Conspecific attraction and the scaling of bird nest spatial patterns and local abundances

JOVANI, R.; LANERI, K.; ROZENFELD, A.F.; TELLA, J.L.; ORO, D.

Scaling in Bird Coloniality

Estacion Biológica Doñana (CSIC), Universidad de Sevilla

Lugar: Sevilla; Año: 2006; p. 94 - 105

The spatial distribution of organisms is often patchy in nature. Herewe study one of the most spectacular animal patchy distributions:bird colonies. In bird coloniality research, the underlyingheterogeneity in habitat or individual behaviours is hypothesisedto be the main driver of the observed heterogeneity on spatialdistribution (location of nests/colonies) and local abundance (colonysizes) in colonial birds. Conspecific attraction [i.e. habitat selection(positively) driven by the presence of conspecifics], is a recognisednest clumping mechanism in birds. Here, we implemented anindividual-based model where nest site selection was driven byconspecific attraction in a homogeneous lattice (thus, the behaviourof birds and habitat suitability were homogeneous). The spatialdistribution of nests displayed by the model output was highlyheterogeneous, showing a fractal-like behaviour at intermediatescales, thus showing clusters at different resolutions. The cluster(colony) size frequency distribution followed a power law. Theseresults were very similar to those found for White storks in Doñana(SW Spain; Chapter 3), but greatly differed from those for Lesserkestrels in the Ebro Valley (NE Spain; Chapter 4). We discuss thepotential relevance of conspecific attraction in bird ecology andevolution, and propose power laws as a useful null model againstwhich to test patterns of spatial distribution and local abundance incolonial birds.