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

Abstract

SUMMARYCostly events in the life history cycle of organisms such as reproduction, migration and pelage/plumage replacement are typically separated in time to maximize their outcome. Such temporal separation is thought to be necessitated by energetical trade-offs, and mediated through physiological processes. However, certain species, such as tropical birds, are able to overlap two costly life history stages: reproduction and feather replacement. It has remained unclear how both events progress when they co-occur over extended periods of time. Here we determined the consequences and potential costs of such overlap by comparing molt and behavioral patterns in both sexes of captive zebra finches (Taeniopygia guttata castanotis) that were solely molting or were overlapping breeding and molt. Individuals overlapping the early stages of breeding with molt showed a roughly 40% decrease in the growth rate of individual feathers compared with birds that were molting but not breeding. Further, individuals that overlapped breeding and molt tended to molt fewer feathers simultaneously and exhibited longer intervals between shedding consecutive feathers on the tail or the same wing as well as delays in shedding corresponding flight feathers on opposite sides. Overlapping individuals also altered their time budgets: they devoted more than twice the time to feeding while halving the time spent for feather care in comparison to molt-only individuals. These data provide experimental support for the previously untested hypothesis that when molt and reproduction overlap in time, feather replacement will occur at a slower and less intense rate. There were no sex differences in any of the variables assessed, except for a tendency in females to decline body condition more strongly over time during the overlap than males. Our data indicate the existence of major consequences of overlapping breeding and molt, manifested in changes in both molt dynamics and time budgets of both sexes. It is likely that under harsher conditions in natural environments such consequences will be more severe and may result in fitness consequences.

Pre‐basic molt, feather quality, and modulation of the adrenocortical response to stress in two populations of rufous‐collared sparrows Zonotrichia capensis

“…Despite our observation of lower levels of corticosterone during molt, these levels were higher than those observed in temperate environments (Cornelius et al 2011). Although low levels of corticosterone suppression have been observed in several species of opportunistic breeders (Cornelius et al 2011, Echeverry-Galvis and Hau 2012, Buttemer et al 2015, these results could imply that these species tend to protect their feathers from detrimental effects of high corticosterone levels when molt occurs, although the mechanism by how this is achieved is unknown. One possibility is seasonal variations in corticosterone binding globulin (CBG) or glucocorticoid (GR) and mineralocorticoid receptors (MR), which act as a mediator for corticosterone to access tissues (Sapolsky et al 2000, Breuner and Orchinik 2001, Wingfield et al 2004.…”

A Trade-Off between Reproduction and Feather Growth in the Barn Swallow (Hirundo rustica)

“…Specifically, empirical evidence from field studies on the trade-off between reproduction and the ability to grow new feathers, which may select for maintenance of temporal disjunction between breeding and molt which is observed in so many species, is scant (e.g. [15], [17], [18], [34], [35], see also [36]). …”

Flight Performance and Feather Quality: Paying the Price of Overlapping Moult and Breeding in a Tropical Highland Bird

“…Also, tropical bird species with long wing moult durations are more likely to display the moult-breeding overlap [18]. Moreover, in captive Zebra finches ( Taeniopygia guttata ) overlapping individuals slow down feather growth rate and moult fewer feathers simultaneously compared to individuals just moulting [21], indicating that even under the benign conditions of captivity with ad libitum food availability individuals try to minimize trade-offs by reducing moult intensity. Conversely, temperate zone species that do not reduce moult intensity or speed when overlapping the final parts of their breeding cycle with moult experience trade-offs by facing lowered overwinter survival and reduced reproductive success in the next breeding season [11], [22].…”