Data from: Size, ornamentation, and flight feather morphology promote within-pair paternity in a sexually dimorphic passerine

Morphology in sexually dimorphic species is related to increased
opportunity for sexual selection when traits reflect individual quality.
In socially monogamous species, it may function to increase variance in
reproductive success if exaggerated traits are related to the opportunity
to engage in extra-pair paternity (EPP). Nonetheless, it is poorly
understood if ornamental versus functional traits are differentially
related to the distribution of paternity across individuals. We examined
EPP in the Scissor-tailed Flycatcher (Tyrannus forficatus), a sexually
dimorphic suboscine passerine, to determine how flight feather morphology
(both ornamental and related to flight performance), ornamental
coloration, and flight performance were related to paternity for males and
females. We assessed paternity at 140 nests across 7 years and found that
73% of nests contained extra-pair young with 59% of nestlings resulted
from extra-pair fertilizations. Males that secured paternity with their
social mate had larger size (wing chord and tail length), better body
condition, and more exaggerated ornamental traits (color, primary notch,
and streamer length) than cuckolded males. When compared directly to the
social males they cuckolded, however, cuckolders had shorter primary
notches and had duller coloration. Elongated flight feather features were
associated with greater maneuverability during flight, and longer primary
notches and tail streamers were associated with maintenance of within-pair
paternity, possibly via flight displays. Females that cuckolded their
mates had less exaggerated flank coloration but better body condition than
those that did not. We posit that in this system there is a lack of strong
selection on extra-pair mate morphology; rather, high quality males
maintained WPP while females in good condition were more likely to cuckold
social males of poorer quality, signaling a role of reciprocal selection
in extra-pair mate choice.