Expression of annual cycles in preen wax composition in red knots: constraints on the changing phenotype

Abstract

Birds living in seasonal environments change physiology and behavior in correspondence to temporally changing environmental supplies, demands and opportunities. We recently reported that the chemical composition of uropygial gland secretions of sandpipers (Scolopacidae, order Charadriformes) changes during the breeding season from mixtures of monoesters to diesters, which fulfill specific functions related to incubation. A proper temporal match between the expression of diester preen waxes and incubation requires a flexible organization of the trait. Here we analyze the possible degrees of flexibility with reference to the functionality of better-understood molt and body mass cycles of free-living and captive red knots (Calidris canutus). The relative flexibility of seasonal cycles in preen wax composition was examined by two experimental perturbations: (1) giving birds restricted access to food and (2) monitoring them long-term under a constant photoperiodic regime. We found that wax type cannot change instantaneously, but that changing the type of wax is under similar organizational time constraints as the replacement of feathers. Just as molt and mass cycles, the seasonal rhythm of diester secretion appeared to be under endogenous control: most birds placed in a constant photoperiod still maintained seasonally changing preen waxes. Diester preen wax secretion was synchronized with the peak in body mass in spring, but became less well expressed under constant photoperiodic conditions and when food availability was limited.

Limited Access to Food and Physiological Trade‐Offs in a Long‐Distance Migrant Shorebird. II. Constitutive Immune Function and the Acute‐Phase Response

“…These birds were left in their cages to keep group sizes consistent; however, their immune measurements were not included in the data set (leaving , 9 females, 10 males). n p 19 We manipulated access to food following Reneerkens et al (2007) using a predictable feeding regime (i.e., food was available at the same times every day). Birds had access to food (Trouvit trout food pellets, Vervins, France) either 6 h a day (0900-1100 hours and 1300-1700 hours) or 22 h a day (22 h vs. 24 h of food a day did not result in significant changes in body mass [Vézina et al 2009] or constitutive immunity [D. M. Buehler, unpublished data]).…”

Flyway evolution is too fast to be explained by the modern synthesis: proposals for an ‘extended’ evolutionary research agenda

“…Interestingly, and arguing for a hard-wired programming of annual cycles, the seasonal phenotypic changes shown outdoors are maintained by Red Knots and Great Knots Calidris tenuirostris kept in photoperiodic-and temperature-constant indoor environments (Piersma 2002;Reneerkens et al 2007;Piersma et al 2008). When adult birds of the contrasting subspecies islandica and rufa are brought into similar conditions in captivity, they show very distinct annual cycles (Fig.…”

“…3). Birds of the islandica subspecies typically show a single mass peak in spring and carry their alternate plumage relatively briefly (see also Piersma 2002;Reneerkens et al 2007), whereas rufa Knots in captivity show two mass peaks and carry the alternate plumage much longer. If the divergence of the flyways of rufa and islandica Knots really represent historic rather than prehistoric phenomena, this raises the compelling question as to how shorebirds could adjust migration-related traits so quickly.…”

Fat quill secretion in pigeons: could it function as a cosmetic?

“…Preen gland secretions have been hypothesized to function in olfactory communication (Balthazart and Schoff eniels, 1979 ) or crypsis (Reneerkens et al, 2002 ;Reneerkens et al, 2005 ;Reneerkens, 2007 ). Such olfactory crypsis could also be important for both sexes in pigeons, which equally share incubation.…”