Lack of seasonal and moult-related stress modulation in an opportunistically breeding bird: The white-plumed honeyeater (Lichenostomus penicillatus)

• Published in: Hormones and behavior Vol. 76; pp. 34 - 40
• Main Authors: Buttemer, William A., Addison, BriAnne A., Astheimer, Lee B.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2015; Elsevier BV
• Subjects: Animals; Australia; Aves; Birds; Corticosterone; Corticosterone - metabolism; Corticosterone suppression; Female; Male; Molting - physiology; Moult; Moult/breeding overlap; Opportunistic breeding; Passeriformes - metabolism; Passeriformes - physiology; Reproduction - physiology; Seasons; Sexual Behavior, Animal - physiology; Stress; Stress modulation; Vertebrates; White-plumed honeyeater; Australia; Opportunistic breeding; Stress modulation; Corticosterone; Moult/breeding overlap; White-plumed honeyeater; Moult; Corticosterone suppression
• ISSN: 0018-506X; 1095-6867
• DOI: 10.1016/j.yhbeh.2015.02.002

This article is part of a Special Issue “SBN 2014”. In most vertebrate species, glucocorticoid levels and stress sensitivity vary in relation to season and life-history stage. In birds, baseline corticosterone (CORT) and stress sensitivity are typically highest while breeding and decrease substantially during moult. Because elevated CORT adversely affects protein synthesis, moult-related CORT suppression is thought to be necessary for forming high-quality feathers. Surprisingly, some passerine species lack moult-related CORT suppression, but these are distinguished by having slow rates of moult and being opportunistic breeders. We examined baseline and stress-induced CORT levels in an opportunistically breeding Australian passerine, the white-plumed honeyeater (Lichenostomus penicillatus). Although this species has a slower moult rate than high-latitude breeders, it differs little from north-temperate passerines. Neither baseline nor stress-induced CORT levels varied with season (winter, spring or summer), sex or moult status in adult birds. While breeding tended to be highest in early spring through late summer, laparotomies revealed only limited reduction in testicular size in males the year round. In all but one sampling period, at least some females displayed follicular hierarchy. Breeding usually coincides with outbreaks of phytophagous insects, which can happen at any time of the year. This results in moult/breeding overlap when infestations occur in late spring or summer. The ability of this species to moult and breed at the same time while having breeding-levels of CORT demonstrates that CORT suppression is not a prerequisite for synthesis of high-quality feathers. An experimental design incorporating moulting and non-moulting phenotypes is suggested to test the functional significance of CORT suppression in other species. •Corticosterone (CORT) did not vary seasonally in adult white-plumed honeyeaters.•CORT levels were not affected by moult status in these birds.•The lack of CORT modulation is consistent with their year-round breeding readiness.•A protocol to test the significance of moult-related CORT suppression is described.