RT Journal Article T1 Helpers during replacement clutches buffer the impacts of late breeding on a cooperative bird A1 de la Cruz, Carlos A1 Valencia-Ruiz, Juliana A1 Expósito-Granados, Mónica A1 Solís, Elena A1 Jiménez, Olga A1 Alarcos, Susana A1 Abad-Gómez, José María A1 García-Baquero, María Jesús A1 Gutiérrrez, Jorge S. K1 Aves - Nidos AB Renesting is an important strategy employed by many bird species to compensate for nest failure. However, although replacement clutches may increase an individual's annual reproductive success, they impose substantial energetic and fitness costs. In some cooperatively breeding species, helpers lighten breeders' workloads thereby facilitating a second clutch within a season or increasing their survival prospects. Alternatively, renesting may increase the chances of having help in replacement clutches as some individualsthat have lost their own clutch could redirect their parental effort to another nest. Herewe used a 20-year dataset of a facultative cooperative breeder, the Iberian magpie, Cyanopica cooki, to investigate how helping and renesting behaviours combine to affect reproductive output. After controlling for clutch size and laying date, we show that helpers had a positive effect on the reproductive success of pairs, particularly in replacement clutches. Indeed, our study revealed that replacement clutches were much more commonthan previously thought (observed in three-quarters of the females that lost the first clutch), and that the probability of receiving help was higher in replacement clutches. As helpers increased in number over the breeding season, they could contribute to buffering the negative effects of breeding late, when environmental conditions can be more adverse, and the probability of successful independent reproduction is lower. This study indicates that species with cooperative breeding and a short lifespan can prioritize currentover future reproduction by renesting at the end of the breeding season, when the benefits of having help outweigh the costs associated with deteriorating environmental conditions.We propose that renesting can be a context-dependent strategy (mediated by social and environmental factors) that may increase reproductive success in avian cooperative breeding systems. PB Elsevier YR 2022 FD 2022 LK https://hdl.handle.net/10630/45543 UL https://hdl.handle.net/10630/45543 LA eng NO de la Cruz, C., Valencia, J., Expósito-Granados, M., Solís, E., Jiménez, O., Alarcos, S., Abad-Gómez, J. M., García-Baquero, M. J. y Gutiérrez, J. S. (2022). Helpers during replacement clutches buffer the impacts of late breeding on a cooperative bird. Animal Behaviour, 184, 43-53 NO This study was supported by the Government of Extremadura, cofinanced by FEDER Funds through the projects IPR99A020, 2PR02A080, PRI09A057 and PRI09A057 to C.C. and funds for research group GR15117 to M.E-G. and O.J. and J.V. was supported by a postdoctoral grant from Ministerio de Educaci on y Ciencia of Spain and CSIC grant (JAEdoc); E.S. was supported by a postgraduate research grant from Junta de Extremadura; and J.S.G. was supported by the Government of Extremadura (grant no. TA18001). DS RIUMA. Repositorio Institucional de la Universidad de Málaga RD 25 feb 2026