viewed as a strategic search for suitable habitat, where the probability of finding such locations has been optimized through evolution of appropriate dispersal kernels. Using model simulations, we demonstrate how dispersal strategies can optimize key dispersal trade-offs between finding habitat, avoiding kin competition, and colonizing new patches. These trade-offs depend strongly on the landscape, resulting in a tight link between optimal dispersal strategy and spatiotemporal habitat distribution. Results Our findings reveal that multi-scale seed dispersal strategies that combine a broad range of dispersal scales, including Lévy-like dispersal, are optimal across a wide range of dynamic and patchy landscapes. At the extremes, static and patchy landscapes select for dispersal strategies dominated by short distances, while uniform and highly unpredictable landscapes both select for dispersal strategies dominated by long distances. Conclusions By viewing plant seed dispersal as a strategic search for suitable habitat, we provide a reference framework for the analysis of plant dispersal data. Consideration of the entire dispersal kernel, including distances across the full range of scales, is key. This reference framework helps identify plant species’ dispersal strategies, the evolutionary forces determining these strategies and their ecological consequences, such as a potential mismatch between plant dispersal strategy and altered spatiotemporal habitat dynamics due to land use change. Our perspective opens up directions for future studies, including exploration of composite search behaviour and ‘informed searches’ in plant species with directed dispersal

Seed dispersal distributions resulting from landscape-dependent daily movement behavior of a key vector species, Anas platyrhynchos

Dispersal via animals (zoochory) is a primary mechanism for seed exchange between habitat patches. Recent studies have established that many plant species can survive waterbird gut passage. To quantify the patterns and consequences of waterbird-mediated dispersal, information on ingestion and gut passage must be combined with bird movement data. Such analysis has recently revealed seed dispersal kernels by migrating waterbirds. However, since many waterbird populations are largely resident, and migrating populations spend only a minor part of the main dispersal season (autumn–winter) on active migration, daily regional-scale movements probably cause more frequent dispersal. We synthesized high-resolution empirical data on landscape-scale movements and seed gut passage times in a key disperser species, the mallard (Anas platyrhynchos), using a spatially explicit, mechanistic model to quantify dispersal distributions resulting from daily autumn–winter movements. We evaluated how landscape composition and seed traits affect these dispersal patterns. The model indicates that mallards generate highly clumped seed deposition patterns, dispersing seeds primarily between core areas used for foraging and resting. Approximately 34% of all dispersed seeds are transported to communal roost areas, which may function as reservoirs for mallard-dispersed species, and 7% are transported between foraging areas. Landscape-dependent movement patterns strongly affect the dispersal distributions, resulting in multi-modal dispersal kernels, with dispersal distances increasing with fragmentation of freshwater foraging habitat. Seed size-related gut retention times determine the proportion of seeds being dispersed away from the ingestion area, with larger seeds (20 mm3) having a 8–10% higher potential for long-distance dispersal than smaller seeds (0·2 mm3), if surviving gut passage. However, twice as many small seeds will finally accomplish long-distance dispersal due to their higher gut passage survival. Synthesis. Firstly, this study reveals how seed dispersal patterns resulting from daily waterfowl movements are shaped by landscape-dependent differences in movement patterns. Secondly, seed survival appears more important than retention time in determining the scale of long-distance dispersal by non-migrating mallards. We conclude that the frequent flights of staging waterbirds result in directed dispersal over distances inversely related to wetland availability, indicating that they maintain landscape connectivity across a range from wet to increasingly dry landscapes

Seed dispersal distributions resulting from landscape-dependent daily movement behavior of a key vector species, <em>Anas platyrhynchos</em>

Dispersal via animals (zoochory) is a primary mechanism for seed exchange between habitat patches. Recent studies have established that many plant species can survive waterbird gut passage. To quantify the patterns and consequences of waterbird-mediated dispersal, information on ingestion and gut passage must be combined with bird movement data. Such analysis has recently revealed seed dispersal kernels by migrating waterbirds. However, since many waterbird populations are largely resident, and migrating populations spend only a minor part of the main dispersal season (autumn–winter) on active migration, daily regional-scale movements probably cause more frequent dispersal.We synthesized high-resolution empirical data on landscape-scale movements and seed gut passage times in a key disperser species, the mallard (Anas platyrhynchos), using a spatially explicit, mechanistic model to quantify dispersal distributions resulting from daily autumn–winter movements. We evaluated how landscape composition and seed traits affect these dispersal patterns.The model indicates that mallards generate highly clumped seed deposition patterns, dispersing seeds primarily between core areas used for foraging and resting. Approximately 34% of all dispersed seeds are transported to communal roost areas, which may function as reservoirs for mallard-dispersed species, and 7% are transported between foraging areas. Landscape-dependent movement patterns strongly affect the dispersal distributions, resulting in multi-modal dispersal kernels, with dispersal distances increasing with fragmentation of freshwater foraging habitat. Seed size-related gut retention times determine the proportion of seeds being dispersed away from the ingestion area, with larger seeds (20 mm3) having a 8–10% higher potential for long-distance dispersal than smaller seeds (0·2 mm3), if surviving gut passage. However, twice as many small seeds will finally accomplish long-distance dispersal due to their higher gut passage survival.Synthesis. Firstly, this study reveals how seed dispersal patterns resulting from daily waterfowl movements are shaped by landscape-dependent differences in movement patterns. Secondly, seed survival appears more important than retention time in determining the scale of long-distance dispersal by non-migrating mallards. We conclude that the frequent flights of staging waterbirds result in directed dispersal over distances inversely related to wetland availability, indicating that they maintain landscape connectivity across a range from wet to increasingly dry landscapes

Using high resolution GPS tracking data of bird flight for meteorological observations

Bird flight is strongly influenced by local meteorological conditions. With increasing amounts of high-frequency GPS data of bird movement becoming available, as tags become cheaper and lighter, opportunities are created to obtain large datasets of quantitative meteorological information from observations conducted by bird-borne tags. In this article we propose a method to estimate wind velocity and convective velocity scale from tag-based high-frequency GPS data of soaring birds in flight.The flight patterns of soaring birds are strongly influenced by the interactions between atmospheric boundary layer processes and the morphology of the bird; climb rates depend on vertical air motion, flight altitude depends on boundary layer height, and drift off the bird?s flight path depends on wind speed and direction. We combine aerodynamic theory of soaring bird flight, the bird?s morphological properties and three-dimensional GPS measurements at 3-seconds intervals to estimate the convective velocity scale and horizontal wind velocity at the locations and times of flight.We use wind speed and direction observations from meteorological ground stations and estimates of convective velocity from the Ocean-Land-Atmosphere Model (OLAM) to evaluate our findings. Although not colocated, our wind velocity estimates are consistent with ground station data, and convective velocity scale estimates are consistent with the meteorological model. Our work demonstrates that biologging offers a novel alternative approach for estimating atmospheric conditions on a spatial and temporal scale that complement existing meteorological measurement systems