Song recognition and heterospecific associations between 2 fairy-wren species (Maluridae)

Although heterospecific associations beneficial to one or both species involved (e.g. commensalisms or mutualisms) are common, it is generally assumed that interactions between species are transient and not particular to individuals. However, long-term interactions between individuals of different species do occur. In such heterospecific social groups, discrimination between heterospecific individuals may be beneficial, allowing individuals to direct beneficial or aggressive behaviors towards appropriate targets. Here, we describe heterospecific groups composed of splendid and variegated fairy-wrens (Malurus splendens and M. lamberti) and provide the first experimental evidence that recognition of heterospecific group members occurs across species. In these species, family groups live on overlapping territories and co-defend shared territories against both heterospecific and conspecific intruders. Individuals on shared territories were frequently observed traveling and foraging together. Socially dominant males of both species responded more aggressively to songs of neighboring and foreign heterospecific fairy-wrens than they did to those of their co-resident heterospecifics. Although splendid fairy-wrens did not change their behavior when associating with heterospecifics, variegated fairy-wrens spent more time foraging, were less vigilant, had greater first-nest fledging success, and fewer extra-group young. These findings suggest heterospecific associations between these 2 species benefit the variegated fairy-wren. Our findings are novel and show that recognition and discrimination among individuals, often considered a prerequisite for conspecific cooperation, can occur across species. Includes supplementary materials

I like who you like, but only if I like you: Female character affects mate-choice copying.

Mate-choice copying is shown when women imitate the mate-choice preferences of other women. We propose that the preferences of women with a pleasant character should be more influential than those of women with an unpleasant character and further suggest that this should apply only when the female demonstrates active interest in the male, rather than disinterest. Here, we presented women as having either a pleasant or unpleasant character and found that observing pleasant women looking at men increased women’s preferences for those men, while observing unpleasant women looking at men had no effect on women’s preferences. Furthermore, the effect of being looked at by a pleasant woman was heightened when she was smiling. This suggests that judgements of facial attractiveness can be socially influenced and that character affects the degree of influence

High refractive index of melanin in shiny occipital feathers of a bird of paradise

Male Lawes's Parotia, a bird of paradise, use the highly directional reflection of the structurally colored, brilliant-silvery occipital feathers in their courtship display. As in other birds, the structural coloration is produced by ordered melanin pigmentation. The barbules of the Parotia's occipital feathers, with thickness ~3 µm, contain 6–7 layers of densely packed melanin rodlets (diameter ~0.25 µm, length ~2 µm). The effectively ~0.2 µm thick melanin layers separated by ~0.2 µm thick keratin layers create a multilayer interference reflector. Reflectance measurements yielded peak wavelengths in the near-infrared at ~1.3 µm, i.e., far outside the visible wavelength range. With the Jamin-Lebedeff interference microscopy method recently developed for pigmented media, we here determined the refractive index of the intact barbules. We thus derived the wavelength dependence of the refractive index of the barbules' melanin to be 1.7–1.8 in the visible wavelength range. Implementing the anatomical and refractive index data in an optical multilayer model, we calculated the barbules' reflectance, transmittance and absorptance spectra, thereby confirming measured spectra