Uropygial gland size: a marker of phenotypic quality that shows no senescence in a long-lived seabird
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Studies of senescence in the wild have traditionally focused on traits like survival or fecundity. Although efforts to measure other salient phenotypic traits and markers of relevant physiological processes are rapidly increasing, traits related to self-maintenance remain understudied in the context of aging. Uropygial or preen gland is a holocrine gland, exclusive to birds, directly linked to self-maintenance of the quality of plumage. We measured the size of uropygial glands of common gulls (Larus canus) in a cross sectional manner in order to test whether it shows the similar age-related decline as reproductive traits previously recorded in this species. Gulls with larger glands started breeding earlier in the season, indicating that gland size is a marker of individual phenotypic quality. We found a senescent decline in the onset of breeding and the size of white wing patches, a sexually dimorphic ornamental trait, while in contrast, preen gland increased with advancing age. This finding supports the view of life-history theory that in long-lived species whose lifetime reproductive success depends heavily on lifespan, self-maintenance is prioritized over reproduction. Altogether our results support the concept that senescence in the wild can be asynchronous for traits related to maintenance versus reproduction.
KeywordsAging Aging asynchrony Common gull Phenotypic quality Preen gland Senescence
Antonello Lorenzini provided constructive comments on the ms.
KR, TS and PH designed the study. JU, TS, RM and KR carried out the fieldwork. JU analyzed photos. PH, RM and JU carried out statistical analyses. TS, PH and JU drafted the manuscript. All authors gave final approval for publication.
This work was supported by the Estonian Ministry of Education (ETF7190) and Estonian Research Council (IUT21-1, IUT34-8).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All the data used for the study will be available through Dryad data repository after the manuscript’s acceptance.