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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2005.02.015 Byline: Joseph P. Poston, Dennis Hasselquist, Ian R.K. Stewart, David F. Westneat Abstract: Traits that influence social interactions (signals) are widely thought to be honest indicators of some underlying quality of their bearer. One hypothesis is that a signal and the bearer's immunocompetence are linked via a condition-dependent pathway. We tested this idea by measuring the effect of specific dietary components on the development of a melanin-based plumage signal and the production of antibodies in juvenile male house sparrows entering their first moult. We maintained sparrows on one of three artificial diets: high total protein, low total protein, or intermediate protein with the precursors of melanin, phenylalanine and tyrosine (PT), reduced by 50%. Diet did not affect survival or weight gain. Two aspects of male plumage differed between treatments; the white wing bar was significantly smaller in low-protein males, and the black bib feathers had significantly higher reflectance in PT-reduced males. PT reductions had no effect on bib size. PT-reduced birds also produced more antibodies to diphtheria and tetanus antigens than did other subjects. After repeating the experiment using a better control and a different diet formula to compensate for an energy imbalance resulting from reduced PT levels, PT reduction again produced lighter bib feathers, but the effect of diet on antibody production disappeared. We conclude that the amino acid precursors to melanin affect melanin synthesis if scarce in the diet, but in this case, do not affect size, the most conspicuously variable aspect of the signal. We found no evidence of a condition-dependent link between melanin synthesis and immunocompetence. Author Affiliation: (a) Department of Biology and Center for Ecology, Evolution, and Behavior, University of Kentucky, Lexington, KY, U.S.A. (a ) Department of Animal Ecology, Lund University, Lund, Sweden Article History: Received 11 August 2004; Revised 28 October 2004; Accepted 21 February 2005 Article Note: (miscellaneous) MS. number: A9969R

Behavioural studies show that mate choice and competition for mates are traits of natural selection, but the two mechanisms have not been studied interactively in a natural setting. A study of mate choice and competition for mates in the boat-tailed grackle is presented. Results show that indirect and direct mate choice can occur in the same species. It is shown that females choose mates which perform displays and which are more dominant. Details of the study are presented.

Species in which males directly defend groups of breeding females often have extreme skew in observed male mating success. In only a few species, however, has a corresponding skew in fertilization success been confirmed. Furthermore, the ecological and social factors contributing to variation in fertilization success need investigation. This study examined competition for mates and paternity in the boat-tailedgrackle (Quiscalus major). Observations at colonies of nesting females revealed that the topranking or alpha males performed more than 70% of the copulations. DNA fingerprinting indicated that alpha males sired less than 40% of nestlings. Nevertheless, analysis of band-sharing scores among nestlings from different nests suggested that alpha males sired more than three times as many offspring as any other individual male. Because few nestlings were sired by the nonalpha males that associated with colonies, females must have mated with other maleswhile on trips away from colonies. Analysis of paternity within broods revealed that at least half of all females had their brood fertilized by more than one male. Alpha males' success at fertilizing eggs did not vary with the number of simultaneously receptive females within a colony. Our results suggest that male and female behavior in female-defense polygyny results from complex coevolution of the sexes. [ABSTRACT FROM AUTHOR]

Climate change models often assume similar responses to temperatures across the range of a species, but local adaptation or phenotypic plasticity can lead plants and animals to respond differently to temperature in different parts of their range. To date, there have been few tests of this assumption at the scale of continents, so it is unclear if this is a large-scale problem. Here, we examined the assumption that insect taxa show similar responses to temperature at 96 sites in grassy habitats across North America. We sampled insects with Malaise traps during 2019-2021 (N = 1041 samples) and examined the biomass of insects in relation to temperature and time of season. Our samples mostly contained Diptera (33%), Lepidoptera (19%), Hymenoptera (18%), and Coleoptera (10%). We found strong regional differences in the phenology of insects and their response to temperature, even within the same taxonomic group, habitat type, and time of season. For example, the biomass of nematoceran flies increased across the season in the central part of the continent, but it only showed a small increase in the Northeast and a seasonal decline in the Southeast and West. At a smaller scale, insect biomass at different traps operating on the same days was correlated up to ~75 km apart. Large-scale geographic and phenological variation in insect biomass and abundance has not been studied well, and it is a major source of controversy in previous analyses of insect declines that have aggregated studies from different locations and time periods. Our study illustrates that large-scale predictions about changes in insect populations, and their causes, will need to incorporate regional and taxonomic differences in the response to temperature., (© 2023 The Authors. Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.)