Vicente Polo

Circadian routines and fattening strategies in small birds. To survive the winter conditions, which are changing and restrictive in highly seasonal environments, birds depend on their internal level of fat reserves. Because of this, natural selection has given priority to the appearance of physiological and ethological processes of fine-tuning of these internal levels. An experimental design investigated the causal agents that affect fattening strategies, such as temperature, light hours, level of dominance within the flock, quantity and predictability of food access, risk of predation and the costs of flight. Fieldwork has been carried out in two countries (Spain and Scotland). The works have led to a different model that fits the shape of the circadian routines of body weight.
Distribution and abundance of bird species by body size.- Birds, in general, can exploit three-dimensional environments . However, abundances are measured on the projected surface of the terrain. Due to this discrepancy, there are no good adjustments in the distribution of species by body size in this group of animals (and in others, like many arthropods, which may also live in very complex environments). I have analyzed the ecological and evolutionary components of 277 nesting passerines in the Western Palearctic of body weight as well as their habitat preferences and use of space while searching for food. The results showed that the evolution has not produced a neutral variation in size, in the sense that the highly complex means have favored the appearance of light species, able to exploit the fine structural segments of the same, whereas it does not appear to have hampered the settlement of large birds.
Sexual selection and systems of honest signaling in the black starling: role of testosterone in females.- Sexual selection is a mechanism of evolution that operates on some characters of individuals differently in relation to their sex. In a few cases, sexual selection is opposed to the processes of natural selection by the display of costly production structures (the handicap principle). I have researched different aspects of the honest display of behavioral traits in males and females of the black starling. My ultimate interest is to know the factors that affect the biological effectiveness and thus to be able to explain the evolution and stability of the sexual behaviors in these animals. The field work was carried out with the black starling on a plot of central Spain and with different species of the Sturnidae family in different habitats of Kenya.
Description of some biological processes using mathematical models.- Mathematical models allow the integrated formulation of a few biological processes. I am especially interested in those models that describe animal behavior and make predictions for future studies. In this sense I have investigated diverse aspects such as the shape of the circadian trajectories of weight, the optimal use of shelters against the predators, the survival of the expensive sex over other reproductive strategies and the adjustments of the investment of the reproduction parents in relation to the help of other individuals (cooperative breeding) or with the gender balance of the laying / litter.