Monitoring exposure of northern cardinals,Cardinalis cardinalis, to cholinesterase‐inhibiting pesticides: enzyme activity, reactivations, and indicators of environmental stress

Abstract

Northern cardinals (Cardinalis cardinalis) frequently use agricultural field edges in northeast Arkansas, USA, and may be at risk of exposure to cholinesterase (ChE)-inhibiting pesticides. We monitored northern cardinal exposure to ChE-inhibiting pesticides by comparing plasma total ChE (TChE) activity to reference-derived benchmarks and TChE reactivations. Total ChE and acetylcholinesterase (AChE) were measured for 128 plasma samples from 104 northern cardinals from nine study sites. Of birds sampled from sites treated with ChE-inhibiting pesticides, 4.3% of the samples had TChE activities below the diagnostic threshold (2 standard deviations [SD] below the reference mean) and 8.7% of the samples had TChE reactivations. No difference was found in TChE (p = 0.553) and AChE (p = 0.288) activity between treated and reference sites; however, activity varied among treated sites (p = 0.003). These data do not suggest uniform exposure to individuals, but rather exposure was variable and likely influenced by mitigating factors at individual and site scales. Furthermore, monitoring of TChE reactivation appeared to be a more sensitive indicator of exposure than the diagnostic threshold. Fluctuating asymmetry (FA) was greater at agricultural sites than reference sites (p = 0.016), supporting the hypothesis that FA may be useful for assessing a combination of habitat- and contaminant-related environmental stress.

Fluctuating asymmetry as a putative marker of human-induced stress in avian conservation

“…Roughly half of the studies measured more than one trait per individual, but only three studies combined information across traits, either by calculating a composite FA index (Maul and Farris 2005) or by treating multiple traits as repeated measurements at the level of the individual Van Dongen, 1999, Lens et al 2000). When organism-wide asymmetry (Individual Asymmetry Parameter, IAP; Clarke 1998) is expected, analyses that combine information across traits are believed to be more powerful in detecting relationships with stress and fitness than single-trait analyses (Leary and Allendorf 1989, Watson and Thornhill 1994, Leung et al 2000.…”

“…Only two studies Van Dongen 1999, Lens et al 2000) included secondary sexual traits (eye-rings, supercilia, length of tail streamers). While most studies met the basic statistical requirements of repeated measurements and correction for DA and AS, only three studies , Maul and Farris 2005 combined information across different traits. The majority of studies compared FA estimates at population level, while two studies (Anciães andMarini 2000, Cuervo andRestrepo 2007) additionally studied assemblage-level patterns.…”

Nutritional Stress Causes Heterogeneous Relationships with Multi-Trait FA in Lesser Black-Backed Gull Chicks: An Aviary Experiment

“…The tarsus is a relatively well-studied trait for fluctuating asymmetry in birds, and has been previously linked to a number of different stressors (see [38,39] for examples). The similar levels of tarsus FA between our stress treatments (Figure 2), and its mixed and mostly non-significant relationships with stress across the different hatching periods (Table 3) are therefore surprising and contrary to expectations.…”

Regional inhibition of cholinesterase in free‐ranging western pond turtles (Emys marmorata) occupying California mountain streams

“…One is to quantify the proportion of individuals in the contaminated sites that have ChE activity two standard deviations below the reference site mean ChE activity [35]. Another method is to identify the percentage of individuals that have ChE activities depressed by 20% of the reference mean [38]. Of the turtles sampled in the southern region of the present study, 6.3% of the turtles had ChE activity below the two standard deviation threshold and 75% of the turtles had ChE activity below the 20% diagnostic threshold.…”

“…At another agricultural site in the same study, 7% of the lizards were below the two standard deviation threshold. Maul and Ferris [38] found that at sites treated with ChE inhibitors, 3% of northern cardinals (Cardinalis cardinalis) were below the two standard deviation threshold and 34% were below the 20% diagnostic threshold.…”