Carlos de la Cruz

Testosterone and helping behavior in the azure-winged magpie (Cyanopica cyanus): natural covariation and an experimental test

In this study, we investigated patterns of natural covariation between testosterone and reproductive status in a cooperatively breeding bird species, the azure-winged magpie (Cyanopica cyanus). To assess the relationship between testosterone and breeding behavior, we also manipulated testosterone (T) levels early in the season (before breeding started) using testosterone-filled or empty implants. Our results do not support the hypothesis that circulating testosterone levels affect the occurrence of helping behavior in the azure-winged magpie. Helping males had similar T levels to breeding males. Furthermore, experimentally augmented plasma T did not affect the likelihood of becoming either a helper or a breeder. Overall, these results are consistent with previous findings in other bird species and only give some support to the behavioral suppression hypothesis, suggesting that helping in the azure-winged magpie is a flexible behavioral option moderated in the short-term by social and ecological factors. Experimentally elevated testosterone levels, however, reduced the reproductive success of male breeders because of markedly lower levels of paternal care, had similar effects on their mates, but had the contrary effect on helpers, which raised levels of parental effort. We suggest increases in the share of paternity and in social prestige as possible explanations for these results.

Positive correlation between helpers at nest and nestling immune response in a cooperative breeding bird

In cooperatively breeding species, helpers may contribute to the success of the brood by increasing the number of independent offspring, but also, they may affect offspring condition and, hence, their survival and recruitment into the breeding population. This second type of benefits is rarely included in theoretical models or assessed in field studies. Immune response is a good proxy of individual quality and fitness, and there is good evidence that the performance of the immune system of chicks during the nestling phase is related to their chances of survival and future reproduction. However, no study has so far explored whether helpers at the nest might contribute to enhance immune functioning of nestlings in species with a cooperative breeding system. Here we investigate this issue in the azure-winged magpie (Cyanopica cyanus) and found for the first time a positive correlation between the number of helpers at nest and the cell-mediated immune response of nestlings. This effect was not explained by a general improvement of body condition of chicks because it was independent of individual variation in body mass or tarsus length. Our results suggest that helping can have subtle effects on the quality of offspring that may influence their survival and future reproduction.

Life span and reproductive cost explain interspecific variation in the optimal onset of reproduction

Fitness can be profoundly influenced by the age at first reproduction (AFR), but to date the AFR–fitness relationship only has been investigated intraspecifically. Here, we investigated the relationship between AFR and average lifetime reproductive success (LRS) across 34 bird species. We assessed differences in the deviation of the Optimal AFR (i.e., the species‐specific AFR associated with the highest LRS) from the age at sexual maturity, considering potential effects of life history as well as social and ecological factors. Most individuals adopted the species‐specific Optimal AFR and both the mean and Optimal AFR of species correlated positively with life span. Interspecific deviations of the Optimal AFR were associated with indices reflecting a change in LRS or survival as a function of AFR: a delayed AFR was beneficial in species where early AFR was associated with a decrease in subsequent survival or reproductive output. Overall, our results suggest that a delayed onset of reproduction beyond maturity is an optimal strategy explained by a long life span and costs of early reproduction. By providing the first empirical confirmations of key predictions of life‐history theory across species, this study contributes to a better understanding of life‐history evolution.

Sex determination of Iberian Azure-winged Magpies Cyanopica cyanus cooki by discriminant analysis of external measurements

Like all corvids, the Azure‐winged Magpie Cyanopica cyanus is sexually monomorphic in plumage, making it difficult to distinguish between males and females in the field. We examined sexual size dimorphism in a population of Iberian Azure‐winged Magpies C.c. cooki and used a discriminant function analysis based on five morphological characters to determine the sex of first‐year and adult individuals. Females were significantly smaller than males for all tested variables within each age class except for keel length of first‐year individuals. In both sexes, wing length of adults was greater than that of yearlings, but only males showed significant differences in tail length between age classes (longer in first‐year birds). Stepwise discriminant analysis indicated that tail length and head plus bill length were the most accurate variables in a discriminant function model, predicting the sex of yearlings with about 90% accuracy. Adding wing length to the model yielded the same level of accuracy for adults. We propose a simple system to sex Iberian Azure‐winged Magpies, using only two or three variables easily measured in the field, which provides classification with a high level of accuracy.

Apparent absence of Cryptosporidium, Giardia and Toxoplasma gondii in three species of penguins along the Antarctic Peninsula

Abstract We carried out a study to investigate the presence of some protozoan parasites (Cryptosporidium sp., Giardia sp., Toxoplasma gondii) on three species of Antarctic penguins: Adélie (Pygoscelis adeliae), gentoo (Pygoscelis papua) and chinstrap (Pygoscelis antarctica) from different locations along the Antarctic Peninsula and the South Shetland Islands. Swabs and faeces samples were analysed by PCR assay for Cryptosporidium sp. and Giardia sp. while Toxoplasma was studied using serological methods from blood samples. We did not detect the presence of these organisms in the species studied. However, based on the upper values of the confidence intervals of the observed prevalence, their presence cannot be completely excluded.

No brood parasitism by the Great Spotted Cuckoo Clamator glandarius on the Azure-winged Magpie Cyanopica cyanus

Capsule No case of parasitic interaction was found after 12 years of intensive monitoring of a marked population in Spain where both species are sympatric. Aims To evaluate whether the Azure-winged Magpie is parasitized, and suggest possible causes that affect its relationship with the Great Spotted Cuckoo. Methods Data from a long-term field study of marked individuals in a population of Azure-winged Magpie in Spain, were collected from about 60 nests per year over 12 years. Results Although common in the area, no eggs or young of the Great Spotted Cuckoo were found in an Azure-winged Magpie nest. Conclusion The Great Spotted Cuckoo does not appear to parasitize the Azure-winged Magpie, and we suggest that elevated predation rates on nests may be an important, overlooked factor potentially affecting the choice of host species by this brood parasite.

MODE OF ATTACHMENT AND PATHOLOGY CAUSED BY PARORCHITES ZEDERI IN THREE SPECIES OF PENGUINS: PYGOSCELIS PAPUA, PYGOSCELIS ADELIAE, AND PYGOSCELIS ANTARCTICA IN ANTARCTICA

Abstract We identified and compared gross and microscopic lesions associated with the cestode, Parorchites zederi, in the digestive tracts of three species of penguins (Spheniscidae): the Chinstrap (Pygoscelis antarctica), Gentoo (Pygoscelis papua), and Adélie penguins (Pygoscelis adeliae). The gastrointestinal tracts of 79 recently dead individuals (71 chicks and eight adults) were collected in locations throughout the Antarctic Peninsula during summer field trips in 2006–09. Parorchites zederi was found in the small intestine of 37 animals (47%), and 23 (62%) of these had parasite-associated lesions. The cestodes were either free in the intestinal lumen, clustered within mucosal ulcers, or deeply embedded in the intestinal wall. Histopathologic changes were most severe in adult Gentoo Penguins and included transmural fibrogranulomatous enteritis, hemorrhage, and edema. This report of pathology associated with P. zederi in the digestive tracts of penguins can serve as reference to monitor health in Antarctic birds associated with environmental changes.

Exploratory behaviour modulates the relationship between colony familiarity and helping in a cooperative bird.

Individuals within animal groups may differ in personality and degree of familiarity raising the question of how this influences their social interactions. In Iberian magpies Cyanopica cooki, a portion of first-year males engage in cooperative behaviours and dispersal, allowing addressing this question. In this study, we first investigate the relationship between colony familiarity (native versus foreign) and reproductive status (breeding versus helping) of males during 21 years. Secondly, we measure the exploratory behaviour and monitor reproductive status of a sample of individuals with different colony familiarity during 2 years. Long-term monitoring revealed that foreign individuals were more likely breeders. The analysis on the subset of individuals in which exploratory behaviour was measured revealed a mediatory effect of exploratory behaviour in the association between colony familiarity and helping behaviour. Specifically, among foreign individuals, higher explorative males were more frequently involved in helping behaviour than lower explorative ones. Conversely, among native males, breeders were more explorative than helpers. Our results suggest that aspects of personality may mediate the value of familiarity in reproductive tasks in social species.