Use of feathers to assess polychlorinated biphenyl and organochlorine pesticide exposure in top predatory bird species of Pakistan

Little is known about the levels of organochlorines (OCs) in predatory bird species from Asia or the factors governing their concentrations. This study is the first report on concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in predatory birds of Pakistan. The concentrations of PCBs and OCPs were investigated using tail feathers of ten different species of predatory birds. In addition, concentration differences among body, tail, primary and secondary feathers were investigated for six individuals of black kite (Milvus migrans). Ranges of concentrations were highest for dichlorodiphenyldichloroethylene (p,p′-DDE: 0.11–2163 ng g^{− 1} dry wt.) followed by dichlorodiphenyltrichloroethane (p,p′-DDT: 0.36–345 ng g^{− 1} dry wt.), hexachlorobenzene (HCB: 0.02–34 ng g^{− 1} dry wt.), ∑ PCBs (0.03–16 ng g^{− 1} dry wt.) and trans-nonachlor (TN; 0.01–0.13 ng g^{− 1} dry wt.). CB 118, 153, 138, and 180 along with p,p′-DDE were found as the most prevalent compounds. ∑ PCBs and ∑ DDTs were significantly different among species (both p < 0.01) and omnivorous, scavengers, carnivorous and piscivorous trophic guilds (all p < 0.03). Only ∑ PCBs were significantly differentamong different families of birds (p < 0.01). Values of stable isotopes (δ¹³C and δ¹⁵N) differed significantly (all p < 0.01) among species, families, trophic guilds as well as terrestrial and aquatic habitat but not between nocturnal and diurnal predators (p = 0.22 for δ¹³C; p = 0.50 for δ¹⁵N). Concentrations of ∑ PCBs, ∑ DDTs and trans-nonachlor, but not HCB (p = 0.86), were significantly different among different feather types (all p < 0.01). Trophic and taxonomic affiliation as well as dietary carbon sources (δ¹³C) for species were identified as the variables best explaining the observed variation in exposure to the studied compounds. The significance of contributing factors responsible for OC contamination differences in predatory birds should be further elucidated in future studies. - Highlights: • First assessment of PCBs and OCPs using feathers of predatory birds from Pakistan • Combined influence of various factors explain PCBs and OCPs concentrations • Intra- and interspecific differences were observed for OCs concentrations. • Bioaccumulation of PCBs and OCPs varied significantly among feather types • Trophic, taxonomic affiliation and dietary proxies best explain PCBs and OCPs level.