Current-use pesticides in tree swallow (Tachycineta bicolor) prey

Analysis of biological tissues or direct sources of food may better characterize exposure of non-target organisms to current-use pesticides. Food boluses were collected from tree swallow (Tachycineta bicolor) nestlings using a non-lethal, ligature method and were composited based on nest. The ligatures, which prevented the bolus from being swallowed, were placed on nestlings for 1 h until samples were collected. Samples in 2016 were collected from nestlings at 6 days and 12 days post-hatch whereas 2018 samples were collected from nestlings at 12 days post-hatch. Furthermore, in 2016 and 2018, insects commonly consumed by tree swallows were collected via sweep net and composited based on suborder (Brachycera, Nematocera, Zygoptera, or other) following identification via dichotomous keys. All samples were collected from an agricultural region of central Saskatchewan, Canada. Samples were freeze-dried and homogenized prior to extraction. A subsample was removed for analysis (the whole sample was used for those with a total mass less than 0.1 g). Following pressurized liquid extraction with 50/50 (v/v) acetone/dichloromethane, samples were cleaned-up via pass-through solid phase extraction using Oasis PRiME HLB cartridges (3 cc, 150 mg). All samples were analyzed for 170 current-use pesticides using gas chromatography and liquid chromatography tandem mass spectrometry (GC/MS/MS and LC/MS/MS). A total of 24 current-use pesticides and metabolites were detected in bolus samples (0.3-784.3 ng/g) and 19 current-use pesticides were detected in insects (0.2-1169.6 ng/g).