Does anthropization affect physiology, behaviour and life‐history traits of Montagu's harrier chicks?

Abstract

The last century has seen a steep decline in biodiversity, and anthropization is considered one of the major drivers of this decline. Anthropogenic disturbances, due to human presence and/or activities, may be perceived as chronic stressors by wildlife and potentially lead to deleterious effects on traits related to fitness. The main objective of the present study was to highlight the effects of these anthropogenic elements on wild birds on sparsely urbanized farmland, far less studied than in urbanized areas. We investigated during four successive breeding seasons whether the anthropization level, assessed by infrastructure density around nests, and the harvesting conditions around nests may impact physiological, behavioural and life‐history traits of Montagu's harrier Circus pygargus chicks. Higher anthropization levels were associated with higher basal corticosterone levels in nestlings during only one breeding season and a lower body condition at fledging for females, probably because they suffered from higher starvation than males. Nestlings reared in more anthropized areas or in harvested crops before their fledging harboured more fault bars on rectrices than those reared in less anthropized areas or in unharvested crops regardless of year and sex, which is suggestive of higher stress during development. Nestling behaviours were also impacted by anthropization level and harvesting conditions: chicks in harvested crops were more aggressive and in areas with higher anthropization levels more prone to escape than others. Because Montagu's harrier is a protected species, the impacts highlighted in the present study are a matter of concern, especially regarding farmland landscape modifications, and we advise limiting perturbations in areas where Montagu's harriers usually nest.

Meta-analysis reveals between-population differences affect the link between glucocorticoids and population health

“…For example, a decade ago, hair cortisol concentration was identified as a highly useful metric for polar bear ( Ursus maritimus ) population health ( Vongraven et al, 2012 ), and since then, glucocorticoids have been linked to health effects precipitated by sea ice change ( Boonstra et al, 2020 ) and associated nutritional stress ( Mislan et al, 2016 ). In other species of conservation concern, including wood frogs ( Lithobates sylvatica, Tennessen et al, 2018 ) and Montagu's harrier ( Circus pygarus, Rabdeau et al, 2022 ), similar associations have been made between glucocorticoids and environmental and suspected threats to population health. Given their link to fitness, glucocorticoids have become a staple indicator for populations and species most vulnerable to environmental change.…”