Dynamics of avian pathogens

The emergence of new diseases and re-emergence off old ones is an important component of global change. Many of these emerging infectious diseases are zoonosis and have its main reservoirs in birds. We focus on three different pathogens: West Nile virus, avian influenza and avian malaria. Besides the risk supposed by some of these pathogens to human health, pathogens can play an important role in the regulation of wild birds populations, and have important effects on host ecology and life-history strategies. We have identified ecological factors related to interspecific differences in the exposure to West Nile virus, avian haematozoa and some other parasite groups in the wild, that may help to set-up i.e. West Nile virus monitoring programs in the field.

Our current research aims to determine the factors related to West Nile virus circulation in Spain. For this we are focussing on the prevalence of antibodies in birds, virus in mosquitos, and changes in mosquitos feeding preferences. We are also monitoring the circulation of low pathogenicity influenza in wild birds to understand the factors related to changes in virus prevalence and the potential impacts of infection of animals health. For this we are monitoring the transmission rates of the different pathogens to determine the environmental, ecological and genetic factors related to the transmission rates in the populations and risk and impact of infection at the individual level.

Dispersal in aquatic systems

Freshwater ecosystems can be viewed as islands of water surrounded and isolated by a sea of land. How can non-flying organisms living in these systems colonize and disperse between wetlands? Waterbirds were proposed as the vectors of dispersal, but little quantitative evidence was available in the field. Our research has focussed on the role of waterfowl in the local and long-distance dispersal of aquatic organisms. We have demonstrated that waterbirds disperse plants and invertebrates at a local scale, but that local adaptation can limit the capacity for long-distance dispersal into already established populations. Currently I am interested in the role of waterbirds in the spread of invasive species, virus and on the role of local adaptation and priority effects in limiting the capacity for successful dispersal. Our current work combines the use of molecular techniques, field observations and information on the movements of birds to determine the impact of bird movements on the population structure of autochthonous and invasive Artemia. We are also building models based on bird movements to understand the patterns of long distance transport of invertebrate eggs and plant seeds by waterbirds.

Sexual selection and the evolution of sexual size dimorphism

Sexes in many species differ in size and coloration. These differences are supposed to have evolved by sexual selection, but why males are larger than females in some birds, and the reverse occurs in others? Species also differ in the degree of dichromatism, males are brighter in some cases, but in others both males and females present the same drab or ornamented plumage. I am interested in how birds ecology is related to sexual differences in size and coloration.

Most of my research has focussed in the role of sexual displays and mating system in explaining the female-biased dimorphism that predominates in shorebirds and raptors, but my current research focus on the relationship between the expression of ornaments and natural selection. I'm also interested in the interaction between size and colour dimorphism, and the possible ecological factors affecting its evolution. At the intraspecific level I have attempted to test the role of coloration as indicator of parasite load and health status using both correlational analyses and the experimental manipulation of parasite loads before molt and the measurement of plumage coloration after molt. For example, we eliminated the ectoparasites of male serins (Serinus serinus) before molt, and measured the colour characteristics of the new plumage. Insecticide treated birds (black bars) developed a brighter plumage than untreated birds (white bars), suggesting that ectoparasites had a negative effect on the development of bright plumages.

Population dynamics and conservation

Habitat loss and fragmentation is a widespread phenomena around the world. Many populations are exposed to the alteration of their habitats and populations of many species are declining. Due to the extend of habitat transformations in Europe, the conservation of many species is closely linked to the maintenance of environmental friendly agriculture practices. I am interested in the influence of rice-fields on the population dynamics of waterbirds. My research focus on the potential benefits but also the potential risk for animals using rice-fields as alternative habitats. I am also involved in the monitoring of two bird species with completely different situations.

In 1994 I started the monitoring of a small Kentish Plover (Charadrius alexandrinus) population breeding in the Llobregat Delta, a natural area very close to Barcelona. In collaboration with Paco Cerda, Tomas Montalvo and Quim Bach we have studied this population since then. In the first years our research focussed in the identification of the factors affecting negatively this population. From 2001 onwards, a major reclamation operation affected the breeding habitat of 40% of the population, and we had an unvoluntary experiment on the effects of habitat loss. How a natural population respond to this habitat loss is our main current interest. Our research goes beside estimating the impact on global population, we aim to analyze how birds behaviour affect the redistribution and nesting decisions (stay or emigrate) of individuals.

The second study organisms is exposed to a completely different situation. The Glossy Ibis (Plegadis falcinellus) got extinct from Doñana during the XIX century. After several failures, a new breeding population established in Doñana in 1996. In less than 9 years this population has growth up to ca. 1000 breeding pairs in 2004. A significant number of the chicks have been marked with white tags with three digits in black that can be easily read from a distance with telescope. We aim to estimate the dependence of Doñana population from self-recruitment and immigration from other colonies. We are investigating use of the habitat by the species and the possible competence (if any) with the different species of herons breeding in the area. The Glossy Ibis present a very important sexual size dimorphism (sexes do not overlap in tarsus size), so this is an ideal system to assess the effects of size dimorphism on habitat use and birds ecology.

Evolution and maintenance of color polymorphism

We are interested in the evolution, maintenance and adaptive function of alternative behavioral, physiological and life history strategies that coexist in a given population. We approached this by taking advantage of a widespread phenomenon in natural populations; i.e. the genetic color polymorphism. Color polymorphism is defined as the presence of two or more distinct, genetically determined color morphs within a single interbreeding population, the rarest of which is too frequent to be solely the result of recurrent mutation.

Our study species is the Eleonora's falcon (Falco eleonorae). This is a colonial long-distance migratory raptor species that exhibits a striking melanin-based color polymorphism with individuals displaying a pale or dark morph that is inherited in a simple Mendelian way.

We demonstrated that variation of plumage coloration in this species is due to the presence of alternative alleles at the MC1R gene. But, is genetic color polymorphism associated to other life-history traits? We demonstrated the existence of covariations between plumage polymorphism and physiology (response to oxidative stress and immunity) and also breeding performance.

What are the long-term ecological and evolutionary consequences of displaying alternative plumage colorations?
Our current work uses a multidisciplinary approach that combines molecular and biochemical techniques, field observation and experiments, and high resolution monitoring (tracking) systems to answer this question in a collaborative working framework.