Helpers increase daily survival rate of Southern Lapwing (Vanellus chilensis) nests during the incubation stage

Abstract

Cooperative breeding is characterized by reproduction in the presence of helpers. What impact these helpers have on the reproductive success of group members is one of the long-standing questions in the cooperative breeding literature. In cooperative species, helpers are known to provide benefits during multiple stages or at a particular stage of the reproductive cycle. The aim of this study was to investigate whether helpers increased the daily survival rate of nests during the incubation stage in the Southern Lapwing (Vanellus chilensis), a crested plover with a cooperative breeding system. Southern Lapwings have a variable mating system, with some breeding groups composed of unassisted pairs, and others that breed in the presence of helpers. Our best supported model indicated a positive effect of the presence of helpers on the daily survival rate of nests, leading to a probability of nest success (i.e., survival until hatching) of 83%, compared to 51% for nests of unassisted pairs. But a null model had a similar model weight as the best supported model and was the second-best model. Our study provides evidence that helpers influence egg survival during the egg-incubation stage, which could influence the fitness of breeders.