Cooperative breeding systems are characterized by nonbreeding helpers that assist breeders in offspring care. However, the benefits to offspring of being fed by parents and helpers in cooperatively breeding birds can be difficult to detect. We offer experimental evidence that helper effects can be obscured by an undocumented maternal tactic. In superb fairy-wrens (Malurus cyaneus), mothers breeding in the presence of helpers lay smaller eggs of lower nutritional content that produce lighter chicks, as compared with those laying eggs in the absence of helpers. Helpers compensate fully for such reductions in investment and allow mothers to benefit through increased survival to the next breeding season. We suggest that failure to consider maternal egg-investment strategies can lead to underestimation of the force of selection acting on helping in avian cooperative breeders.

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Evolutionary theory suggests that alternative colour morphs (i.e. genetically controlled phenotypes) may derive similar fitness under frequency-dependent selection. Here we experimentally demonstrate opposing effects of frequency-dependent social environments on plasma hormone levels (testosterone and corticosterone) and immune function between red- and black-headed male morphs of the Gouldian finch (Erythrura gouldiae). Red-headed males are highly sensitive to changes in the social environment, especially towards the relative density of their own aggressive morph, exhibiting high stress responses and immunosuppression in socially competitive environments. In contrast, the non-aggressive black-headed males follow a more passive strategy that appears to buffer them against social stresses. The differential effect of hormones on aggressive behaviour and immune performance reinforces the contrasting behavioural strategies employed by these colour morphs, and highlights the importance of the social environment in determining the individual basis of behavioural and physiological responses.

Research over the past two decades has provided significant epidemiological and other evidence for the health benefits of the consumption of soy-based foods. A large number of dietary intervention studies have examined the effects of soy isoflavones on risk factors for cardiovascular disease and hormone-dependent cancers. However, these report large variability in outcome measures, very limited reproducibility between studies, and in some cases, controversy between the results of clinical trials using dietary soy or soy protein and isoflavone supplementation. This highlights a major gap in our understanding of soy isoflavone uptake, metabolism, distribution, and overall bioavailability. There are many potential factors that may influence bioavailability and a better knowledge is necessary to rationalize the inconsistencies in the intervention and clinical studies. This review focuses attention on our current state of knowledge in this area and highlights the importance of metabolism of the parent soy isoflavones and the critical role of gut microbiota on the bioavailability of these compounds and their metabolites.

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Male and female redpolls (Acanthis flammea) showed marked increases in circulating corticosterone up to 1 hour after exposure to a common stress-apture, handling and restraint-indicating that their hypothalamo-pituitary-adrenal axis responded to acute stress in a manner similar to that of other vertebrates. We used this protocol as a measure of responsiveness of the adrenocortical cells to acute stress in general and for comparison with gender and across seasons. In both sexes the adrenocortical response to stress was reduced in January (at Fairbanks, 64"N) and maximal when birds were breeding in June at Tbolik Lake (69"N). The elevation of circulating corticosterone following capture and handling in breeding males at Barrow (71'") was significantly less than in breeding males at Toolik Lake. There were also considerable variations among individuals in the intensity of the adrenocortical responses, particularly in the maximum levels of corticosterone attained. This individual variation correlated significantly with fat score andor body mass in both sexes only in breeding birds at Barrow. This difference may be explained by generally lower, and thus reduced variability in body fat and mass in birds sampled in the warmer climate of Toolik Lake. A similar trend was seen in non-breeding birds, but this was not significant. Additionally, in January, baseline cortisterone levels in males were correlated with body mass, although this relationship did not hold when both sexes were considered. Body mass and fat score in winter were similar to those of redpolls sampled at Barrow in June. These data suggest that redpolls may be able to adjust their responsiveness to acute stresses in relation t o fat stores. Those with greater fat depots had reduced responsiveness to stress.