NEST PREDATION AND REPRODUCTIVE TRAITS IN SMALL PASSERINES - A COMPARATIVE APPROACH

Nest predation can be a decisive factor in the evolution of bird repro duction strategies. This paper compares several reproductive traits in small passerines on the Iberian Peninsula (n = 31) with the probabili ty of daily nest survival from predation. We consider the phylogenetic relationships between species by means of an analysis according to th ree models of evolutionary change: Brownian, punctuational and GRAFEN' s arbitrary. In this comparative evolutionary scenario, clutch size, e gg volume and incubation period appear not to change in relation to ne st predation, while the nestling phase duration is a positively-relate d parameter to daily nest survival from predation. These results are c onsistent for all models of evolutionary change. Thus, from the perspe ctive of nest predation, the nestling period is the most important evo lutionary parameter in small passerines. A hypothetical influence of n est predation on passerine clutch and egg size should only be regarded as an indirect factor, linked to the relationship between these param eters and the duration of the nestling period.