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Urbanization affects the ecology of wildlife diseases and although it has been suggested that there are lower risks of infection in urban areas, there have been no experiments to support this conclusion. We assessed haemosporidian prevalence and intensity in House Sparrows Passer domesticus using field and experimental data under contrasting conditions (i.e. urban vs. non‐urban). For experimental data, we kept 32 male House Sparrows in captivity as a proxy of stress, and for field data we sampled 49 House Sparrows (17 females). We made use of microscopy to determine the relative intensity and used the polymerase chain reaction to estimate infection prevalence. We obtained total leucocyte counts, leucocyte differentials, heterophil/lymphocyte ratio (H/L) as a measure of stress, and the Polychromatic Index as a measure of physiological condition (erythropoiesis). We identified a total of 10 haemosporidian lineages. For field samples (both males and females), we found a significantly higher prevalence of infection in non‐urban House Sparrows than in urban ones. Under experimental conditions, non‐urban House Sparrows showed a higher prevalence than urban ones both before and after captivity, with a significant increase in parasite intensity. The number of infected birds increased after captivity for both urban (~ 32%) and non‐urban House Sparrows (~ 19%), indicating either a recrudescence of chronic and relapses of latent infections or the appearance of infections that had been acquired earlier. The H/L ratio was significantly higher for non‐urban than for urban male House Sparrows before captivity. No difference in H/L was found for urban House Sparrows before and after captivity, indicating tolerance to city stressors. Our results showed a significant decrease in H/L for non‐urban birds after captivity, suggesting higher stress in the non‐urban agricultural environment. Haemosporidian infections were not associated with the H/L ratio. Our study provides evidence that highly urbanized areas within cities represent lower haemosporidian infection risks than do non‐urban areas for House Sparrows.

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Risk taking decisions related to the unpredictability of resource availability (risk‐sensitive foraging theory) have typically been explained by behavioral ecology and psychology approaches. However, little attention has been given to the physiological condition of animals as a factor that can influence the direction of foraging preferences. We evaluated the role of steroid hormones testosterone (T) and corticosterone (CORT) on the foraging preferences expressed by white‐eared hummingbirds Hylocharis leucotis in a risk‐sensitivity experiment. We recorded choices made by male individuals to floral arrays with constant and variable rewards (sugar concentration), and associated these with steroid hormone levels quantified at the start of the experiments. We found that males with higher T levels behave as risk‐prone foragers as they perform more visits to flower arrays with variable rewards. Interestingly, CORT levels were similar regardless whether individuals visited both types of array. According to our results, T seems to influence the foraging preferences of male hummingbirds. Individuals with higher levels of this hormone, made more rapid, frequent visits to flowers with variable rewards, and behave consistently as risk‐prone foragers, compared to males with low T levels. These are exciting avenues for future work, particularly considering recent evidence that individuals may exhibit behavioral differences, denoting an apparent personality, which may be associated with phisiological condition influencing how they respond behaviorally to environmental variation.

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although plumage coloration has been widely used as a model in studies of the evolution of signaling, the role of plumage in intrasexual communication has been less studied, especially in cases of the structural plumage color. The aim of our study was to use choice trials and plumage manipulation to test whether or not the structural blue color of the male Blue grosbeak (Passerina caerulea) works as a signal of social status. additionally, we tested whether or not females exploit signals used in aggression between males. if they do, it suggests that plumage coloration is also used in mate choice. in 2007, we captured males and females from two different populations. We performed two choice experiments by manipulating plumage color: (1) a status-signaling experiment, in which a male had to choose one of two other males, and (2) a mate-choice experiment, in which a female had to choose one of two males. Males clearly foraged near less blue birds during their first encounter and on the first day. However, this preference was not evident on subsequent days. females showed no preference for any color of male. Our data show that plumage color works as a "first impression" signal, which suggests that plumage coloration in the Blue grosbeak represents a signal of dominance status between unfamiliar individuals and thus supports the status-signaling hypothesis. Our results support previous evidence for a lack of selection of males by females, which for this species thus rebuts the armament-ornament model of sexual selection.La Coloración de Plumaje del Passerina caerulea no Tiene una función dual: un Test del Modelo armamentos-Ornamentos de la Selección SexualResumen. La coloración del plumaje ha sido ampliamente utilizada como modelo de estudio para comprender la evolución de la señalización. Sin embargo, pocos estudios han analizado el papel que tiene la coloración estructural del plumaje dentro de la comunicación intra-sexual. El objetivo de este estudio fue analizar si la coloración estructural del plumaje funciona como una señal de estatus social a través de experimentos de selección en los que se manipuló la coloración de plumaje de machos de Passerina caerulea. adicionalmente, se analizó si las hembras explotaban esta señal de agresión entre machos. Si esto último fuera así, sugeriría que la coloración del plumaje se utiliza también para escoger pareja. En 2007, se capturaron machos y hembras de dos poblaciones diferentes de P. caerulea. Se realizaron dos experimentos de selección mediante la manipulación del color del plumaje de los machos: (1) un experimento de señalización de estatus, el cual consistió en que un macho seleccionara a uno de otros dos machos para forrajear y (2) un experimento de selección de pareja, en el cual una hembra tuviera que elegir entre dos machos. Los resultados mostraron que los machos preferían forrajear con aquellos otros machos cuya coloración del plumaje era menos azul durante su primer encuentro y durante el primer día del experimento. Sin embargo, esta preferencia no fue evidente...

Behavior provides a useful framework for understanding specialization, with animal personality aiding our understanding of the invasiveness of birds. Invasions imply dispersion into unknown areas and could require changes in behavior or spatial clustering based on personality. Reduced neophobia and increased exploring behavior could allow individuals to colonize new areas as they test and use non–familiar resources. Here, we hypothesized that house sparrow (Passer domesticus) individuals from invasive populations would exhibit bolder behavior than in non–invasive populations. We assessed risk taking and neophobia in male house sparrows in Barcelona (where it is considered native) and in Mexico City (where it has become widely invasive), captured in two different habitats, urban and non–urban. We assessed latency to enter an experimental cage and to explore it, and latency to feed and feeding time in the presence of a novel object. We found that sparrows from Mexico City, both from urban and non–urban areas, were quicker to enter the experimental cage than the sparrows from Barcelona. The time it took the birds to start exploring the cage gave a similar result. We found no differences between cities or habitats in the latency to feed and feeding time while exposed to a novel object. Our results partially support the view that the invader populations from Mexico City are bolder than those from Barcelona. Behavior is an important component of plasticity and its variability may have an important effect on adaptation to local situations. Future studies should disentangle the underlying mechanisms that explain the different personalities found in populations of different regions, contrasting populations of different densities, and taking different food availability scenarios into account.

The role of badges as indicators of contest ability has been previously described. In hummingbirds, the exhibition of a badge is expected to save energy expenditure in agonistic interactions and to favor energy intake. Here, we investigate whether variable supercilium size in the white-eared hummingbird has a role in dominance status signaling. Firstly, 45 hummingbird males were captured and their superciliums were photographed to investigate variation in size and any possible allometric relationships. Secondly, 42 male birds were used to analyze whether the supercilium has a role in dominance status signaling in a dyadic contest. We found that supercilium size varied continuously but that despite variability between individuals, there was no relationship between supercilium size and body size. However, our dyad experiment indicated that birds with larger badges were able to make more visits to the feeders than individuals with smaller badges. We suggest a status signaling function of the supercilium.