Interspecific Comparison of the Performance of Soaring Migrants in Relation to Morphology, Meteorological Conditions and Migration Strategies

Peer reviewe

Density-dependence across dispersal stages in a hermaphrodite land snail: insights from discrete choice models

International audienceDispersal movements, i.e. movements leading to gene flow, are key behaviours with important, but only partially understood, consequences for the dynamics and evolution of populations. In particular, density-dependent dispersal has been widely described, yet how it is determined by the interaction with individual traits, and whether density effects differ between the three steps of dispersal (departure, transience, and settlement), remains largely unknown. Using a semi-natural landscape, we studied dispersal choices of Cornu aspersum land snails, a species in which negative effects of crowding are well documented, and analysed them using dispersal discrete choice models, a new method allowing the analysis of dispersal decisions by explicitly considering the characteristics of all available alternatives and their interaction with individual traits. Subadults were more dispersive than adults, confirming existing results. In addition, departure and settlement were both density dependent: snails avoided crowded patches at both ends of the dispersal process, and subadults were more reluctant to settle into crowded patches than adults. Moreover, we found support for carry-over effects of release density on subsequent settlement decisions: snails from crowded contexts were more sensitive to density in their subsequent immigration choices. The fact that settlement decisions were informed indicates that costs of prospecting are not as important as previously thought in snails, and/or that snails use alternative ways to collect information, such as indirect social information (e.g. trail following). The observed density-dependent dispersal dynamics may play an important role in the ability of C. aspersum to successfully colonise frequently human-disturbed habitats around the world

Discrete choice modelling of natal dispersal: 'Choosing' where to breed from a finite set of available areas

© 2015 British Ecological Society. Classic natal dispersal studies focus mainly on distance travelled. Although distances capture some of the main selective pressures related to dispersal, this approach cannot easily incorporate the properties of the actual destination vs. the available alternatives. Recently, movement ecology studies have addressed questions on movement decisions in relation to availability of resources and/or availability of suitable habitats through the use of discrete choice models (DCMs), a widely used type of models within econometrics, which explains individual choices as a function of the properties of a finite number of alternatives. In this contribution, we show how the dispersal discrete choice model (DDCM) can be used for analysing natal dispersal data in patchy environments given that the natal and the breeding area of the disperser are observed. We test this method using a case study on Great Tits (Parus major) in an archipelago of small woodlots. Our results show that DDCMs are able to capture the results of classic distance-based approaches and simultaneously allow testing hypotheses on how departure and settlement are affected by variables that characterize the disperser, the natal patch and the breeding area, as well as their interactions. DDCMs can be applied to any other species and system that uses some form of discrete breeding location or a certain degree of discretization can be applied.status: publishe

Data from: Discrete choice modelling of natal dispersal: "choosing" where to breed from a finite set of available areas

1. Classic natal dispersal studies focus mainly on distance travelled. Although distances capture some of the main selective pressures related to dispersal, this approach cannot easily incorporate the properties of the actual destination vs. the available alternatives. Recently, movement ecology studies have addressed questions on movement decisions in relation to availability of resources and/or availability of suitable habitats through the use of discrete choice models (DCMs), a widely used type of models within econometrics, which explains individual choices as a function of the properties of a finite number of alternatives. 2. In this contribution, we show how the dispersal discrete choice model (DDCM) can be used for analysing natal dispersal data in patchy environments given that the natal and the breeding area of the disperser are observed. We test this method using a case study on Great Tits (Parus major) in an archipelago of small woodlots. 3. Our results show that DDCMs are able to capture the results of classic distance-based approaches and simultaneously allow testing hypotheses on how departure and settlement are affected by variables that characterize the disperser, the natal patch and the breeding area, as well as their interactions. 4. DDCMs can be applied to any other species and system that uses some form of discrete breeding location or a certain degree of discretization can be applied

Raw data from Parus.Database

This an RData file with the raw data extract from the Parus Database that managed by Frank Adriaensen. For further information please contact [email protected]

Mean daily distances (±1 SE; N = 547 segments) per season and species.

<p>Sample sizes are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039833#pone.0039833.s002" target="_blank">table S2</a>.</p

Spatial and temporal variation of wind assistance (all species pooled).

<p>The maps show daily segments. Colours indicate the extent of wind support: green  =  tailwind (>2.5 m/s), blue  =  weak wind (2.5 to –2.5 m/s), red  =  headwind (< –2.5 m/s). The bars show the frequency of different tailwind classes in different latitudinal bands.</p

GLM mixed model with daily distance as dependent variable, including all data.

<p>GLM mixed model with daily distance as dependent variable, including all data.</p

Migration tracks of raptors crossing the Sahara desert.

<p>Each segment connects two roosting locations. Spring tracks are on the left and autumn tracks on the right. The colours of the segments indicate the species as Osprey (blue), Marsh Harrier (green), Egyptian Vulture (orange), or Short-toed Eagle (red). Black arrows represent average wind directions (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039833#s2" target="_blank">Results</a>). Sample sizes are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039833#pone-0039833-t001" target="_blank">table 1</a>.</p

Time budgets and sample sizes in relation to time of day (<i>N</i> = 2835).

<p>Coloured parts indicate travelling segments, while grey parts represent stopping segments. Morning includes period 1 and 2, midday period 3 and 4, and afternoon 5 and 6 (see Methods).</p