Neonicotinoid pesticides exert metabolic effects on avian pollinators

Abstract

Neonicotinoids are neurotoxic systemic insecticides applied extensively worldwide. The impacts of common neonicotinoids like imidacloprid on non-target invertebrate pollinators have been widely studied, however effects on vertebrate pollinators have received little attention. Here, we describe the first study evaluating the effects of short-term (3 d) exposure to a range of environmentally relevant concentrations ($${0.2}\,\upmu \hbox {g g}^{-1}$$ 0.2 μ g g - 1 to $${2.5}\,\upmu \hbox {g g}^{-1}\cdot$$ 2.5 μ g g - 1 · Body Weight) of imidacloprid on wild-caught ruby-throated hummingbirds. Within 2 h of exposure, hummingbirds exhibited a significant depression in energy expenditure (up to $$25\% \pm 11\%$$ 25 % ± 11 % ). We did not observe significant effects on foraging behaviour measured in the subsequent 2 h to 4 h, although the effect size estimate was large (0.29). We also analyzed tissues collected 24 h after the final dose and did not observe significant effects on immune response or cholinesterase activity, although this may be related to our small sample size. We determined that hummingbirds excrete imidacloprid quickly (elimination half-life of $$2.1\hbox { h} \pm 0.1\hbox { h}$$ 2.1 h ± 0.1 h ) relative to other bird species. Hummingbirds have high energetic demands and store relatively little energy, especially during migration and breeding seasons. Therefore, changes in their metabolism following exposures to imidacloprid observed herein could bear important survivorship consequences for hummingbirds.

Current contrasting population trends among North American hummingbirds

“…High-density white-tailed deer populations in wooded habitats in North America significantly reduced species richness and abundance of intermediate canopy nesting songbirds 27 , where most hummingbirds build their nests. Additionally, chronic, widespread exposure to agrochemicals on breeding grounds may impact migratory hummingbirds [28][29][30] . Further study into the population-level effects of agrochemical exposure and invasive species in breeding grounds are warranted.…”

“…Forest fires pose a considerable threat to the productivity and species richness of tropical dry forests 37 , highlighting another risk to hummingbirds wintering in dry tropical forest regions. Additionally, reduced habitat quality on breeding grounds due to widespread agrochemical exposure may further impact the species [28][29][30] . Ruby-throated hummingbirds are arriving to breeding grounds up to 18 d earlier than they did historically in the northern parts of their range 38 .…”

Determination and dietary risk assessment of neonicotinoid and insect growth regulators in honey

“…Neonicotinoid insecticides are a class of pesticides that were introduced in the 1990s as replacement for organophosphate pesticides [1][2][3] . Due to their high efficacy for insect control and ease of application, neonicotinoids have quickly become the most widely used insecticides in agriculture, veterinary, and residential environments [4] .…”

Geographic and Temporal Variation in Annual Survival of a Declining Neotropical Migrant Hummingbird (Selasphorus rufus) Under Varying Fire, Snowpack, and Climatic Conditions

“…are more likely to migrate through lower-elevation landscapes, may make this class more vulnerable to anthropogenic stressors (Rousseau et al, 2020). The impact of exposure to pesticides with known avian reproductive, metabolic, and developmental effects within agricultural and forestry lands certainly warrants further study (Winnick and Dzialowski, 2013;Hoshi et al, 2014;Lopez-Antia et al, 2015;Bishop et al, 2018;English et al, 2021b) as does the possible loss of breeding habitat associated with herbicide use during forestry operations (Betts et al, 2013) and the impact of non-breeding habitat loss/degradation on juvenile survival (e.g., Wilson et al, 2018).…”