title: Plumage quality mediates a life-history trade-off in a migratory bird.
abstract: BACKGROUND
  Moult is one of the most costly activities in the annual cycle of birds and most avian species separate moult from other energy-demanding activities, such as migration. To this end, young birds tend to undergo the first post-juvenile moult before the onset of migration, but in some species the time window for the pre-migratory feather replacement is too narrow. We hypothesized that in such species an increased investment in the structural quality of juvenile feathers may allow to retain juvenile plumage throughout the entire migratory period and delay moult until arriving at wintering grounds, thus avoiding a moult-migration overlap.
  
  
  METHODS
  The effect of juvenile plumage quality on the occurrence of moult-migration overlap was studied in a migratory shorebird, the common snipeGallinago gallinago. Ca. 400 of first-year common snipe were captured during their final stage of autumn migration through Central Europe. The quality of juvenile feathers was assessed as the mass-length residuals of retained juvenile rectrices. Condition of migrating birds was assessed with the mass of accumulated fat reserves and whole-blood hemoglobin concentration. Path analysis was used to disentangle complex interrelationships between plumage quality, moult and body condition.
  
  
  RESULTS
  Snipe which grew higher-quality feathers in the pre-fledging period were less likely to initiate moult during migration. Individuals moulting during migration had lower fat loads and hemoglobin concentrations compared to non-moulting birds, suggesting a trade-off in resource allocation, where energetic costs of moult reduced both energy reserves available for migration and resources available for maintenance of high oxygen capacity of blood.
  
  
  CONCLUSIONS
  The results of this study indicate that a major life-history trade-off in a migratory bird may be mediated by the quality of juvenile plumage. This is consistent with a silver spoon effect, where early-life investment in feather quality affects future performance of birds during migration period. Our results strongly suggest that the juvenile plumage, although retained for a relatively short period of time, may have profound consequences for individuals' fitness.
authors.affiliation: Department of Biodiversity Studies and Bioeducation, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland.
authors.forename: Patrycja
authors.initials: P
authors.lastname: Podlaszczuk
authors.affiliation: Department of Ecology and Vertebrate Zoology, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Kamiński
authors.affiliation: Department of Biodiversity Studies and Bioeducation, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland.
authors.forename: Radosław
authors.initials: R
authors.lastname: Włodarczyk
authors.affiliation: Medical University of Łódź, Sterlinga 1/3, 91-425 Łódź, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Kaczmarek
authors.affiliation: Department of Biodiversity Studies and Bioeducation, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Janiszewski
authors.affiliation: Department of Biodiversity Studies and Bioeducation, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Minias
keywords: Common snipe; Feather quality; Gallinago gallinago; Haemoglobin concentration; Life-history; Moult-migration overlap