Landscape context mediates the physiological stress response of birds to farmland diversification

Abstract

Farmland diversification practices are increasingly adopted to help reverse biodiversity declines in agroecosystems. However, evidence for the effectiveness of this approach often comes from documenting the species attracted to particular farming systems or landscapes, rather than their underlying physiological states that ultimately determine population growth or decline over the longer term. Across 38 organic, mixed‐produce farms spanning the US west coast, we quantified three physiological biomarkers that are widely used to capture variation in short‐ and long‐term stress responses for nine bird species with diverse life‐history traits. While controlling for other potentially confounding variables, we used multilevel models to examine the association between bird physiological conditions, landscape context and local farm management practices, including the integration of livestock, and cropland composition and configuration. Birds generally had lower stress responses on more‐locally diverse farms and in landscapes with higher amounts of semi‐natural cover. However, interactions between farm diversity and landscape context suggested birds were less stressed on more diverse farms in simpler landscapes, but more stressed and in poorer condition on more diverse farms embedded within complex landscapes. We found no differences in stress responses among birds in relation to their degree of human association (synanthropy), which suggests generality in our findings. Synthesis and applications. Birds were often less stressed on more diverse farms. However, these patterns were mediated by landscape context: birds were less stressed on more diverse farms in simplified landscapes, but more stressed on more diverse farms within complex landscapes. This means land managers might not see uniform effects of local diversification schemes across different landscape contexts. Our results underscore the need to consider responses related to physiological health status, in addition to species richness and abundance, to determine the effectiveness of farm management for biodiversity conservation.

Interactive effects of multiscale diversification practices on farmland bird stress

“…Latimer et al. (2020) also failed to find evidence that stress responses are mediated by species’ degrees of association with anthropogenic habitats (i.e., synanthropy). However, although we studied species that varied in their affiliation with agriculture, understanding stress responses of very rare species to farmland diversification practices was beyond the scope of our study (given the paucity of samples we collected for rare species).…”

“…A notable exception is Latimer et al. (2020), who found that avian stress tends to decline on diversified farms, especially in simplified landscapes with little surrounding noncrop vegetation.…”

“…However, while the integration of landscape ecology and conservation physiology has been proposed, studies that do so are rare (Ellis et al, 2012;Ziv & Davidowitz, 2019). A notable exception is Latimer et al (2020), who found that avian stress tends to decline on diversified farms, especially in simplified landscapes with little surrounding noncrop vegetation.…”

Agriculturally Intensified Landscapes Are Associated With Reduced Body Condition of Lady Beetles

“…the status of animal populations in disturbed landscapes before a numerical response is observed. For example, stress biomarkers in birds (Latimer et al 2020) and limb malformation in amphibians (Guerra and Aráoz 2016) respond to agricultural landscape composition and configuration. For arthropods, characteristics such as body size, mass, and lipid content are important indicators of body condition.…”

Leukocyte profile variation in Dupont’s Lark (Chersophilus duponti) in Spain and Morocco

“…Alternatively, the use of haematological parameters, such as the heterophil-to-lymphocyte ratio (hereafter H/L ratio) quantified in blood smears, is considered a reliable measure of long-term physiological stress on birds (Davis and Maney 2018;Gormally and Romero 2020), as they vary after some time (1-4 h depending on the species and the stressor's nature) since exposure to the stressor and they tend to endure longer than corticosterone levels in blood (Vleck et al 2000;Davis et al 2008;Müller et al 2011;Lebigre et al 2012;Goessling et al 2015;Davis and Maney. 2018;Skwarska 2018;Minias 2019;Latimer et al 2020).…”