Relationships among timing of moult, moult duration and feather mass in long‐distance migratory passerines

Abstract

Moult is a costly but necessary process in avian life, which displays two main temporal patterns within the annual cycle of birds (summer and winter moult). Timing of moult can affect its duration and consequently the amount of material invested in feathers, which could have a considerable influence on feather structure and functionality. In this study, we used two complementary approaches to test whether moult duration and feather mass vary in relation to the timing of moult. Firstly, we conducted a comparative study between a sample of long‐distance migratory passerine species which differ in moult pattern. Secondly, we took advantage of the willow warbler's Phylloscopus trochilus biannual moult, for which it is well‐known that winter moult takes longer than summer moult, to assess between‐moult variation in feather mass. Our comparative analysis showed that summer moulting species performed significantly shorter moults than winter moulters. We also detected that feathers produced in winter were comparatively heavier than those produced in summer, both in between‐species comparison and between moults of the willow warbler. These results suggest the existence of a trade‐off between moult speed and feather mass mediated by timing of moult, which could contribute to explain the diversity of moult patterns in passerines.

Molt–breeding overlap alters molt dynamics and behavior in zebra finches,Taeniopygia guttata castanotis

“…The tendency of the overlappers to lose more body condition over time suggests that the costs of the overlap were not fully compensated, even under the benign conditions of captivity. It is possible, however, that aspects of feather quality could have been compromised in overlappers, such as feather mass or structure (Dawson et al, 2000;DesRochers et al, 2009;De la Hera et al, 2010;Strochlic and Romero, 2008;Maenniste and Horak, 2011). Further characterizations of feather structural properties in relation to molt/breeding overlap are needed to resolve this question.…”

“…Reproduction is estimated to increase daily basal metabolic rate by approximately 25-50% [egg production (King, 1973;Ricklefs, 1974;Monaghan and Nager, 1997); incubation (De Heij et al, 2008)] and molt byquality whereas for molt it would maximize feather quality and minimize deficits in flight performance (Jenni and Winkler, 1994;De la Hera et al, 2010). Indeed, in species where molt co-occurs with the end of the reproductive period, feather structure is compromised (Hemborg, 1999;Dawson et al, 2000), adult movements are restricted and survival decreases (Stearns, 1992;Hemborg and Lundberg, 1998).…”

Feather growth rate and mass in Nearctic passerines with variable migratory behavior and molt pattern

“…obs.). Recent research also shows that ptilochronology-based measurements of growth rate on tail feathers produced during a complete molt process are able to predict the production of feathers of higher quality than shorter molts (Dawson et al 2000, Serra 2001, Griggio et al 2009, de la Hera et al 2010b, Serra et al 2010, so selection will tend to maximize the investment of time and energy in feather production. However, the amount of time that can be allocated to molt is expected to be constrained by the temporal requirements of other important activities of the annual cycle with which molt normally does not overlap, such as breeding and migration (de la Hera et al 2009a, Rohwer et al 2011.…”

“…Interestingly, some intraspecific studies have shown that a shortening of summer molt duration might be associated with a reduction in the mass and quality of feathers (Dawson et al 2000, de la Hera et al 2009b). Although there is no empirical evidence to support the extrapolation of previous patterns to the interspecific level, it has been suggested that the tradeoff between molt speed and feather mass might explain why some long-distance migratory species, which are extremely time-constrained after breeding but can occupy areas with suitable environmental conditions for molting during periods other than summer (Moreau 1972, Barta et al 2008, have adopted drastic changes in the timing of their annual complete molt (Svensson and Hedenström 1999, Hall and Tullberg 2004, de la Hera et al 2010b.…”

“…Interestingly, some intraspecific studies have shown that a shortening of summer molt duration might be associated with a reduction in the mass and quality of feathers (Dawson et al 2000, de la Hera et al 2009b). Although there is no empirical evidence to support the extrapolation of previous patterns to the interspecific level, it has been suggested that the tradeoff between molt speed and feather mass might explain why some long-distance migratory species, which are extremely time-constrained after breeding but can occupy areas with suitable environmental conditions for molting during periods other than summer (Moreau 1972, Barta et al 2008, have adopted drastic changes in the timing of their annual complete molt (Svensson and Hedenström 1999, Hall and Tullberg 2004, de la Hera et al 2010b.A large part of our knowledge of the relationship between migration and molt in passerines comes from the study of Western Palearctic species, for which we have information on molt duration for many species, obtained using a comparable methodology (see Ginn and Melville 1983). However, few data regarding molt duration are available in other biogeographic contexts (Ryder and Wolfe 2009, Bridge 2011), where the ecological pressures acting on birds could be dramatically different, thereby promoting the appearance of molting strategies rarely present in Palearctic species.…”