Thesis (Ph.D.) - University of St Andrews, April 2009.

Quantifying the pattern and magnitude of spatio-temporal variation in demography, and identifying underlying causes, is key to understanding population dynamics. Using long-term, spatially-explicit data from a small population of European Starlings (Sturnus vulgaris) on Fair Isle, Scotland, I quantified spatio-temporal variation in demography and investigated its underlying mechanisms. I objectively described the population’s physical structure and hence defined spatial clusters of nest sites at multiple spatial scales. I quantified spatio-temporal variation in reproductive success and survival, across clusters and years. I explicitly included multiple broods in these analyses, examining their effects on variation in reproductive success and pre-breeding survival. My results demonstrate substantial small-scale spatial variation in both reproductive success and adult survival, contesting the common assumption that demography will be spatially homogeneous at small scales within populations that lack obvious subdivision. The inclusion of second broods had a substantial effect on spatio-temporal variation in reproductive success, however, the pre-breeding survival of second-brood individuals was so low that ultimately they may not have a large effect on population dynamics. I quantified dispersal movements of colour-ringed individuals, demonstrating that individuals breed significantly closer to their natal site than expected under random settlement. Individuals that left their natal cluster to breed moved to less productive clusters more than expected, and the difference in productivity between natal and breeding clusters did not vary with the number of available nest sites in the breeding year. The absence of nest-site availability effect suggests such patterns are consistent with source-sink dynamics, rather than site-dependent population regulation. Finally, I quantified the effect of grassland availability on demographic variation, since reduction in grassland is postulated to be a major factor in starling decline across Europe. However, there was no significant effect of the proportion of grassland surrounding the nest site on reproductive success or subsequent survival.

No description available.

Variation in morphology and genotype among individuals of the same species occurs almost everywhere in the natural world. Such variation underlies natural selection and any resulting evolution, and therefore needs to be quantified in order to predict and understand phenotypic and evolutionary dynamics. Where morphology or genotype vary non-randomly in space, structured spatial variation can arise. Such spatial variation can arise from, and cause, further evolutionary processes including local adaptation and speciation. Here, I quantify spatial variation in neutral genetics and morphology, and in selection on morphology, occurring at a very small spatial scale within a single population of European starlings (Sturnus vulgaris) resident to the Island of Fair Isle. I demonstrate weak but statistically significant genetic structure in microsatellite loci by FST comparison but that similar structure is not supported by Bayesian cluster analysis. I also show significant genetic structure between populations of starlings within the UK from England, Scotland, Colonsay, Orkney and Shetland, and show that there are two main genetic clusters supported by Bayesian cluster analysis. I show there are significant differences in weight, tarsus lengths, bill lengths, bill size and, body condition among three, spatially proximate, spatial areas within Fair Isle thereby demonstrating significant small-scale spatial variation in morphology within this island population Using capture mark recapture analysis to estimate survival probabilities I evidence the occurrence of stabilizing selection on weight and disruptive selection on tarsus length in starlings but find no evidence that selection on morphology differed between sexes or among areas within Fair Isle. I conclude that small scale spatial variation in morphology and neutral genetics can occur on small spatial scales even in species with high potential mobility and where there are no distinct differences in environment and movement is not physically inhibited.

No description available.

The function of the complex song of the European Starling (Sturnus vulgaris) was examined. Song playback experiments showed that both male and female starlings were attracted by song, and complex song inhibited males from entering nestboxes. Wild starlings (at least two years old when first recorded) showed extensive changes in the composition of their song phrase repertoires and most also increased the size of their repertoires, which will result in a correlation between age and repertoire size in this species. Females prefer males that have more complex song, and this preference remained significant when preferences for certain nest sites were controlled. Males with larger repertoires did not spend more time incubating or make more feeding visits to nestlings than did males with smaller repertoires. The evolution of complex song in the European starling is consistent with an age-indicator model of sexual selection, in which aspects of male quality correlated with age are advertised by the complexity of male song.

Invasive species are problematic but their control can be difficult. When the history and dynamics of invasive populations are unknown, analytical techniques utilising genetic data can provide information to management. The application of these techniques has typically been limited to species with restricted dispersal or to localised geographic scales. Here these techniques are used in conjunction with traditional approaches to study the invasion of a highly vagile species over a continental scale. Originally introduced to eastern Australia, the common starling (Sturnus vulgaris) is expanding westward and has reached the southeast agricultural region of Western Australia (WA). Spatial, temporal and museum samples representing historical incursions into WA were used in genetic analyses to answer questions important to WA management agencies. Where possible, multiple marker classes were used to evaluate their relative ability to address these questions, including microsatellites, mitochondrial DNA (mtDNA), and a nuclear gene. Between two and four genetic groups were identified in Australia, and the localities on the edge of the range expansion (ERE) were consistently genetically differentiated from all others. Levels of genetic exchange between groups appeared to be low, suggesting that localised control may be effective. Analyses of historical samples indicated patterns of genetic exchange are temporally stable. This suggests that starlings will continue to arrive from the east, requiring vigilance from management. Consistently, a negative relationship was found between genetic diversity and date of first record, which may help in the future to distinguish ineffective surveillance from recent colonisations. Genetic evidence of female-biased dispersal indicated that control strategies preferentially targeting females may more efficiently limit dispersal than those targeting both sexes equally. Variants private to particular genetic groups were identified; tracking the spread of these variants may assist future monitoring programs in understanding ongoing exchange between groups. One mtDNA variant private to ERE localities showed dramatic temporal change, which could not be adequately explained by genetic drift or admixture, but may be explained by selection. Microsatellites were most useful in determining origins and identifying dispersers, mtDNA sequences provided a unique tool for ongoing monitoring of dispersal, and nuclear sequences had high levels of gene diversity and resolution of population structure.

El Estornino Pinto (Sturnus vulgaris) es un ave nativa de Europa, Oeste de Asia y norte de África que ha sido introducida en numerosos países y actualmente es considerada una de las 100 especies más invasoras del mundo. En la Argentina fue introducida en la década del 80 y a partir de ese momento se ha observado un aumento importante en la cantidad de ejemplares por bandada y una expansión a distintas provincias del país. Entre noviembre de 2010 y octubre de 2011 se realizó un censo de aves en el parque Pereyra Iraola y una búsqueda de nidos de estorninos y de otras especies. Se determinó que actualmente el Estornino Pinto es la especie que nidifica en cavidades con mayor densidad en la zona (1,47 individuos/ha). Para nidificar utilizaron una gran variedad de cavidades, principalmente en árboles vivos pero también en árboles muertos y construcciones humanas como techos de viviendas y luminarias. Se observaron interacciones agresivas con dos parejas de carpinteros y con un hornero por el uso de estas cavidades. En estos casos el estornino no logró desplazar a las otras aves, pero por otro lado se registraron dos parejas de estornino nidificando en cavidades que unos días antes estaban siendo construidas carpinteros. Durante cuatro temporadas reproductivas (septiembre-diciembre de 2010, 2011, 2012 y 2013) se realizó un estudio de la biología reproductiva del estornino mediante el uso de cajasnido. El Estornino Pinto fue la única especie que las utilizó. Dentro de las cajas construyeron un nido voluminoso utilizando principalmente gramíneas y ramas. También utilizaron hojas verdes, hojas secas, corteza, líquenes, clavel del aire, vainas de leguminosas, flores, crines y estiércol de caballo, bolitas de barro y materiales artificiales. El tamaño de la puesta fue de 4,06 ± 0,13 huevos por nido y el éxito de eclosión del 77,5%. Nacieron en promedio 3,15 pichones por nido y se produjo reducción de nidada en el 37,9%. En el 67% de los nidos donde nacieron pichones la totalidad de ellos murieron. La proporción de pichones que sobrevivieron por nido fue muy baja (x= 0,24) y disminuyó en las nidadas tardías, viendose afectada negativamente por la temperatura ambiental, mientras que las precipitaciones tuvieron un efecto positivo sobre la supervivencia de los pichones. La temperatura ambiental también tuvo un efecto subletal sobre los pichones, disminuyendo el peso asintótico alcanzado conforme aumentó la temperatura. Los pichones fueron parasitados por larvas de Philornis mostrando la prevalencia más alta (61,82%) registrada en aves de Argentina y con una intensidad media de 10,7 larvas por pichón. En el 60,7% de los nidos con pichones parasitados no sobrevivió ningún pichón. La proporción de pichones que sobrevivieron por nido varió en función de la edad a la que fueron parasitados, siendo menor cuando el parasitismo ocurrió a una edad más temprana, sin embargo, no se vió afectada por la intensidad de Philornis. Se analizó el contenido estomacal de pichones y se observó que consumieron principalmente larvas y adultos de coleópteros, himenópteros y larvas de lepidópteros. En menor proporción consumieron alimento vegetal, encontrándose semillas de Morera Negra Morus nigra en el 48,7% de los estómagos, por lo que el estornino podría estar actuando como un dispersor de especies vegetales exóticas. También se encontraron piedras en el 53% de los estómagos. La proporción de artrópodos disminuyó y la de alimento vegetal y piedras aumentaron con el crecimiento de los pichones y al avanzar la temporada reproductiva. Con respecto a los parásitos, se encontraron ooquistes de Isospora sp. (Coccidia) con una prevalencia del 26,8% en muestras de heces de pichones y huevos de cestode sólo en una muestra. También se extrajeron los ectoparásitos de pichones y juveniles de estornino muertos y de pichones vivos, encontrando sólo ácaros de la especie Ornithonyssus bursa. Todas estas especies son cosmopolitas y se encontraban previamente en la zona, por lo que el estornino no habría adquirido nuevas especies de parásitos, con excepción de Philornis, ni habría transmitido nuevos parásitos a las aves nativas Esta tesis constituye el primer estudio sobre los distintos aspectos de la invasión del Estornino Pinto en la Argentina y aporta datos importantes para el conocimiento de la situación de esta especie en el Noreste de la provincia de Buenos Aires que podrían utilizarse en un futuro con el fin de implementar estrategias de control de la especie.

Selection operates when the variability among individuals in heritable traits translates to differences in the number of offspring that survive to breed, which is a close estimate of fitness. Consequently, the outcome of sexual-selection should be higher reproductive success for individuals with a greater expression of the selected traits. In this thesis, the relationship between some male spotless starling (Sturnus unicolor) traits and reproductive success was assessed. A particular focus was given to the role of throat feathers (TF) as sexually selected trait. The study was conducted in a wild population using a correlative approach in 2004, while in 2005 and 2006 the TF of males were experimentally shortened. The genetic parentage of the offspring was required for determining the reproductive success of males. Nine highly polymorphic microsatellites (with 11.7± 3.2 alleles per locus) were developed and optimised for this species. Parentage analyses were conducted in NEWPAT XL and CERVUS 3.0.3 and confirmed using observational data. Eighty-five percent of the offspring had at least one parent assigned. The levels of intra-specific brood parasitism, extra-pair paternity and quasi-parasitism were 7%, 7% and 1% of the offspring, respectively. Polygamy levels decreased with year, as the study population matured. The correlative study showed that males with longer TF and with better condition had a higher probability of reproducing and sired more offspring, but their offspring were not of higher quality as measured by their weight and immune response to phytohaemagglutinin. Polygynous males were also in better condition. In the experimental study, males in better condition had a higher chance of reproducing and sired more fledglings. Conversely, males with reduced TF sired significantly fewer eggs and lighter fledglings than control males. Body condition and TF length are shown to be good predictors of reproductive success and TF length is shown to be under sexual selection.

This research was performed to determine; (1) the prevalence of Toxoplasma antibodies among starlings in Northern California, (2) if such starlings can transmit the disease, and (3) if tissues from seropositive starlings contain encysted forms of T. gondii.