Building multiple nests is associated with reduced breeding performance in a south temperate population of Grass Wrens Cistothorus platensis platensis

LLAMBÍAS, P; JEFFERIES MM; CÁCERES APAZA D; GARRIGO PS; A ZARCO; ARRIETA RS; BENDER B

IBIS

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020

0019-1019

Grass Wrens Cistothorus platensis build more neststructures than are used for breeding. We used a nest-removal experiment and observationaldata to evaluate several hypotheses regarding the adaptive significance ofbuilding multiple nests in a south temperate population of Grass Wrens. Buildingnon-breeding nests was not a strategy of males to attract additional females asmost of these nests were built after pair formation and both sexes collaboratedduring building. Building non-breeding nests was not a post-pairing display asthe presence of multiple nests did not increase female investment in the breeding attempt: clutchsize and female provisioning to nestlings did not differ between experimentaland control territories where no non-breeding nests were removed. Similarly, innon-manipulated territories, clutch size and female provisioning were not correlatedwith the number of non-breeding nests or with males? nest building effort. Contraryto this hypothesis, the number of non-breeding nests was associated withdelayed clutch initiation and reduced hatching success. The presence ofnon-breeding nests did not reduce nest predation and brood parasitism, which didnot differ between experimental and control territories. We did not detectdifferences in concealment between non-breeding and breeding nests, suggestingthat non-breeding nests were not the result of abandonment before egg-laying toreduce subsequent nest predation. Dummy nests didnot provide shelter; they were not frequently used for roosting over thebreeding season and were not maintained during the non-breeding season. Wesuggest that building non-breeding nests may be attempts by males to manipulatethe decision of females to breed with a mate they might otherwise reject or tostart reproduction earlier than optimal for them.