Cholinesterase inhibition in tree swallows (Tachycineta bicolor) and eastern bluebirds (Sialia sialis) exposed to organophosphorus insecticides in apple orchards in Ontario, Canada

Abstract

Apple orchards occupy approximately 12,565 ha of land in Ontario, Canada, and are treated with the greatest number and applications of pesticides among all agricultural crops within the province. The potential for exposure to wildlife from frequent organophosphorus (OP) spray applications is therefore considerable. This study investigated the impact of agricultural spray applications of azinphos‐methyl, diazinon, phosalone, and phosmet in apple orchards on the cholinesterase (ChE) activity of wild birds nesting in orchards. These four OP pesticides ranked among the most widely used insecticides used on all fruit crops in Ontario in 1988. Tree swallows (Tachycineta bicolor) and eastern bluebirds (Sialia sialis) were chosen as monitor species because they commonly breed and forage within apple orchards, utilize different feeding strategies, and are readily attracted to nest boxes. Brain and plasma ChE activities were determined for nestling bluebirds and swallows, and plasma ChE was measured in adult swallows for comparison with nestling data. In adult tree swallows, mean plasma ChE levels were significantly inhibited 41% compared to controls 12 h after a second application of azinphos‐methyl. Mean plasma ChE activity in another group of adult tree swallows dropped by 21 and 19% following a multiple phosmet application. In nestlings, brain ChE activities obtained postspray often fell below predicted activities calculated from control siblings. This trend was especially apparent in the younger nestlings, less than 6 d old. However, for bluebirds the rates of increase of brain ChE with age in nestlings from treated sites was significantly lower than in nestlings from control sites. Brain ChE activity of two nestlings found dead following a phosalone application gave no indication that insecticide exposure was responsible. No other dead or moribund birds were discovered during the course of the study. Sequential plasma sampling of siblings, before and after OP application, was beneficial in reducing the required number of nests sampled by one half, but plasma ChE was less reliable overall than brain ChE in indicating exposure. Results of depressed ChE levels in tree swallows and eastern bluebirds inhabiting apple orchards are consistent with avian species in other orchard monitoring studies. No indication was found that OP exposure due to agricultural spraying in apple orchards adversely affected the survival of the birds we monitored.

Effects of pesticide spraying on chick growth, behavior, and parental care in tree swallows (Tachycineta bicolor) nesting in an apple orchard in Ontario, Canada

“…However, a significant decrease occurred in feeding trips in the orchard after the second OP insecticide application. The decline in feeding trips after the second spray is consistent with the pattern of inhibited ChE activities found in adult tree swallows in 1989 in the orchard studied here and several nearby orchards [14]. In 1989, tree swallows did not exhibit significant plasma ChE depression after a single OP insecticide exposure but did experience significant ChE inhibition after the next OP insecticide spray event.…”

Multiple Lines of Evidence Risk Assessment of Terrestrial Passerines Exposed to PCDFs and PCDDs in the Tittabawassee River Floodplain, Midland, Michigan, USA

“…Site-specific assessments of exposures and related effects for a variety of terrestrial passerine species have been conducted (Ankley et al 1993; Bishop et al 1995; Custer et al 2001; Henning et al 2003; Arenal et al 2004; van den Steen et al 2006, 2007), but more commonly, tree swallows have been selected as target species in assessments of risk in aquatic-based studies (Shaw 1983; DeWeese et al 1985; Beaver 1992; Ankley et al 1993; Bishop et al 1995; Froese et al 1998; Custer et al 1998; Secord et al 1999; Custer et al 2000; Harris and Elliott 2000; Custer et al 2002, 2003; Echols et al 2004; Custer et al 2005; Smits et al 2005; Neigh et al 2006b; Spears et al 2008). However, house wrens and eastern bluebirds have been effectively used as receptors at terrestrially contaminated study sites (Thiel et al 1988; Burgess et al 1999; Custer et al 2001; Mayne et al 2004; Neigh et al 2006a). …”

Passerine Exposure to Primarily PCDFs and PCDDs in the River Floodplains Near Midland, Michigan, USA

“…Eastern bluebirds prefer open grassland habitats and feed by dropping on prey from an elevated perch, whereas house wrens primarily glean insects off foliage in brushy/forested habitats. Several studies of contaminants have used eastern bluebirds and house wrens (Burgess et al 1999; Custer et al 2001; Henny et al 1977; Mayne et al 2004; Neigh et al 2006a, 2007). …”