BUSCADOR RECOLECTA

1. Mechanisms guaranteeing reliability of messages are essential in understanding the underlying
information and evolution of signals. Micro-organisms may degrade signalling traits and
therefore influence the transmitted information and evolution of these characters. The role of
micro-organisms in animal signalling has, however, rarely been investigated.
2. Here, we explore a possible role for feather-degrading bacteria driving the design of ornamental
throat feathers in male spotless starlings (Sturnus unicolor). We estimated length, bacterial
load, degradation status and susceptibility to degradation by keratinolytic bacteria in
those feathers, compared with non-ornamental adjacent feathers in males, as well as to throat
feathers in females. In addition, the volume of the uropygial gland and its secretion was measured
and the secretion extracted. We also experimentally evaluated the capacity of each secretion
to inhibit growth of a keratinolytic bacterium.
3. The apical part of male ornamental throat feathers harboured more bacteria and degraded
more quickly than the basal part; these patterns were not detected in female throat feathers or
in non-ornamental male feathers. Moreover, degradation status of male and female throat
feathers did not differ, but was positively associated with feather bacterial density. Finally, the
size of the uropygial gland in both males and females predicted volume and the inhibitory
capacity of secretion against feather-degrading bacteria. Only in males was uropygial gland
size negatively associated with the level of feather degradation.
4. All results indicate differential susceptibility of different parts of throat feathers to keratinolytic
bacterial attack, which supports the possibility that throat feathers in starlings reflect individual
ability to combat feather-degrading bacteria honestly. This is further supported by the
relationship detected between antimicrobial properties of uropygial secretion and the level of
feather degradation.
5. Our results suggest that selection pressures exerted by feather-degrading bacteria on hosts
may promote evolution of particular morphologies of secondary sexual traits with different
susceptibility to bacterial degradation that reliably inform of their bacterial load. Those results
will help to understand the evolution of ornamental signals., This work was financed by Spanish Ministerio de Ciencia e Innovaci on, European
funds (FEDER) (CGL2010-19233-C03-01, CGL2013-48193-C3-1-P). MRR and DMG received a postdoc from the program “JAE-Doc”, GT from the “Juan de la Cierva”, and CRC had a predoctoral fellowship, all from the Spanish Government., Peer reviewed

Oily secretions produced in the uropygial gland of incubating female hoopoes contain antimicrobial-producing bacteria that prevent feathers from degradation and eggs from pathogenic infection. Using the beak, females collect the uropygial gland secretion and smear it directly on the eggshells and brood patch. Thus, some bacterial strains detected in the secretion should also be present on the eggshell, beak, and brood patch. To characterize these bacterial communities, we used Automatic Ribosomal Intergenic Spacer Analysis (ARISA), which distinguishes between taxonomically different bacterial strains (i.e. different operational taxonomic units [OTUs]) by the size of the sequence amplified.We identified a total of 146 different OTUs with sizes between 139 and 999 bp. Of these OTUs, 124 were detected in the uropygial oil, 106 on the beak surface, 97 on the brood patch, and 98 on the eggshell. The highest richness of OTUs appeared in the uropygial oil samples. Moreover, the detection of some OTUs on the beak, brood patch, and eggshells of particular nests depended on these OTUs being present in the uropygial oil of the female. These results agree with the hypothesis that symbiotic bacteria are transmitted from the uropygial gland to beak, brood patch, and eggshell surfaces, opening the possibility that the bacterial community of the secretion plays a central role in determining the communities of special hoopoe eggshell structures (i.e., crypts) that, soon after hatching, are filled with uropygial oil, thereby protecting embryos from pathogens., Support by funding was provided by Spanish Ministerio de Economía y Competitividad, European funds (FEDER) (CGL2013-48193-C3-1-P, CGL2013-48193-C3-3-P) and Junta de Andalucía (P09-RNM-4557).AM-G had a predoctoral grant from the Junta de Andalucía (P09-RNM-4557)., Peer reviewed

18 files are available from the NCBI GenBank database (accession number(s) KR076707 to KR076724, Molecular methods have revealed that symbiotic systems involving bacteria are mostly based on whole bacterial communities. Bacterial diversity in hoopoe uropygial gland secretion is known to be mainly composed of certain strains of enterococci, but this conclusion is based solely on culture-dependent techniques. This study, by using culture-independent techniques (based on the 16S rDNA and the ribosomal intergenic spacer region) shows that the bacterial community in the uropygial gland secretion is more complex than previously thought and its composition is affected by the living conditions of the bird. Besides the known enterococci, the uropygial gland hosts other facultative anaerobic species and several obligated anaerobic species (mostly clostridia). The bacterial assemblage of this community was largely invariable among study individuals, although differences were detected between captive and wild female hoopoes, with some strains showing significantly higher prevalence in wild birds. These results alter previous views on the hoopoe-bacteria symbiosis and open a new window to further explore this system, delving into the possible sources of symbiotic bacteria (e.g. nest environments, digestive tract, winter quarters) or the possible functions of different bacterial groups in different contexts of parasitism or predation of their hoopoe host., This work was supported by the Ministerio de Ciencia y Tecnología (projects CGL2005-06975/ BOSFEDER; CGL2007-61251/BOSFEDER), the Ministerio de Ciencia e Innovación (projects CGL2009-14006/BOSFEDER; CGL2010-19233-C03- 01/BOSFEDER; CGL2010-19233-C03-03/ BOSFEDER), the Ministerio de Economía y Competitividad (projects CGL2013-48193-C3-1-P/BOSFEDER; CGL2013-4819-C3-2-P/BOSFEDER), and the Junta de Andalucía (RNM 345, P09-RNM- 4557). SMRR received a grant from the Ministerio de Ciencia e Innovación (FPI program, BES-2011- 047677), Peer reviewed

Selective pressures imposed by pathogenic microorganisms to embryos have selected in hosts for a battery of antimicrobial lines of defenses that includes physical and chemical barriers. Due to the antimicrobial properties of volatile compounds of green plants and of chemicals of feather degrading bacteria, the use of aromatic plants and feathers for nest building has been suggested as one of these barriers. However, experimental evidence suggesting such effects is scarce in the literature. During two consecutive years, we explored experimentally the effects of these nest materials on loads of different groups of bacteria (mesophilic bacteria, Enterobacteriaceae, Staphylococcus and Enterococcus) of eggshells in nests of spotless starlings (Sturnus unicolor) at the beginning and at the end of the incubation period. This was also explored in artificial nests without incubation activity. We also experimentally increased bacterial density of eggs in natural and artificial nests and explored the effects of nest lining treatments on eggshell bacterial load. Support for the hypothetical antimicrobial function of nest materials was mainly detected for the year and location with larger average values of eggshell bacterial density. The beneficial effects of feathers and plants were more easily detected in artificial nests with no incubation activity, suggesting an active role of incubation against bacterial colonization of eggshells. Pigmented and unpigmented feathers reduced eggshell bacterial load in starling nests and artificial nest boxes. Results from artificial nests allowed us to discuss and discard alternative scenarios explaining the detected association, particularly those related to the possible sexual role of feathers and aromatic plants in starling nests. All these results considered together confirm the antimicrobial functionality mainly of feathers but also of plants used as nest materials, and highlight the importance of temporally and geographically environmental variation associated with risk of bacterial proliferation determining the strength of such effects. Because of costs associated to nest building, birds should adjust nest building effort to expected bacterial environments during incubation, a prediction that should be further explored., This work was financed by Spanish Ministerio de Ciencia e Innovación, European funds (FEDER) (CGL2010-19233-C03-01, CGL2010-19233-C03-03, CGL2013-48193-C3-1-P, CGL2013-48193-C3-3-P). MRR and DMG received a postdoc from the programmes “JAE-Doc” and CRC had a predoctoral grant from the Spanish Government. GT was supported by Juan de la Cierva programme (Spain)
and by Secretaría de Educación Superior, Ciencia, Tecnología e Innovación del Ecuador (SENESCYT)
through a Prometeo research grant., Peer reviewed

The study of associations between symbiotic bacterial communities of hosts and those of
surrounding environments would help to understand how bacterial assemblages are
acquired, and how they are transmitted from one to another location (i.e. symbiotic bacteria
acquisition by hosts). Hoopoes (Upupa epops) smear their eggshells with uropygial secretion
(oily secretion produced in their uropygial gland) that harbors antibiotic producing bacteria.
Trying to elucidate a possible role of nest material and cloaca microbiota in
determining the bacterial community of the uropygial gland and the eggshells of hoopoes,
we characterized bacterial communities of nest material, cloaca, uropygial gland and eggshells
by the ARISA fingerprinting. Further, by adding material with scarce bacteria and antimicrobial
properties, we manipulated the bacterial community of nest material and thus
tested experimentally its effects on the microbiomes of the uropygial secretion and of the
eggshells. The experiment did not influence the microbiome of the uropygial secretion of
females, but affected the community established on eggshells. This is the first experimental
evidence indicating that nest material influences the bacterial community of the eggshells
and, therefore, probability of embryo infection. Some of the bacterial strains detected in the
secretion were also in the bacterial communities of the nest material and of cloaca, but their
occurrence within nests was not associated, which suggests that bacterial environments of
nest material and cloaca are not sources of symbiotic bacteria for the gland. These results
do not support a role of nest environments of hoopoes as reservoirs of symbiotic bacteria.
We discuss possible scenarios explaining bacterial acquisition by hoopoes that should be
further explored, Support by funding was provided by Spanish Ministerio de Economía y Competitividad, European funds (FEDER) (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

How microbial symbionts are established and maintain on their hosts is a leading question with important consequences for the understanding of the evolution and functioning of mutualistic relationships. The acquisition by hosts of mutualistic microbial symbionts can be considered as colonization processes of environments (i.e., host) by symbionts. Colonization processes can be explored by characterizing the nestedness of communities, but this approach has rarely been applied to communities of microbial symbionts. We used this approach here, and estimated the nestedness of bacterial communities of hoopoes (Upupa epops), a species with symbiotic bacteria in their uropygial gland that are expected to colonize eggshells where they protect embryos from pathogens. Bacterial communities were characterized by ARISA (Automated rRNA Intergenetic Spacer Region) and studied the nestedness characteristics of bacterial communities living in the uropygial secretion, bill, belly and eggshells of each sampled female hoopoes. We detected a consistent nested pattern of bacterial communities of hoopoes; from the uropygial gland to the eggshell. We also found evidence of study year and reproductive events influencing the level of nestedness of bacterial communities of hoopoes. These results indicate that bacterial communities of eggshells and body parts of female hoopoes are at least partially conditioned by the symbiotic community in the uropygial gland. We discuss the importance of these results for understanding this host–microbial mutualism functioning and evolution, Support by funding was provided by Spanish Ministerio de Economía y Competitividad, European funds (FEDER) (CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P) and Junta de Andalucía (P09-RNM-4557). AMG had a PhD grant from the Junta de Andalucía (P09-RNM-4557)., Peer reviewed

Data available from the Dryad Digital Repository:
< http://dx.doi.org/10.5061/dryad.768vg > (Martín-Gálvez
and Soler 2016), The colouration of some traits in nestlings of altricial birds may influence parental food allocation as it may reflect physical condition or hunger. There is increasing evidence of the relationship between colouration of begging traits and nestling performance. However, evidence of the influence of hunger level on nestling colouration is scarce, mainly because of difficulty of distinguishing between the effects of physical condition and hunger levels. Here, we used the appetite stimulant cyproheptadine hydrochloride to increase the sensation of hunger of magpie Pica pica nestlings for eight days and assessed the effect on the colouration of rictal flanges, mouth and body skin. We found that nestlings administered with cyproheptadine had flanges more conspicuous (chromatic visual contrast), more UV coloured and less yellow coloured than their control nestmates. Conversely, mouths of experimental nestlings were more yellow coloured and less UV coloured
than controls. Our pharmacological experiment afected the strength of the relationship between body mass and some colour components of body skin (chromatic and achromatic visual contrasts, UV – chroma and yellow – chroma) and of rictal flanges (chromatic visual contrasts, UV – chroma and yellow – chroma), but not for mouth colouration. These results taken together suggest that the effect of the cyproheptadine on nestling colourations is probably mediated by an increase in hunger levels of nestlings for rictal flanges and body skin colourations, and by an increase in physical condition in the case of mouth coloration., Th is research was funded by a postdoctoral fellowship to DM-G from Ministerio de Educación y Ciencia, and by Ministerio de Ciencia e Innovación/FEDER (project CGL2013-48193-C3-1-P), Peer reviewed

Microorganisms have shaped the evolution of a variety of defense mechanisms against pathogenic infections. Radioactivity modifies bacterial communities and, therefore, bird hosts breeding in contaminated areas are expected to adapt to the new bacterial environment. We tested this hypothesis in populations of barn swallows (Hirundo rustica) from a gradient of background radiation levels at Chernobyl and uncontaminated controls from Denmark. Investment in defenses against keratinolytic bacteria was measured from feather structure (i.e., susceptibility to degradation) and uropygial secretions. We studied degradability of tail feathers from areas varying in contamination in laboratory experiments using incubation of feathers with a feather-degrading bacterium, Bacillus licheniformis, followed by measurement of the amount of keratin digested. The size of uropygial glands and secretion amounts were quantified, followed by antimicrobial tests against B. licheniformis and quantification of wear of feathers. Feathers of males, but not of females, from highly contaminated areas degraded at a lower rate than those from medium and low contamination areas. However, feathers of both sexes from the Danish populations showed little evidence of degradation. Individual barn swallows from the more contaminated areas of Ukraine produced the largest uropygial secretions with higher antimicrobial activity, although wear of feathers did not differ among males from different populations. In Denmark, swallows produced smaller quantities of uropygial secretion with lower antimicrobial activity, which was similar to swallow populations from uncontaminated areas in Ukraine. Therefore, barn swallows breeding in contaminated areas invested more in all defenses against keratinolytic bacteria than in uncontaminated areas of Ukraine and Denmark, although they had similar levels of feather wear. Strong natural selection exerted by radioactivity may have selected for individuals with higher defense capacity against bacterial infections during the 30 years since the Chernobyl disaster., M. Ruiz-Rodríguez had a Postdoc from the program “Andalucía Talent Hub” (Agencia Andaluza del Conocimiento, Junta de Andalucía). Funding was provided in part from the Samuel Freeman Charitable Trust, the US Fulbright Program, the CNRS (France), the American Council of Learned Societies, the University of South Carolina College of Arts and Sciences, and the Spanish Ministerio de Economía y Competitividad (European funds (FEDER)) (CGL2013-48193-C3-1-P)., Peer reviewed

Coevolutionary theory predicts that parasitism selects for defensive traits in the hosts that counteract the
negative effects of parasites. Such antagonistic interactions may continuously coevolve within cycles
without end, or result in host specialization and speciation of parasites. Here, we argue that particularities
of brood parasiteehost systems explain whether the coevolutionary relationships result in parasite specialization and speciation. Highlighted particularities of the system are (1) virulence of the parasites, (2) the ability of parasites to alter host behaviour, (3) the relative importance of defensive tolerance and defensive resistance of hosts, and (4) phenotypic plasticity of parasite virulence and host resistance. Fixed virulence of parasites selects for fixed resistance of hosts and both enhance the process of specialization and speciation of parasites. In contrast, phenotypic plasticity in virulence of the parasites would select for tolerance and facultative resistance in their hosts. These host characteristics imply limited escalation in resistance defences and therefore would facilitate continuous coevolutionary cycles preventing parasite specialization. Thus, when studying the diversification of brood parasites within the avian phylogeny, considering these three factors would help us understand what drives their evolution. To illustrate the importance of virulence, phenotypic plasticity and defensive tolerance for the evolution of parasites, we compare evolutionary radiation experienced by the genus Clamator and the Tribe Cuculinii, which includes the genus Cuculus, and speculate whether particularities of brood parasitism by the great spotted cuckoo, Clamator glandarius, and the common cuckoo, Cuculus canorus, explain differences in evolutionary radiation experienced by these two groups of brood parasites, we benefited from funding by the Spanish Ministerio de Ciencia e Innovación, Ministerio de Economía y Competitividad and European funds (FEDER) (project CGL2013-48193-C3-1-P) to J.J.S., and the Junta de Andalucía (project RNM610) to M.S., Peer reviewed

Nest materials used by animals can have profound effects on developing offspring. They can modify the bacterial and parasitic environment of the nest, and can influence parental investment through sexual signalling processes. In spotless starlings, Sturnus unicolor, green plants and feathers are known nest materials with such functions. The aim of our study was to experimentally assess their influence on nestlings' telomere length and attrition, which are good predictors of their survival prospects. In a full-factorial experiment, we explored these effects in two different populations, together with the potential effects of hatching date, ectoparasitism, bacterial environment and nestling growth. Telomere length and attrition largely depended on population identity and hatching date. After correcting for these effects, the addition of feathers resulted in higher rates of telomere attrition. The addition of plants did not affect nestling telomeres in general, but did in interaction with location: in Hueneja, the experimental addition of green plants resulted in longer telomeres. Feather pigmentation also did not affect telomere length or attrition in general, but did in interaction with location: in Hueneja, the experimental addition of unpigmented feathers resulted in nestlings with longer telomeres and lower attrition rates. Moreover, prevalence of staphylococci on the skin of 8-day-old nestlings was negatively related to telomere lengths of fledglings. Taken together, these results suggest a direct link between nest material composition and nestling telomere length and dynamics. This relationship could be partially mediated by the antimicrobial and/or antiparasitic properties of nest materials or by sexual signalling processes. We discuss possible roles of maternal effects, parasites, immunity and nestling growth in explaining these experimental effects., 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). J.M.P., G.T. and M.R.R. were supported respectively by Juan de la Cierva, Ramón & Cajal and Talentia postdoctoral contracts., Peer reviewed

Cancer and tumours may evolve in response to life-history trade-offs between growth and duration of development on one hand, and between growth and maintenance of immune function on the other. Here, we tested whether (i) bird species with slow developmental rates for their body size experience low incidence of tumours because slow development allows for detection of rapid proliferation of cell lineages. We also test whether (ii) species with stronger immune response during development are more efficient at detecting tumour cells and hence suffer lower incidence of tumours. Finally, we tested Peto’s paradox, that there is a positive relationship between tumour incidence and body mass. We used information on developmental rates and body mass from the literature and of tumour incidence (8468 birds) and size of the bursa of Fabricius for 7659 birds brought to a taxidermist in Denmark. We found evidence of the expected negative relationship between incidence of tumours and developmental rates and immunity after controlling for the positive association between tumour incidence and body size. These results suggest that evolution has modified the incidence of tumours in response to life history and that Peto’s paradox may be explained by covariation between body mass, developmental rates and immunity., JJS was financed by Spanish Ministerio de Economía y Competitividad (CGL2013-48193-C3-1-P) from European funds (FEDER)., Peer reviewed

Mutualistic symbioses between animals and bacteria depend on acquisition of appropriate symbionts while avoiding exploitation by non-beneficial microbes. The mode of acquisition of symbionts would determine, not only the probability of encountering but also evolutionary outcomes of mutualistic counterparts. The microbiome inhabiting the uropygial gland of the European hoopoe (Upupa epops) includes a variety of bacterial strains, some of them providing antimicrobial benefits. Here, the mode of acquisition and stability of this microbiome is analyzed by means of Automated rRNA Intergenic Spacer Analysis and two different experiments. The first experiment impeded mothers’ access to their glands, thus avoiding direct transmission of microorganisms from female to offspring secretions. The second experiment explored the stability of the microbiomes by inoculating glands with secretions from alien nests. The first experiment provoked a reduction in similarity of microbiomes of mother and nestlings. Interestingly, some bacterial strains were more often detected when females had not access to their glands, suggesting antagonistic effects among bacteria from different sources. The second experiment caused an increase in richness of the microbiome of receivers in terms of prevalence of Operational Taxonomic Units (OTUs) that reduced differences in microbiomes of donors and receivers. That occurred because OTUs that were present in donors but not in receivers incorporated to the microbiome of the latter, which provoked that cross-inoculated nestlings got similar final microbiomes that included the most prevalent OTUs. The results are therefore consistent with a central role of vertical transmission in bacterial acquisition by nestling hoopoes and support the idea that the typical composition of the hoopoe gland microbiome is reached by the incorporation of some bacteria during the nestling period. This scenario suggests the existence of a coevolved core microbiome composed by a mix of specialized vertically transmitted strains and facultative symbionts able to coexist with them. The implications of this mixed mode of transmission for the evolution of the mutualism are discussed, 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-RNM4557).
AM-G had a predoctoral grant from the Junta de Andalucía (P09-RNM-4557)., Peer reviewed

The avian nest is an essential structure for offspring development. For adults, nest building entails costs in terms of time, energy, and exposure to predators and parasites. Amount and diversity of materials used for nest building depend on their availability and functionality in scenarios of sexual selection and parasitism. Green plants and feathers of different colors have been hypothesized to play key roles in offspring protection against pathogens, and we here experimentally assessed spotless starling (Sturnus unicolor) preferences for pigmented versus unpigmented feathers and for different green plants (aromatic vs. non-aromatic plants) as nest materials. We predicted a preferential selection of unpigmented feathers and aromatic plants according to the antimicrobial properties of these materials described in the literature. We evaluated these predictions during nest building and during egg-laying stages. As expected, starlings preferentially selected unpigmented feathers both before and during egg laying, while aromatic plants were preferentially selected only during the egg-laying stage. These results suggest that starlings prefer nest materials that enhance antimicrobial protection of their offspring. We also discuss some other, non-exclusive functions that might explain the observed preference for nest materials, especially with regard to their potential role in sexual signaling, This work was supported by Spanish Ministerio de Ciencia e Innovación, European funds (FEDER) (CGL2010-19233-C03-01, CGL2010-19233-C03-03, CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P). M.R.R. received a postdoc from the program “JAE-Doc” and C.R.C. had a predoctoral grant from the Spanish Government. G.T. was supported by Ramón y Cajal program (Spain)., 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

Understanding the impressive interspecific variation in avian eggshell colouration has
attracted the attention of evolutionary ecologists for more than a century. Several functional
explanations predict positive covariation between eggshell pigmentation and
phenotypic quality of nestlings. We test this prediction in spotless starlings Sturnus
unicolor by using biometric measurements and telomere length of hatchlings and
fledglings as proxies of phenotypic quality. Female spotless starlings lay immaculate
blue-green eggs, a sexually selected signal directed to males. Pigmentation predicts
positive associations with concentration of antioxidants and testosterone in the yolk
and with paternal provisioning effort during nestling growth. Eggshell pigmentation
(blue-green chroma) is not associated with telomere length of hatchlings, which suggests
weak maternal effects on this trait. However, we find negative associations of
eggshell colouration with both body condition and telomere length of fledglings.
Moreover, we find positive associations between eggshell colouration and clutch size,
which suggests that sibling competition is higher in nests with more coloured eggshells.
Previous works demonstrated that level of sibling competition is positively related to
telomere erosion and, thus, the detected negative associations between eggshell colouration,
body condition and telomere length of fledglings would reflect higher level of
competition in nests with more coloured eggshells. We therefore speculate with the
possibility that females that lay larger clutches also lay more coloured eggshells that
elicit increased paternal provisioning effort and, thus, raise larger broods at the expense
of telomere erosion of their offspring., 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

Factors affecting the evolution of plumage conspicuousness in females are nowadays the focus of debate, and here we explore the possibility that the conspicuousness of female plumage and male participation in nest building are associated in birds. We hypothesize that males that participate in nest building will gain higher fecundity from high-quality ornamented females, whereas ornamented females will adjust fecundity to the costly nest-building behaviour of males. Large-sized species might experience higher costs of nest building and, thus, body size should affect the scenario described above. We used information on male contribution to nest construction (yes/no), male and female conspicuousness (conspicuous or cryptic plumage) and body size of Western Palaearctic passerines. In accordance with the hypothesis, we found that female conspicuousness, in interaction with body mass, was strongly associated with male participation in nest building. For large-sized species, female conspicuousness was positively associated with male participation in nest building. Discrete analyses of correlated evolution rendered evidence of female conspicuousness determining the evolution of male contributions to nest building, with the loss of female conspicuousness occurring more frequently before the loss of male participation in nest building. We discuss possible adaptive scenarios explaining the detected evidence because of mutual sexual selection in males and females, The study was financed by the Ministerio de Economía y Competitividad MINECO
(CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P, CGL2013-48193-C3-3-P and CGL2017-83103-P) and the European Regional Development Fund (FEDER), Peer reviewed

The offspring of many animals are conspicuous during parental dependence, despite juveniles generally suffering from high predation risk. However, to date, it is unclear whether offspring structural ornaments play a role in intrafamily communication. This is the case of conspicuous plumage in young birds, which is worn unchanged during a long period after fledging, when they still depend on their parents. If plumage color facilitates intrafamily interactions, its role should be more important in large-brooded species, where the strength of intrafamily conflict is potentially stronger. We therefore performed a comparative study in 210 passerine bird species to test whether an offspring structural trait, white plumage, evolves more frequently in lineages with larger clutches. We also explored the number of broods raised per year as another source of intrafamily conflict. First, we found that juvenile whiteness was more frequent in open-nesting species. Moreover, in agreement with our prediction, the presence of juvenile white tail/wing patches was strongly and positively associated with clutch size. This relationship was not due to the strong resemblance between offspring and adult plumage, which was controlled for in the statistical analyses. Moreover, the association remained significant after taking into account predation risk, for which there was information for a subset of species. In contrast, juvenile whiteness was not associated with the number of broods raised per year. These results may suggest that the evolution of juvenile conspicuousness is favored in species with potentially stronger intrabrood sibling conflict., This work was financed by the Ministerio de Economía, Industria y
Competitividad MINECO (CGL2016-79390-P, CGL2017‐83103‐P,
CGL2017-83843-C2-1-P and CGL2013-48193-C3-1-P) and the European
Regional Development Fund (FEDER)., Peer reviewed

Sexually selected signals reliably reflect individual phenotypic or genetic quality and, thus, survival prospects of holders. Telomere length is considered a good predictor of life expectancy and, consequently, exploring the links between telomere length and sexually selected traits is much needed to better understand the mechanisms that maintain the honesty of sexual signals. We manipulated the length of throat feathers in spotless starling (Sturnus unicolor) males (a sexually selected signal) before reproduction and explored its effects on telomere shortening and breeding performance in subsequent reproductive events. We did not detect an effect of the feathers clipping manipulation, but males with longer throat feathers before the experiment had shorter telomeres that also shortened more slowly than those of males with shorter throat feathers did. Moreover, length of throat feathers of males before manipulation was positively related to hatching success of second clutches. Thus, correlative but not experimental results support the expected associations between sexually selected signals, telomeres and reproduction. We discuss such results in scenarios of sexual selection where feather length reflects, but does not directly cause, telomere attrition and enhanced reproductive success. Males with longer throat feathers might be older, more experienced males (i.e., with shorter telomeres), able to buffer telomere shortening between reproductive events. Because of the absence of experimental effects, differential incubation effort of females cannot explain the detected association with hatching success, but other sexually selected traits that covary with throat-feather length could be responsible. Exploring those physiological and/or morphological characteristics related to throat-feather length should therefore be the matter of future research, This work was supported by the currently named Ministerio de Ciencia, Innovación y Universidades and European (FEDER) funds (CGL2013-48193-C3-1-P, CGL2017-83103-P, CGL2017-89063-P, CGL2015-65055-P and PGC2018-095704-B-100). MAG was financed by a predoctoral contract (BES-2014-068661) from the Spanish Ministerio de Economía y Competitividad, and GT by the Ramón y Cajal Programme., Reproductive data; Telomere data, Peer reviewed

Data file includes (i) average values of melanised (M) and non-melanised (NM) feather wear of nestling birds that grew in different nests. The file also included (ii) information of feather mass degradability of nestlings and adult birds from different nests and species estimated as the olipeptide concentration (μg x mL1) of tubes containing 4mL of PBS buffer and a colony Bacillus licheniformis D13 after 21 days of incubation at 37 ºC in constant agitation at 120 rpm in an orbital agitator (VWR, Spain). The third excel sheet contain information of bacterial loads in terms of terms of mesophilic bacteria (TSA), Enterobacteriaceae (HK), Staphylococcus (VJ), and Enterococcus (KF), and average wear of melanised (M) and non-melanised (NM) wing feathers of nestlings that grew in the same nests where bacterial loads were estimated. The last excel file contain information on feather wear of melanised and non-melanised feathers of each sampled nestlings and adult. All these data were collected the Guadix region (southern Spain) and used to perform the statistical analyses in Tables 2 and 3 in Azcárate et al. 2020 (Doi: 10.1111/jav.02320)., This work was supported by the currently named Ministerio de Ciencia, Innovación y Universidades and European (FEDER) funds (CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P, CGL2013-48193-C3-3-P, CGL2017-83103-P). MAG and SDL were financed by predoctoral contracts (BES-2014-068661, BES-2014-069116) from the Spanish Ministerio de Economía y Competitividad., Peer reviewed

Feathers are essential for avian life, and factors affecting their integrity are important to understand their evolution. These factors should depend on, among other traits, species‐specific bacterial environments and life‐history characteristics. However, interspecific variation in feather deterioration, feather susceptibility to degradation by keratinolytic bacteria (degradability), and bacterial environment, have rarely been quantified. Here, we did so by measuring deterioration and degradability of wing feathers of fledglings in 16 bird species, and characterizing the bacterial environment where they developed. We found statistically significant interspecific variation for all considered variables. On average, non‐melanised were more deteriorated than melanised feathers, but differences depended on the species. Moreover, nest bacterial loads were related to feathers wear, but the sign of the association depended on the bacterial group considered and on feather pigmentation. We also found a positive association of feather degradability with wear of non‐melanised feathers, and with bacterial loads. These results suggest that bacterial environments determine the integrity of fledgling feathers as well as their resistance to bacterial degradation, which implies a preponderant role of bacteria in driving the evolution of avian feathers., This work was supported by the currently named Ministerio de Ciencia, Innovación y Universidades and European (FEDER) funds (CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P, CGL2013-48193-C3-3-P, CGL2017-83103-P). MAG and SDL were financed by predoctoral contracts (BES-2014-068661, BES-2014-069116) from the Spanish Ministerio de Economía y Competitividad., Peer reviewed

Study area and study species
The study was conducted during the years 2015, 2016 and 2017 in a south-eastern
region of Spain (Hoya de Guadix, 37º15’N, 3º01’W), where nest-boxes attached to tree
trunks or walls at 3–4 m above-ground are available for starlings to breed in (for further information on the study area see Soler et al. (2017)).
In the studied starling population, the reproductive season starts in early April and
most individuals lay a second clutch during May-June. The most common clutch size is
62 plants to the nest, which have been shown to have antimicrobial-beneficial functions4-5 eggs. Here, we will focus on the colouration of the base of the beak, a trait with a more marked sexual differentiation as we can see in its reflectance at different wavelengths (Fig. 1).
Fieldwork and experimental procedure In this population, courtship activity (e.g. singing, introducing fresh green plants and feathers in nest boxes) starts in February, more than one month before egg laying (pers. obs.). During this period, some birds roost in nest-boxes and we take advantage ofthis fact for conducting yearly bird trapping sessions in the study area (twice a year between February and mid-March). One hour before dawn, we closed the entrance of all nest boxes in the study area, and immediately after dawn, we captured by hand all individuals found roosting inside. Captured birds were kept individually in clean cotton bags hanging from a stick to keep birds quiet, and were released immediately after sampling. The maximum time that a captured starling was in the bag did never exced three hours. We explored the possible effect of time that birds were kept in the bag on bird colouration and body condition measures of the males that we recaptured by classifying them as being kept in the bag less than 1 hour (N(males) = 10), between 1 and 2 hours (N = 5), and between 2 and 3 hours (N = 7). After controlling for the effect of date of first and last capture, time between captures, treatment and size of throat feathers in the first capture, results showed that retaining time 184 in first captures did not significantly affect blue, red-yellow, or brightness colouration of the beak of males (F1,15 < 2.66, P > 0.124), nor body condition (F1, 10 = 2.19, P = 0.170) in subsequent captures. It neither had any apparent long-term consequences (see Ruiz-Rodríguez et al. (2015)), nor imply apparent negative effects on breeding performance of captured birds (Soler et al. 2008), This work was supported by the currently named Ministerio de Ciencia,es and European (FEDER) funds (GL2013C-48193-C3-1-P, CGL2017-83103-P Innovación Universidad, CGL2017-89063-P). MAG was financed by a predoctoral contract (BES-2014-068661) from the Spanish Ministerio de Economía y Competitividad, and GT by the Ramón y Cajal Programme, Peer reviewed

Avian brood parasites are expected to select host nests according to characteristics that maximize offspring fitness, such as reduced probability of ectoparasitism. Spotless starlings, Sturnus unicolor, lay immaculate blue eggs that sometimes become brownish-spotted due to the activity of the ectoparasitic fly Carnus hemapterus on incubating birds. Therefore, conspecific parasitic females should adaptively avoid parasitizing nests with spotted eggshells. Here, we manipulated perceived risk of ectoparasitism by painting the eggs with either brown spots (similar to those due to ectoparasite activity) or blue spots. A third group of nests was maintained with immaculate eggshells. Nests with nonspotted eggshells showed the highest rate of brood parasitism, while nests with brownish or bluish spots on the eggshells were parasitized at a similar lower rate. These results suggest that brood-parasitic females use the presence of spots on the eggshells in their selection of host nests. This study adds to the scarce evidence showing that brood-parasitic birds select host nests with a low risk of ectoparasitism and demonstrates that colour patterns of the eggshell (i.e. spottiness) of their potential hosts represent a major cue employed to appraise the risk of ectoparasitism., This work was supported by the currently named Ministerio de Ciencia, Innovación y Universidades and European (FEDER) funds (CGL 2013-48193-C3-1-P, CGL 2017-83103-P, CGL 2017-89063-P). M.A.G. was financed by a predoctoral contract (BES-2014-068661) from the Spanish Ministerio de Economía y Competitividad, and G.T.y the Ramón y Cajal Programme., Peer reviewed