Fledging mass is color morph specific and affects local recruitment in a wild bird

TY - JOUR

T1 - Fledging mass is color morph specific and affects local recruitment in a wild bird

AU - Morosinotto, Chiara

AU - Brommer, Jon E.

AU - Lindqvist, Atte

AU - Ahola, Kari

AU - Aaltonen, Esa

AU - Karstinen, Teuvo

AU - Karell, Patrik

PY - 2020

Y1 - 2020

N2 - Early-life conditions may have long-lasting effects on life history. In color polymorphic species, morph-specific sensitivity to environmental conditions may lead to differential fitness. In tawny owls (Strix aluco), pheomelanin-based color polymorphism is expected to be maintained because the brown morph has higher adult fitness in warmer environments, while selection favors the gray morph under colder conditions. Here we investigate body mass at fledging and its consequences until adulthood in a population at the species’ cold range margin. Using 40 years of data (1979–2017), we show that brown pairs, which mainly produce brown offspring consistent with a one-locus-two-alleles inheritance model, consistently raised heavier offspring than mixed (gray-brown) pairs and gray pairs. Offspring mass declined seasonally, except among offspring raised by brown pairs. Brown offspring could be heavier because of morph-specific parental care and/or offspring growth. Furthermore, mass at fledging is associated with fitness: the probability of local recruitment into the breeding population increased with higher mass at fledging, especially in mild winters and with favorable food conditions, although recruitment is not morph specific. Fledgling mass thus provides a fitness benefit in terms of recruitment probability that is modulated by environmental factors, which appear to level off any direct morph-specific recruitment benefits.

AB - Early-life conditions may have long-lasting effects on life history. In color polymorphic species, morph-specific sensitivity to environmental conditions may lead to differential fitness. In tawny owls (Strix aluco), pheomelanin-based color polymorphism is expected to be maintained because the brown morph has higher adult fitness in warmer environments, while selection favors the gray morph under colder conditions. Here we investigate body mass at fledging and its consequences until adulthood in a population at the species’ cold range margin. Using 40 years of data (1979–2017), we show that brown pairs, which mainly produce brown offspring consistent with a one-locus-two-alleles inheritance model, consistently raised heavier offspring than mixed (gray-brown) pairs and gray pairs. Offspring mass declined seasonally, except among offspring raised by brown pairs. Brown offspring could be heavier because of morph-specific parental care and/or offspring growth. Furthermore, mass at fledging is associated with fitness: the probability of local recruitment into the breeding population increased with higher mass at fledging, especially in mild winters and with favorable food conditions, although recruitment is not morph specific. Fledgling mass thus provides a fitness benefit in terms of recruitment probability that is modulated by environmental factors, which appear to level off any direct morph-specific recruitment benefits.

KW - Body mass

KW - Early-life condition

KW - Life-history strategy

KW - Parent-offspring morph

KW - Plumage coloration

KW - Winter temperature

U2 - 10.1086/710708

DO - 10.1086/710708

M3 - Article

C2 - 33064585

AN - SCOPUS:85092261601

VL - 196

JO - American Naturalist

JF - American Naturalist

SN - 0003-0147

IS - 5

ER -