DOI: 10.5061/dryad.dc37q
title: Data from: Biomarker of burden: feather corticosterone reflects energetic expenditure and allostatic overload in captive waterfowl

description: 1.Allostatic load describes the interplay between energetic demand and
 availability and is highly context dependent, varying between seasons and
 life history stages. When energy demands exceed physiological set points
 modulated by glucocorticoid hormones, individuals may experience
 allostatic overload and transition between stages in sub-optimal
 physiological states. 2.Corticosterone, the major glucocorticoid hormone
 regulating energy expenditure in birds, is incorporated into growing
 feathers (CORTf), and it has been suggested that CORTf reflects long-term
 records of allostatic load during feather growth. However, relationships
 between allostatic load and CORTf have not been adequately evaluated. If
 such relationships exist, the use of CORTf to investigate cross-seasonal
 effects could provide novel insights into impacts of past allostatic load
 and/or overload events. 3.We tested whether experimental increases in
 daily workload during two adjacent life history stages would be reflected
 in CORTf levels, and examined if CORTf levels reflected either current
 energetic demand or allostatic load prior to feather growth. 4.Daily
 workloads in female mallard (Anas platyrhynchos) ducklings were increased
 over a 6-week period using physical obstacles and/or carrying back-mounted
 weights. We measured daily energy expenditure, growth, body mass, and
 CORTf in growing ducklings. Then, we induced feather moult and reapplied
 combinations of workload treatments for an additional 6 weeks to
 investigate whether effects of past energetic demands would be detected in
 future CORTf levels. 5.Ducklings confronted with higher workloads during
 development had reduced body mass, growth rates, and consequently higher
 daily energy expenditure and CORTf values compared to controls. When
 ducklings were fully developed, CORTf patterns in birds re-exposed to
 workload treatments reflected only current, rather than past, energetic
 demands. However, under allostatic overload conditions, past levels of
 CORTf were associated with CORTf in the subsequent moult. 6.Our study
 confirms the previously untested assumption that CORTf reflects energetic
 demand during the period of feather growth in a precocial bird. We show
 that allostatic overload conditions early in life, which temporarily
 supress growth, can be detected using CORTf; an event potentially missed
 in studies which rely solely on measures of body condition alone. 7.We
 suggest that CORTf can provide a valuable biomarker of allostatic load and
 overload conditions during the period of feather growth, but highlight how
 context should be considered for studies using CORTf to investigate
 influences of carry-over effects. Our study contributes to building a
 physiological foundation to inform interpretations of ecological patterns
 using CORTf.
description: Measurements of body
 mass, energy expenditure and feather corticosterone in captive Mallard
 ducklingsThis data set contains
 morphometric (body mass, feather size) and physiologic (daily energy
 expenditure, feather corticosterone) measurements obtained from female
 mallard ducklings, collected in a captive experimental setting. Four
 spreadsheets are contained within the .xlsx file, including: Legend -
 describes each of the variables; Treatments - body mass, duckling age and
 experimental treatment over all phases of the experiment; DEE - daily
 energy expenditure obtained from doubly labeled water; and Feathers -
 measures of feather corticosterone and feather size for both phase one and
 phase twoBiomarker_of_burden_Johns_et_al_2017_data.xlsx