Migrant birds and mammals live faster than residents

Billions of vertebrates migrate to and from their breeding grounds annually, exhibiting astonishing feats of endurance. Many such movements are energetically costly yet there is little consensus on whether or how such costs might influence schedules of survival and reproduction in migratory animals. Here we provide a global analysis of associations between migratory behaviour and vertebrate life histories. After controlling for latitudinal and evolutionary patterns, we find that migratory birds and mammals have faster paces of life than their non-migratory relatives. Among swimming and walking species, migrants tend to have larger body size, while among flying species, migrants are smaller. We discuss whether pace of life is a determinant, consequence, or adaptive outcome, of migration. Our findings have important implications for the understanding of the migratory phenomenon and will help predict the responses of bird and mammal species to environmental changeinfo:eu-repo/semantics/publishedVersio

Reduced Dependence of Crested Ibis on Winter-Flooded Rice Fields: Implications for Their Conservation

<div><p>The Crested Ibis <i>Nipponia nippon</i> was once thought to be extinct in the wild until seven birds were discovered in a remote mountain village in China in 1981. Studies suggested that winter-flooded rice fields play an essential role in nest site selection by the Crested Ibis and hence in their survival. Considerable efforts were therefore made to conserve the winter-flooded rice fields, but these have caused conflicts between the agricultural and conservation communities. The population and geographical range of the wild Crested Ibis has expanded greatly since 1981, but there is no spatial information on the winter-flooded rice fields, nor on the current association of nest sites and winter-flooded rice fields. We mapped winter-flooded rice fields across the entire current range of Crested Ibis using innovative remote sensing and geographical information systems (GIS) techniques. The spatial relationships between the nest site clusters and winter-flooded rice fields were quantified using Ward's hierarchical clustering method and Ripley's K-function. We show that both have significantly clumped distribution patterns and that they are positively associated. However, the dependence of Crested Ibis on the winter-flooded rice fields varied significantly among the nest site clusters and has decreased over the years, indicating the absence of winter-flooded rice fields is not constraining their recovery and population expansion. We therefore recommend that efforts should be made to protect the existing winter-flooded rice fields and to restore the functionality of natural and semi-natural wetlands, to encourage both <i>in-situ</i> conservation and the re-introduction of the Crested Ibis. In addition, we recommend that caution should be exercised when interpreting the habitat requirements of species with a narrow distribution, particularly when that interpretation is based only on their current habitat.</p></div

Map of the study area.

<p>The locations of nest sites of the Crested Ibis in 1981 and 2009 are marked.</p

Differences in the area of winter-flooded rice fields in the nest site clusters.

<p>The area of winter-flooded rice fields within 3-km buffers around the nest sites in the five clusters (A–E) is shown by box plots. The only pair with no significant difference is annotated based on pairwise Mann-Whitney U tests (<i>P</i>≥0.05).</p

Nest site clusters and the extent of winter-flooded rice fields.

<p>Five clusters (A–E) were identified based on their geographical locations, using Ward's hierarchical clustering method. They are shown in different colours. The extent of winter-flooded rice fields within 3-km buffers around the nest sites are delineated by circles of three different sizes (high, medium and low). The locality name and year when the first nest site was established in each cluster are given above and below the line, with the total number of nests per cluster in parentheses.</p

Variations in the spatial association between nest sites and winter-flooded rice fields over the years.

<p>Observed L-function values from bivariate L-function analysis for the five nest site clusters (A–E) established over the years are shown by box plots. The only pair with no significant difference is annotated based on post-hoc pairwise Tukey's HSD test (<i>P</i>≥0.05).</p

Spatial association between nest sites and winter-flooded rice fields in the nest site clusters.

<p>Bivariate L-function L₁₂(r) against distance r for each cluster is plotted (A–E). Solid lines are observed values of L₁₂(r). Dotted and dashed lines are the theoretical values and the 95% confidence envelopes, respectively, for the pattern expected under the null hypothesis of population independence. Values of L₁₂(r) above the upper envelope indicate a significant positive association, whereas values of L₁₂(r) below the lower envelope indicate a significant negative association. The year when the nest site was first established in the cluster is given.</p

Plot of univariate L-function against distance r showing the spatial pattern.

<p>A. Distribution of nest sites. B. Distribution of winter-flooded rice fields. Solid lines are observed values of L(r). Dotted and dashed lines are the theoretical values and the 95% confidence envelopes, respectively, for the pattern expected from a random distribution. Values of L(r) above the upper envelope indicate a significantly clumped distribution at distance r. Values of L(r) below the lower envelope indicate a significantly regular distribution at distance r.</p

Land cover/land use map generated by the hybrid classifier.

<p>The inset shows a zoomed-in map of a specific sample area.</p

Plot of bivariate L-function for the spatial association between nest sites and winter-flooded rice fields.

<p>Solid lines are observed values of L₁₂(r). Dotted and dashed lines are the theoretical values and the 95% confidence envelopes, respectively, for the pattern expected under the null hypothesis of population independence. Values of L₁₂(r) above the upper envelope indicate a significant positive association, whereas values of L₁₂(r) below the lower envelope indicate a significant negative association.</p