Male ornaments function as honest cues of male quality in many species and are
subject to intra- and intersexual selection. These ornaments are generally studied during
peak expression, however their size outside the breeding season may determine
ultimate ornament size and costliness, and as such reproductive success. We investigated
whether male black grouse Lyrurus tetrix eye comb size was related to age,
condition and measures of male dominance before and during the breeding season.
Total combined eye comb size began to increase ~70 d before the start of the breeding
season. Adult males (aged ≥ 2 yr old) had consistently larger eye combs than younger
males (1 yr old) both before and during the breeding season. Heavier and more dominant
adult males (attending the lek more frequently and successfully reproducing) had
larger eye combs. For younger males, those that were heavier had larger eye combs.
Additionally, males that spent more time on the lek showed increased eye comb size
as the breeding season approached. Overall we find that ornament size is positively
related to dominance and condition before and during the breeding season. Since
dominance is accrued through year-round interactions in many species, the ability to
maintain larger signals over prolonged periods, including outside of the breeding season,
is likely to be beneficial for adults. For younger males, it is likely that they cannot
sustain or are constrained from producing larger eye combs over long periods of time.
They therefore prioritise growth of their ornaments later, and according to the amount
of time they spend on the lek