Landscape structure constrains the dispersal of a mobile songbird: a paradox?
Friday Seminar by Erik Matthysen.
Small songbirds have intrinsically high locomotory capacities compared to other organisms of the same body size, and therefore movement patterns could be expected to be relatively insensitive to fine-grained landscape structure. Nevertheless, many songbird species have restricted dispersal and respond negatively to isolation of habitat patches. To better understand the relationship between landscape structure, movement behaviour and realized disperal, we studied daily movements as well as dispersal of a forest-restricted passerine, the Great Tit Parus major, in a study area of 10 km2 containing 15 forest patches of 1 to 15 ha. Birds are physically able to fly across the entire area in less than an hour, and winter observations showed that individual birds commute daily between roosting and feeding sites over distances of 500 m or more. Despite this high mobility, we found several indications that dispersal is not neutral with respect to fine-grained landscape structure. First of all, up to 30% of birds (depending on species and sex) never left their natal forest patch, and this proportion was significantly higher compared to similar study plots embedded in larger forest. Secondly, dispersal between forest patches was positively related to an index of between-patch connectivity (based on least-cost paths). Thirdly, dispersal directions were spatially autocorrelated, i.e. birds born in nearby nestboxes moved in similar directions, presumably in response to the surrounding landscape structure. We hypothesize that the influence of landscape structure on dispersal reflects settlement decisions taken early in life when birds are less mobile. In particular, we discuss the potential impact of early experiences gained during family movements.
Prof. Dr. Erik Matthysen
Evolutionary Ecology Group, New research group starting January 1st 2008
Department of Biology, University of Antwerp
The CEES seminar room has a coffee-machine – it is therefore recommended that you come a bit earlier and get yourself a good cup of coffee (for the price of 3 NOK).