Three strikingly different alternative male mating morphs (aggressive “Independents”, semi-cooperative “Satellites” and female mimic “Faeders”) coexist as a balanced polymorphism in the ruff, Philomachus pugnax, a lek-breeding wading bird1,2,3. Major differences in body size, ornamentation, and aggressive and mating behaviour are inherited as an autosomal polymorphism4,5. We show that development into Satellites and Faeders is determined by a supergene6,7,8 consisting of divergent alternative, dominant, non-recombining haplotypes of an inversion on chromosome 11, which contains 125 predicted genes. Independents are homozygous for the ancestral sequence. One breakpoint of the inversion disrupts the essential Centromere protein N (CENP-N) gene, and pedigree analysis confirms lethality of inversion homozygotes. We describe novel behavioural, testes size, and steroid metabolic differences among morphs, and identify polymorphic genes within the inversion that are likely to contribute to the differences among morphs in reproductive traits.

This paper provides an empirical examination of women's work histories following a first birth, their sex-role attitudes, and the relationship between attitudes and work history. In the light of these analyses, the aptness of Preference Theory as an explanation for the position of women in the British labour market is considered. Addressed in particular is Hakim's argument that the main determinant of women's heterogeneous employment patterns and work histories is heterogeneity in their preferences for differing combinations of family work and paid employment. Although support is found for Hakim's argument that employment careers are centrally important for only a minority of women, little evidence is adduced that it is preferences that distinguish the minority from the majority. The existence of a continuum of work-family preferences means that women with similar preferences (but differing capacities for overcoming constraints) will have very different labour market careers. Analysis of longitudinal data fails to support the central argument of Preference Theory that women in Britain and North America (countries where women live 'in the new scenario') have genuine, unconstrained choices about how they wish to live their lives. Instead, it is argued that a complete explanation of women's labour market choices after childbirth, and of the outcomes of those choices, depends as much on understanding the constraints that differentially affect women as it does on understanding their personal preferences.

This paper provides an empirical examination of women's work histories following a first birth, their sex-role attitudes, and the relationship between attitudes and work history. In the light of these analyses, the aptness of Preference Theory as an explanation for the position of women in the British labour market is considered. Addressed in particular is Hakim's argument that the main determinant of women's heterogeneous employment patterns and work histories is heterogeneity in their preferences for differing combinations of family work and paid employment. Although support is found for Hakim's argument that employment careers are centrally important for only a minority of women, little evidence is adduced that it is preferences that distinguish the minority from the majority. The existence of a continuum of work-family preferences means that women with similar preferences (but differing capacities for overcoming constraints) will have very different labour market careers. Analysis of longitudinal data fails to support the central argument of Preference Theory that women in Britain and North America (countries where women live 'in the new scenario') have genuine, unconstrained choices about how they wish to live their lives. Instead, it is argued that a complete explanation of women's labour market choices after childbirth, and of the outcomes of those choices, depends as much on understanding the constraints that differentially affect women as it does on understanding their personal preferences.

No abstract

We investigated whether nestling American robins (Turdus migratorius) were capable of influencing food distribution in their nests by perceiving that certain sectors of the nest received a relatively high proportion of feedings and positioning themselves accordingly.Feeding observations were obtained from videotape recordings taken at different stages of the nestling period. Parents generally arrived at a predictable location on the nest rim and allocated proportionally more food to nestlings in the central position. The degree of nestling movement was significantly positively correlated with variation in the predictability of parental arrival locations on the nest rim. Furthermore, nestlings moved more in broods suffering brood reduction. This suggests that when competition for food is intense and the location of parental arrival is predictable, nestlings respond by jockeying for access to the most favorable (i.e., central) position in the nest. We conclude that jockeying for position by nestlings can influence the pattern of food allocation by parents, and that hungry nestlings can improve their competitive standing against nestmates by moving to positions where parents are more likely to feed them.