Glucocorticoids link forest type to local abundance in tropical birds

Abstract

Selective logging is a major driver of environmental changes in the tropics. Recently, there has been increasing interest in understanding which traits make bird species resilient or vulnerable to such changes. Physiological stress mediated by the steroid hormone corticosterone (CORT) might underlie changes in local abundance of species because it regulates a range of body functions and behaviours to maintain homeostasis in changing environments. We conducted a 3‐year study to assess (a) the variation in CORT levels in feathers (where CORT is deposited during the moult) of 10 understorey bird species across both unlogged old‐growth forest and selectively logged forest in Borneo, (b) how this variation is associated with within‐year variation in population abundance between forest types and (c) whether the difference in feather CORT (fCORT) between co‐specific populations living in unlogged and logged forests in 1 year is related with their difference in population abundance the following year. We used effect size estimates to measure standardized magnitude and direction of fCORT changes between unlogged and selectively logged forest. We found small to large effect sizes, indicating large among‐species variation in physiological acclimatization to changes in forest conditions. In 2016 and 2018, species with relatively higher fCORT in unlogged forest were relatively more abundant in logged forest in the same year; in 2017, species with relatively higher fCORT in logged forest were relatively more abundant in logged forest. Importantly, we found that for a given species, the difference in fCORT at year (x) between unlogged and logged forests was negatively related with a difference in its local abundance between the two forest types in the following year (x + 1). Our results point to glucocorticoid hormones as potential mediators of carry‐over effects on population abundance due to direct and indirect effects of silvicultural practices in tropical forests of Borneo, suggesting fCORT as a potential marker of population changes. A free Plain Language Summary can be found within the Supporting Information of this article.

Impacts of selective logging on the oxidative status of tropical understorey birds

“…The inclusion of phylogeny in the LMs (see Supporting Information) did not change significantly the outcomes, thus we report only results of non‐phylogenetic models. To estimate the RPA index of each species, we used captures data of birds for each type of forest relative to our study period, as follows: ([captures in logged forest – captures in unlogged forest]/[captures in logged forest + captures in unlogged forest]; inverse of logging sensitivity index; Hamer et al., 2015; Messina, Edwards, Marasco, et al, 2020). Positive values of the RPA index indicate higher abundance of the species in selectively logged forest compared to unlogged forest.…”

Abiotic niche predictors of long-term trends in body mass and survival of Eastern Himalayan birds

“…A meta-analysis of avian response to logging revealed that species also have lowered immunity in logged forests in comparison with old-growth forests (Messina et al 2018), and were likely to carry higher disease loads. Furthermore, glucocorticoid levels have been shown to have carry-over effects on population dynamics in many bird species (Harms et al 2015; Hansen et al 2016; Messina et al 2020).…”

Validation of an enzyme immunoassay for the detection of corticosterone metabolites from northern bobwhite (Colinus virginianus) feces

“…Research into ruffed grouse ( Bonasa umbellus ) found that fecal cort metabolite (FCM) levels differed based on an individual’s roosting location and that FCM concentrations decreased as snow depth increased ( Shipley et al, 2019 ; Shipley et al, 2021 ). Messina et al (2020) found that feather cort level predicted relative abundance of several tropical bird species for the year following sampling, and the trend was stronger in logged forests compared to undisturbed forest areas. Research on black grouse ( Tetrao tetrix ) using FCM concentrations showed that disturbance by recreational winter activities could increase daily energy expenditure by as much as 10% ( Arlettaz et al, 2015 ).…”