BUSCADOR RECOLECTA

Host defences against cuckoo parasitism and cuckoo trickeries to overcome them are a classic example of antagonistic coevolution. Recently it has been reported that this relationship may turn to be mutualistic in the case of the carrion crow (Corvus corone) and its brood parasite, the great spotted cuckoo (Clamator glandarius), given that experimentally and naturally parasitized nests were depredated at a lower rate than non-parasitized nests. This result was interpreted as a consequence of the antipredatory properties of a fetid cloacal secretion produced by cuckoo nestlings, which presumably deters predators from parasitized host nests. This potential defensive mechanism would therefore explain the detected higher fledgling success of parasitized nests during breeding seasons with high predation risk. Here, in a different study population, we explored the expected benefits in terms of reduced nest predation in naturally and experimentally parasitized nests of two different host species, carrion crows and magpies (Pica pica). During the incubation phase non-parasitized nests were depredated more frequently than parasitized nests. However, during the nestling phase, parasitized nests were not depredated at a lower rate than non-parasitized nests, neither in magpie nor in carrion crow nests, and experimental translocation of great spotted cuckoo hatchlings did not reveal causal effects between parasitism state and predation rate of host nests. Therefore, our results do not fit expectations and, thus, do not support the fascinating possibility that great spotted cuckoo nestlings could have an antipredatory effect for host nestlings, at least in our study area. We also discuss different possibilities that may conciliate these with previous results, but also several alternative explanations, including the lack of generalizability of the previously documented mutualistic association., Peer reviewed

Support by funding was provided by Spanish Ministerio de Ciencia e Innovación, European funds (FEDER) (CGL2009-14006, CGL2010-19233-C03-01, CGL2010-19233-C03-03, CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P) and Junta de Andalucía (P09-RNM-4557). AM-G had a predoctoral grant from the Junta de Andalucía (P09-RNM-4557)., Peer reviewed

En la tabla se indican características de los nidos y pollos de estornino negro (Sturnus unicolor) utilizados en el artículo: Juan J. Soler, Cristina Ruiz-Castellano, Jordi Figuerola, Josué Martínez-de la Puente, Magdalena Ruiz-Rodríguez and Gustavo Tomás (2018) Egg colouration predicts brood size, telomere length and body condition of spotless starling fledglings. Journal of Avian Biology, e01686. doi: 10.1111/jav.01686 Nest identity: identidad de los nidos utilizados . feather treatment: si se añadieron plumas a los nidos durante el crecimiento de los pollos o no. plant treatment: si se añadieron plantas verdes a los nidos durante el crecimiento de los pollos o no. Brightness: Brillo (luminosidad) de los huevos de estorninos de los distintos nidos. Blue-Green chroma (400-580): Croma verde-azulado, reflectancia en longitudes de onda. comprendidas entre 400 y 580 nm dividida por la reflectanca de todo el espectro (300-700nm) en tanto por ciento. hathing date (1=1st april): fecha de eclosion (el valor 1 corresponde al 1 de abril). Clutch size: tamaño de puesta. Brood size: tamaño de pollada. Body mass: peso corporal de pollos de 14 dias de edad. Tarsus length: longitude del tarso de pollos de 14 días de edad. Body condition: condicion corporal de pollos de 14 días de edad estimada como los residuos del peso después de controlar por la longitud del tarso. Telomere length (hatchlings): longitud de los telómeros de pollos recién eclosionados. Telomere length (fledglings): longitude de los telómeros de pollos poco antes de abandonar el nido., Para la recogida de los datos se ha seguido la reproducción de dos poblaciones de estornino negro. Además de anotar información sobre distintas variables reproductoras (fecha de puesta, taño de puesta y de pollada,, y éxito reproductor, se ha medido el color de sus huevos, se han tomado muestras de sangre de pollos recién eclosionados y poco antes de abandonar el nido. También se midió el tarso y el peso corporal de los pollos poco antes de abandonar el nido. La estima del tamaño de los telomeros se realizó en el laboratorio, a partir de ADN de los glóbulos rojos de las muestras de sangre recogidas en el campo., Funding was provided by the Spanish Ministerio de Economia y Competitividad and European funds (FEDER) (CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P, CGL2012-30759, CGL2015-65055-P). JMP, GT and MRR were supported by Juan de la Cierva, Ramón & Cajal and Talentia postdoctoral contracts, respectively. JMP was partially supported by a 2017 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation., Peer reviewed