Interacting effects of cold snaps, rain, and agriculture on the fledging success of a declining aerial insectivore

Abstract

Climate change predicts the increased frequency, duration, and intensity of inclement weather periods such as unseasonably low temperatures (i.e., cold snaps) and prolonged precipitation. Many migratory species have advanced the phenology of important life history stages and, as a result, are likely to be exposed to these periods of inclement spring weather more often, therefore risking reduced fitness and population growth. For declining avian species, including aerial insectivores, anthropogenic landscape changes such as agricultural intensification are another driver of population declines. These landscape changes may affect the foraging ability of food provisioning parents and reduce the survival of nestlings exposed to inclement weather through, for example, pesticide exposure impairing thermoregulation and punctual anorexia. Breeding in agro-intensive landscapes may therefore exacerbate the negative effects of inclement weather under climate change. We observed that a significant reduction in the availability of insect prey occurred when daily maximum temperatures fell below 18.3 C, and thereby defined any day when the maximum temperature fell below this value as a day witnessing a cold snap. We then combined daily information on the occurrence of cold snaps and measures of precipitation to assess their impact on the fledging success of Tree Swallows (Tachycineta bicolor) occupying a nest box system placed across a gradient of agricultural intensification. Estimated fledging success of this declining aerial insectivore was 36.2% lower for broods experiencing 4 coldsnap days during the 12 days post-hatching period versus broods experiencing none, and this relationship was worsened when facing more precipitation. We further found that the overall negative effects of a brood experiencing periods of inclement weather was exacerbated in more agro-intensive landscapes. Our results indicate that two of the primary hypothesized drivers of many avian population declines may interact to further increase the rate of declines in certain landscape contexts.

Negative effects of agricultural intensification on the food provisioning rate of a declining aerial insectivore

“…It is thus imperative that future work focuses not only on how agricultural practices or global climate change independently impact declining avian species, but also on how these factors may interact with one another. This importance is due to the ability of growing broods or breeding parents to manage extreme weather is potentially lower within more agro-intensive landscapes (Eng et al, 2019;Evans et al, 2003;Garrett et al, 2022c;Grue et al, 1997;Tapper et al, 2020). Finally, our results provide evidence that aerial insectivore declines may be related to agricultural intensification through a trophic pathway.…”

The interacting effects of climate and land-use/land-cover changes on ecological communities

“…The one exception was the interaction between precipitation and cropland, where wetter conditions were associated with negative biodiversity outcomes and drier conditions were associated with positive biodiversity outcomes for both species richness and abundance regardless of changes in cropland. That neither species richness nor abundance responded to changes in cropland cover when there were simultaneous changes in precipitation is surprising since other research has shown that agriculture can exacerbate the negative effects of increased precipitation on fledging success (Garrett et al ., 2022) and impact differences in occupancy between wet and dry areas (Frishkoff et al ., 2016).…”

Cold stress initiates catecholaminergic and serotonergic responses in the chicken gut that are associated with functional shifts in the microbiome

“…Not surprisingly, cold stress has been widely demonstrated to increase avian mortality and susceptibility to enteric infection ( Mallmann, 1934 ; Thaxton et al, 1974 ; Soerjadi et al, 1979 ; Matsumoto and Huang, 2000 ; Borsoi et al, 2015 ). Indeed, the frequent and intense weather events ushered in by climate change, including rapid ambient temperature swings such as cold snaps, are of particular concern for avian species ( Garrett et al, 2022 ). Whether the stress-induced modulation of enteric neurochemical concentrations constitutes, in part, the mechanism driving avian susceptibility to infection following cold stress is unknown.…”