The maintenance of genetic variation is a long-standing issue because the adaptive value of life-history strategies associated with each genetic variant is usually unknown. However, evidence for the coexistence of alternative evolutionary fixed strategies at the population level remains scarce. Because in the tawny owl (Strix aluco) heritable melanin-based coloration shows different physiological and behavioral norms of reaction, we investigated whether coloration is associated with investment in maintenance and reproduction. Light melanic owls had lower adult survival compared to dark melanic conspecifics, and color variation was related to the trade-off between offspring number and quality. When we experimentally enlarged brood size, light melanic males produced more fledglings but in poorer condition, and they were less often recruited in the local breeding population than those of darker melanic conspecifics. Our results also suggest that dark melanic males allocate a constant effort to raise their brood independently of environmental conditions, whereas lighter melanic males finely adjust reproductive effort in relation to changes in environmental conditions. Color traits can therefore be associated with life-history strategies, and stochastic environmental perturbation can temporarily favor one phenotype over others. The existence of fixed strategies implies that some phenotypes can sometimes display a “maladapted” strategy. Long-term population monitoring is therefore vital for a full understanding of how different genotypes deal with trade-offs.
Recruitment in relation to paternal coloration
Father ID: identity of the father; Mother ID: identity of the mother; Year when experiment carried out; Treatment = brood size treatment; Father and mother color: from 5 (light melanic) to 1 (dark melanic); Mass Fledgling: mean body mass of fledglings; Nb recruits: number of fledglings that were recruited in the local breeding population
Tawny owl color - Recruitment.xls
Analysis of dispersal distance in relation to coloration
Recruit ring= Identity of the individual that dispersed; dispersal distance: distance (m) between the nest where the recruit was reared and the nest where it bred for the first time; Year = year when born; Brood ID: identity of the nest where the recruit was raised; Sex=Sex of the recruit; Treatment: brood size manipulation; Father and mother color: 1 for dark melanin to 5 for light melanic
Tawny owl Dispersal distance recruits.xlsx
Tawny owl color-specific reproductive success Year1
Male ring: identity of the breeding male; Year: year when experiment carried out; Nb Fledglings: number of fledglings; Father and mother color: from 1 (dark melanic) to 5 (light melanic); Hatch date: hatching date in number of days to 1st January; BroodSizebefore: number of nestlings before treatment was applied; Treatment: brood size manipulation experiment
Tawny owl color-specific survival
Ring: identity of the breeding individual; Year: year when captured; Brood ID: identity of the nest where the individual bred; Treatment: Enlarged is for when we added nestlings to the brood, Reduced when we removed nestlings, N when no treatment was applied and absence of code is for non-breeding individuals; Coloration: between 1 (dark melanic) to 5 (light melanic); sex: sex of the individual
Reproductive success after having applied brood size manipulation experiment in two successive years
Male Ring: Identity of the breeding male; Year X2: second year of brood size manipulation experiment; N_Fledglings X2: number of fledglings in the second year; Hatch date X2: hatching date in the second year (number of days after 1st January); Treatment X1: brood size manipulation in the first year; Treatment X2: brood size manipulation in the second year; Class Treatment: 1 (reduced-reduced), 2 (enlarged-reduced), 3 (reduced-enlarge), 4 (enlarged-enlarged); Father color: color of the father (1 for dark melanic to 5 for light melanic)
Tawny owl color-specific reproductive success 2successiveYear.xlsx
Tawny owl Color-specific offspring body mass
Fledging Body Mass: mass at fledging (g); Year: Year when the experiment was performed; BroodID: identity of the nest where fledglings were raised; Hour: time of the day when weighed; Wing: wing length (mm); Sex: sex of the fledgling; Cross fostered: No is for when fledglings were raised by their biological parents and Yes is for when fledglings were raised by foster parents; Father and mother color: 1 for dark melanic to 5 for light melanic; Treatment: brood size manipulation experiment