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En la presente tesis se investigan las restricciones energéticas que experimentan las aves nidicolas y como estas limitaciones pueden afectar a la determinación del tamaño de puesta. Se analiza el efecto que tiene el hábitat, las condiciones metereologicas y la disponibilidad de alimento sobre el esfuerzo de la hembra en los periodos de la incubación y de la ceba de los pollos, mediante la comparación de dos poblaciones, una en un área marginal y otra en uno mas optimo. Se estima la importancia que tiene el coste de la incubación a la hora de afectar a la determinación del tamaño de puesta. Se relaciona el coste energético que supone a una pareja la cría de los pollos, con las modificaciones del esfuerzo parental al cambiar el tamaño de nidada. Se discrimina entre las hipótesis que se han propuesto para la determinación del tamaño de puesta en las aves nidicolas. Por ultimo, se esclarece a que se debe la perdida de peso en las hembras de las aves nidicolas después de la eclosión de los pollos, separando entre las dos hipótesis propuestas hasta el momento. Para realizar la investigación se ha trabajado con el papamoscas cerrojillo, un ave insectívora forestal que utiliza las cajas nido con frecuencia

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Esta tesis fue leída el 14 de junio de 2021 en la Universidad de Valencia y forma parte del Doctoral Program in Biodiversity and Evolutionary Biology (RD 99/2011) del Departamento de Zoología de la Facultad de Ciencias Biológicas de dicha universidad.-168 pp., Avian incubation is a complex behaviour that, in female-only incubator species, entails key trade-offs between egg warming periods and time off the nest for female self-maintenance. The dynamics between on- and off-bouts are thought to be mainly influenced by ambient temperature, because changes in egg cooling rates would influence how females allocate their time during the incubation period. Incubating females need to keep an adequate and narrow thermal environment for the egg, with small deviations causing long-term effects on survival and reproductive success. Females would need to adjust their bout duration to ambient temperatures. Both on- and off-bouts are expected to lengthen when temperatures increase because incubation constraints are eased. Females usually lengthen on-bouts at a higher rate, thus increasing incubation effort. The opposite response, i.e., increasing self-maintenance time with increasing ambient temperature, has been also reported in both different species and different populations of the same species. While these opposite behavioural responses might be the result of different breeding strategies adapted to habitat conditions, it might also be that they arise as artefacts of limited datasets, different methodological approaches, or the timescale at which incubation behaviour is measured. Determining the onset of incubation also implies certain complexities derived from trying to delimit a progressive behaviour that is gradually settled during the egg-laying period. Despite classic studies, performed forty years ago in Great Tits Parus major describing both diurnal and nocturnal incubation behaviours and their respective periods of partial and full incubation, little is known about how the onset of incubation relates to ambient temperature and its effects on hatching asynchrony. Ambient temperature might have a major role in the onset of incubation if incubating females use it as a cue to synchronize their hatchlings maximum growth period with the expected prey peak. Prey development, mainly caterpillars for Great Tits, accelerates with increasing temperatures. Once females start laying eggs, they could only keep track of faster prey development by an earlier onset of incubation. But an earlier onset also implies that incubation happens before the clutch is complete, which could cause hatching asynchrony. Hatching asynchrony could still occur even if incubation is delayed after clutch completion. Thermal gradients within the clutch during incubation might be a potential factor behind this residual hatching asynchrony. Females keep eggs under their brood patch warmer than peripheral ones, because they are not able to cover the whole clutch. If females do not distribute the heat properly by repositioning eggs within the nest-cup it could cause a differential embryo development, potentially resulting in hatching asynchrony., In this thesis project I have chosen a commonly studied species, the Great Tit, and collected high-quality incubation data during three consecutive years in three different breeding populations. The main aim of the project was a better understanding of the dynamics of incubation behaviour, its onset, and the consequences on hatching asynchrony in relation to ambient temperature. During an additional fourth breeding season, I also investigated whether differential egg repositioning within the clutch, a rarely studied behaviour, had a role in hatching asynchrony. Incubation behaviour was recorded using temperature data loggers placed in the nest-cup and egg repositioning was calculated from photographed clutches during the incubation period. First, I delimited the different incubation behaviours (diurnal and nocturnal, and partial and full incubation), quantified them, and assessed how ambient temperature affected their onset relative to the egg-laying sequence. I also assessed the association between the onset and duration of these incubation behaviours and the extent of hatching asynchrony. Secondly, I tried to comprehend incubation rhythms (i.e., the relation between on- and off- bouts during diurnal full incubation), their number and duration, in relation to ambient temperature. I aimed to investigate whether divergent patterns of nest attentiveness were a result of local adaptations or the consequence of incomplete datasets and different analysed timescales (hourly, daily, overall incubation period). Finally, by using an experimental approach, I deterred clutches from being partially incubated and assessed the effect on hatching asynchrony. I also investigated if residual hatching asynchrony could be endorsed to differential egg repositioning within the clutch by taking twice-a-day photographs of marked eggs during the diurnal full incubation period. The duration of the diurnal full incubation was analysed under the effect of different factors related to each objective. I found that both ambient temperature and clutch size affected the onset of incubation behaviour (Chapter 1). Increasing ambient temperature during the egg-laying period advanced diurnal partial incubation relative to the laying sequence, but larger clutches delayed the onset of both nocturnal full incubation and diurnal partial incubation. Only diurnal incubation affected hatching asynchrony despite nocturnal periods being longer. Both partial incubation and full incubation occurring before clutch completion increased hatching asynchrony. In Chapter 2 I showed that incubating females allocated time into self-maintenance at higher ambient temperatures, i.e., reducing nest attentiveness when constraints alleviate, as a generalized response among populations. Females maximised the duration of incubation bouts based on local temperatures and not absolute values as suggested in previous studies. This behaviour translated into different nest attentiveness patterns depending on the timescale, even showing contrary incubating behaviours.Going beyond correlational studies, in Chapter 3 clutches where partial incubation was prevented showed longer incubation periods and reduced hatching asynchrony. However, egg repositioning within the clutch did not seem to be the cause behind the observed residual hatching asynchrony. Ambient temperature is a key variable for incubation behaviour, both for its onset and rhythms. It affects the onset of incubation asymmetrically, advancing only diurnal partial incubation. Female incubation rhythms differ among populations because they maximise onbout duration at different local ambient temperatures. Ambient temperature, both during the egg-laying and full incubation period, is indirectly associated with the duration of the full incubation period and the extent of hatching asynchrony., This project would have not existed without the funding granted by former Spanish Ministry of Economy and Competitiveness (MINECO) (CGL2013-48001-C2-1-P and CGL2016- 79568-C3-1-P) thanks to the European funds “Fondo Social Europeo” (FSE). To work on this project, I was supported by an FPI fellowship (BES-2014-069191, MINECO and FSE) and two short-term research stays in North Carolina Museum of Natural Sciences (Raleigh, NC, USA) (grant EEBB-I-16-11668, MINECO), supervised by Dr Caren Cooper; and in the FitzPatrick Institute of African Ornithology (Cape Town, South Africa) (grant EEBB-I-18-12903, MINECO), supervised by Dr Susan J. Cunningham, who greatly contributed to achieve my objectives.

The study of the factors that determine the structure and genetic diversity of natural populations is critical to understand their demographic and evolutionary trajectories and thus to predict their responses to future environmental changes (Freedman et al. 2010). In this thesis we have studied the genetic structure and the relationship between genetic diversity and fitness measured in terms of parasite prevalence, survival and development of ornaments in Mediterranean populations of blue tits (Cyanistes caeruleus). We used microsatellite markers classified as neutral and functional depending on whether they are located in regions of the genome that are actively transcribed RNA (Olano-Marín et al. 2011ab). The results of the genetic analysis showed some limitation to gene flow between the populations studied. The females had higher dispersion distances than males, a pattern that was reflected in the presence of genetic structure in males but not in females. Landscape genetic analyzes also revealed a genetic structure of populations, although it was subtle, possibly due to habitat fragmentation could force individuals to disperse greater distances through unfavorable habitats to reach new breeding sites (Wiens 2001; Harrison et al. 2013). Furthermore, the genetic structure was detected primarily to neutral markers, which could be because the functional markers were subject to selection stabilizer. The spatial heterogeneity and fragmentation of populations also seem to have generated differences in the prevalence of avian malaria between areas of study. The probability of infection with avian malaria was non-linear associated with heterozygosity estimated with neutral markers, so that individuals with intermediate levels of heterozygosity had higher probability of being parasitized (Blondel et al. 2009; Ruíz-López et al. 2012). This relationship was not significant for subset of functional markers, not differ between study areas with different degrees of parasitic pressure. However, the environmental context influence on direction and intensity of the relationship between genetic diversity and annual probability of survival. In particular, we observed that accumulated precipitation was positively correlated with the intensity of selection on heterozygosity. In addition, the selection of heterozygous individuals and moderate heritability of heterozygosity seem to have generated a gradual increase of genetic diversity in the population, suggesting a micro-evolutionary response to selection (Kaeuffer et al. 2007; Forcada & Hoffman2014). Finally, we observed a positive relationship between the expression of secondary sexual characters and heterozygosity estimated with functional markers on males. This indicates that the mechanism by which females select partner might be mediated by the increased capacity of males with high genetic diversity to develop ornaments, which could facilitate the election by the female of a couple with higher genetic quality (Candolín 2003). Overall, the results from this thesis highlights the importance of integrating different types of molecular markers and ecological data obtained at different space-time scales to improve understanding of the factors that determine the genetic structure of natural populations, as well as the consequences that genetic diversity has on different components of fitness.

The spatial and temporal variability of migratory phenology of Ciconia ciconia, Cuculus canorus, Apus apus, Hirundo rustica and Luscinia megarhynchos were studied by means of 44000 records for 1400 spanish sites during the period 1944-2004. In all species, first individuals arrive to the southern areas of Iberia, to low altitude sites, with dry and warm summers, and near to the Straits of Gibraltar. A. apus and H. rustica showed quite similar spatial patters due to the strong influence of fixed factors, which impose optimum migratory pathways. The onset of singing of C. canorus and L. megarhynchos showed a different and weak geographical pattern, which suggests that other local environmental factors could be influencing singing behaviour of males. In spite to be a soaring species, C. ciconia follows similar spatial patters for spring arrivals. However, its autumn departure and length of stay did not show any spatial gradient. Excepting L. megarhynchos, all species have advanced their arrival dates during the last three decades. Nevertheless, current dates are similar to those recorded sixty years ago. The strongest advancement was detected in C. ciconia, probably as a result of the growing number of wintering individuals in Iberia. In overall, species arrived earlier those years with plentiful rainfalls in western Africa and warmer spring temperatures in Iberia. Therefore, climate change is probably the underlying mechanism for temporal changes in migratory phenology also in Mediterranean populations. Departure dates only showed a significant advancement in H. rustica. Departures were weakly related to climatic variables. Temperatures during breeding period advanced departures in all species, while only H. rustica was affected by temperatures at departure time., S'estudià la variabilitat espacial i temporal en la fenologia de la migració de diverses aus trans-Saharianes. Es van fer servir unes 44000 dates d'arribada i emigració de cigonya ("Ciconia ciconia"), cucut ("Cuculus canorus"), falciot ("Apus apus"), oreneta ("Hirundo rustica") i rossinyol ("Luscinia megarhynchos") enregistrades a unes 1400 localitats espanyoles entre 1944 i 2004 pels voluntaris de la xarxa fenològica de l'"Instituto Nacional de Meteorologí"a.Totes les espècies colonitzen la Península Ibèrica seguint un eix sudoest-nordest durant la primavera. Els primers individus arriben al sud, a localitats a baixa altitud, amb estius secs i calorosos i properes a l'Estret de Gibraltar. En el cas de l'oreneta i el falciot els patrons van ser especialment similars degut a la dependència de factors ambientals invariables, com ara el relleu, que marquen les rutes migratòries òptimes a través de la península en ambdues espècies. L'inici del cant va mostrar patrons espacials diferents en el cucut i el rossinyol, probablement com a resultat de la biologia tan diferent d'ambdues espècies. L'escassa capacitat predictiva dels seus models podria indicar que el cant també depèn d'altres factors que incideixen sobre les decisions dels mascles de cantar o no fer-ho i que són alienes a la migració. L'arribada de la cigonya segueix els patrons generals citats anteriorment tot i ser una espècie planadora. Pel contrari, les diferències entre localitats en les dates d'emigració i la durada de l'estada no tenen cap estructura espacial en aquesta espècie. Les cigonyes es reuneixen en grans estols durant la migració post-nupcial que tenen un comportament independent de les condicions ambientals de les localitats on crien. L'estada depèn més de la data quan els individus decideixen marxar, que de la data quan arriben.La cigonya, cucut, falciot i oreneta han avançat la seva data d'arribada durant els darrers trenta anys, tot i que les dates enregistrades a l'actualitat són semblants a les que s'enregistraven ara fa seixanta anys. L'excepció és la cigonya, que sí ha avançat l'arribada en torn un mes. Aquest canvi tan brusc probablement està relacionat amb el nombre cada cop més gran d'individus que roman a la península durant l'hivern. Aquesta tendència a no migrar possiblement és el resultat combinat dels costos d' anar a les àrees clàssiques d'hivernada del Sahel, on les sequeres persistents provocarien una elevada mortalitat entre els individus que hi van, en comparació amb els beneficis de romandre tot l'any a la península, on la proliferació de deixalleries i certes espècies invasores proporcionen una font contínua d'aliment que abans no existia. L'arribada es va veure afectada tant pel clima de les àrees d'hivernada com el de cria en la resta d'espècies. Les aus arriben abans els anys humits a l'Àfrica occidental i les primaveres càlides a la península. Els canvis climàtics de les darreres dècades són, doncs, els responsables més probables dels canvis temporals en les dates d'arribada. Les dates d'emigració de la cigonya, falciot i oreneta van mostrar fluctuacions temporals similars, avançant la seva sortida fins a mitjans dels 60, ajornant-la fins a mitjans dels 80 i tornant-la a avançar d'ençà les hores. Temperatures elevades durant l'època de reproducció es van associar amb un avançament de l'emigració a les tres espècies, mentre que només l'oreneta es va veure afectada per les temperatures durant el període d'emigració, anant-se més tard aquells anys més calorosos durant aquestes dates. Podem concloure que les xarxes de voluntaris constitueixen una bona eina per avaluar la variabilitat espacial escala i temporal de la migració de les aus i que s'haurien de seguir potenciant, especialment ara, donada la sensibilitat de la fenologia al canvi climàtic.