Differential selection according to the degree of cheating in a status signal

The maintenance of honesty in a badge-of-status system is not fully understood, despite numerous empirical and theoretical studies. Our experiment examined the relationship between a status signal and winter survival, and the long-term costs of cheating, by manipulating badge size in male house sparrows, Passer domesticus . The effect of badge-size manipulation on survival was complex owing to the significant interactions between the treatments and original (natural) badge size, and between the treatments and age classes (yearlings and older birds). Nevertheless, in the experimental (badge-enlargement) group, males with originally large badges had increased winter survival, while males with originally small badges had decreased survival. This indicates that differential selection can act on a trait according to the degree of cheating.

Division of Labor: Incubation and Biparental Care in House Sparrows (Passer Domesticus)

In the great majority of animal taxa, males do not participate in parental care, but substantial paternal care is common across avian species. We examined male and female incubation contributions in House Sparrows (Passer domesticus), quantifying the incubation behavior of free-living, individually color-banded parents during 47 nesting cycles. We also measured the relative warmth of male and female incubation surfaces. Females spent more time incubating than their male partners, and female time incubating served as the best single predictor for hatching success. Considered alone, male time incubating correlated negatively with hatching success, but that effect was nullified when female incubation was taken into account. Females had warmer abdomens than males, a difference that may reflect greater development of brood patch and effectiveness of incubation in that sex. Here, male badge size was not demonstrably associated with either male or female incubation patterns or hatching success.División de Labores: Incubación y Cuidado por Ambos Progenitores en Passer domesticus