Scaling of Natal Dispersal Distances in Terrestrial Birds and Mammals

Abstract

ABSTRACT. Natal dispersal is a process that is critical in the spatial dynamics of populations, including population spread, recolonization, and gene flow. It is a central focus of conservation issues for many vertebrate species. Using data for 77 bird and 68 mammal species, we tested whether median and maximum natal dispersal distances were correlated with body mass, diet type, social system, taxonomic family, and migratory status. Body mass and diet type were found to predict both median and maximum natal dispersal distances in mammals: large species dispersed farther than small ones, and carnivorous species dispersed farther than herbivores and omnivores. Similar relationships occurred for carnivorous bird species, but not for herbivorous or omnivorous ones. Natal dispersal distances in birds or mammals were not significantly related to broad categories of social systems. Only in birds were factors such as taxonomic relatedness and migratory status correlated with natal dispersal, and then only for maximum distances. Summary properties of dispersal processes appeared to be derived from interactions among behavioral and morphological characteristics of species and from their linkages to the dynamics of resource availability in landscapes.In all the species we examined, most dispersers moved relatively short distances, and long-distance dispersal was uncommon. On the basis of these findings, we fit an empirical model based on the negative exponential distribution for calculating minimum probabilities that animals disperse particular distances from their natal areas. This model, coupled with knowledge of a species' body mass and diet type, can be used to conservatively predict dispersal distances for different species and examine possible consequences of large-scale habitat alterations on connectedness between populations. Taken together, our results can provide managers with the means to identify species vulnerable to landscape-level habitat changes such as forest fragmentation. In addition, our dispersal models can be used to predict which species in a community are likely to be the most vulnerable to loss of connectedness and allow managers to test the merits of alternative habitat conservation plans.

Urban Bird Diversity and Landscape Complexity: Species-environment Associations Along a Multiscale Habitat Gradient

“…Some evidence suggests that birds search for and select breeding territories for the following year during their postfledgling exploration (Baker 1993). Therefore, habitat attributes and proximity to the natal area will affect the occupancy of areas close to successful breeding sites (Baker 1993, Bolger et al 1997, Helzer and Jelinski 1999, Sutherland et al 2000.…”

“…We thus downweighted park area by the inverse of distance to account for the fact that the outermost rings were much larger than the innermost ring and to investigate the effect of distance from parks on birds. This inverse of distance weighting scheme assigned a decreasing, nonlinear weight to park area as a function of distance and was related to the theoretical expectation that species and guild occurrence should decrease nonlinearly with distance from "natural" areas, given the dispersal distance trends for several species of birds examined by Sutherland et al (2000). We found significant relationships between park area by distance metrics and the distributions of American Robins, Spotted Towhees, and shrub-and groundnesting species, but our results were not consistent with those of Bolger et al (1997), who created an urban exposure index by assigning an inverse weighting scheme to the proportion of developed land within each concentric ring around point counts located in "islands" of natural habitat, creating an urban exposure index.…”

Integrating across Life-History Stages: Consequences of Natal Habitat Effects on Dispersal

“…For example, interspecific comparisons indicate that body size is positively correlated with dispersal in both mammals (Sutherland et al 2000) and birds (Paradis et al 1998). In mammals, one of the classic studies on prox imal factors associated with dispersal followed individually marked Belding's ground squirrels (Spermophilus beldingi) in two populations (Holekamp 1984(Holekamp , 1986.…”

How Dispersal Limitation Shapes Species–Body Size Distributions in Local Communities

“…For our model of disa k persal limitation, we need to know how , the inverse a k dispersal distance, scales with body mass. Sutherland et al (2000) suggest an allometric scaling law for active dispersal distance:…”