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

Abstract

A temporal separation of energetically costly life history events like reproduction and maintenance of the integumentary system is thought to be promoted by selection to avoid trade-offs and maximize fitness. It has therefore remained somewhat of a paradox that certain vertebrate species can undergo both events simultaneously. Identifying potential costs of overlapping two demanding life history stages will further our understanding of the selection pressures that shape the temporal regulation of life history events in vertebrates. We studied free-living tropical Slaty brush-finches (Atlapetes schistaceus), in which individuals spontaneously overlap reproduction and moult or undergo both events in separation. To assess possible costs of such an overlap we quantified feather quality and flight performance of individuals in different states. We determined individual’s life history state by measuring gonad size and scoring moult stage, and collected a newly grown 7th primary wing feather for later analysis of feather quality. Finally, we quantified flight performance for each individual in the wild. Overlapping individuals produced lighter and shorter wing feathers than individuals just moulting, with females decreasing feather quality more strongly during the overlap than males. Moreover, overlapping individuals had a reduced flight speed during escape flights, while their foraging flight speed was unaffected. Despite overlappers being larger and having a smaller wing area, their lower body mass resulted in a similar wing load as in breeders or moulters. Individuals measured repeatedly in different states also showed significant decreases in feather quality and escape flight speed during the overlap. Reduced escape flight speed may represent a major consequence of the overlap by increasing predation risk. Our data document costs to undergoing two life history stages simultaneously, which likely arise from energetic trade-offs. Impairments in individual quality and performance may represent important factors that select for temporal separation of life history stages in other species.

Habitat selection in transformed landscapes and the role of forest remnants and shade coffee in the conservation of resident birds

“…Birds undergoing primary feather moults typically associated with annual complete moults have high energy demands and are compromised in their ability to fly; consequently, this activity is usually undertaken when and where resources are high (Echeverry‐Galvis & Córdoba‐Córdoba, ; Echeverry‐Galvis & Hau, ). We interpret higher probabilities of capturing individuals undergoing active primary moults as an indication of better performance in a habitat.…”

“…Since breeding‐related activities such as incubation and food provisioning are energy demanding, their timing and location are typically constrained by resource availability (Echeverry‐Galvis & Córdoba‐Córdoba, ; Echeverry‐Galvis & Hau, ). We interpret a higher probability of capturing individuals with evidence of active breeding as an indication of better performance in a habitat.…”

Dietary flavonoids advance timing of moult but do not affect redox status of juvenile blackbirds (Turdus merula)

“…This is highlighted by several studies where feather moult has been shown to be traded against competing energydemanding processes, such as reproduction, migration and pre-migratory fuel accumulation (e.g. Rubolini et al, 2002;Echeverry-Galvis and Hau, 2013;Saino et al, 2014). Energy is required for feather keratin and pigment synthesis, for buffering the temporary loss of insulation during body feather replacement, and (in the case of flight feather moult) to compensate for the reduced foraging efficiency due to impaired mobility (Murphy, 1996).…”

Moult in the Loggerhead Shrike Lanius ludovicianus is influenced by sex, latitude and migration

“…The time required to produce quality replacement plumage, without significantly increasing daily costs (Hoye & Buttemer ), ultimately determines moult scheduling (Cornelius et al . , Echeverry‐Gavlia & Hau , Saino et al . , Kiat & Izhaki ).…”