Spatial, temporal, and dietary determinants of organic contaminants in nestling tree swallows in Point Pelee National Park, Ontario, Canada

Abstract

Point Pelee National Park of Canada in southwestern Ontario, an important migratory route and vital breeding area for many birds, has localized areas of organochlorine (OC) pesticide contamination from agricultural production during the 1950s and 1960s. During 2001 and 2002, we investigated movement of persistent contaminants through the food web with the insectivorous tree swallow (Tachycineta bicolor) as a sentinel. The a priori site classifications, contaminated or reference, were based on soil residues of dichlorodiphenyltrichloroethane (DDT) and its breakdown products (sigmaDDT), dieldrin, and other OC pesticides. In 2001, all nestling tissue samples were pooled by site, and residue levels did not reflect the soil contaminant status. To improve sampling accuracy in 2002, tissue residues were determined from birds in individual nests. This showed OC pesticides to be higher in samples from contaminated sites compared with reference sites (p = 0.031). Polychlorinated biphenyls (PCBs), which were not detected in soil samples, were present in the nestlings and were not related to site of origin (p = 0.422). In 2002, dietary samples were collected from nestlings and identified to taxon, and representative insects collected from nesting sites were analyzed for PCBs and other OCs. Consumption of terrestrial prey was positively correlated with tissue residues of sigmaDDT (p = 0.006), whereas PCBs came from aquatic prey, Hexagenia mayflies (p = 0.003). Dietary details proved valuable in this study of contaminant transfer in insectivorous vertebrates.

Dietary exposure of three passerine species to PCDD/DFs from the Chippewa, Tittabawassee, and Saginaw River floodplains, Midland, Michigan, USA

“…When feasible, it is important to quantify site-specific dietary composition since variations in prey selection can influence dietary exposure estimates (Neigh et al 2006a;Papp et al 2007;Smits et al 2005). Literature-based estimates of tree swallow ingestion of Dipterans were 15-20% (ww; Johnson and Lombardo 2000;McCarty and Winkler 1999;Neigh et al 2006a) compared to 52% in the current study.…”

“…Profiles of the relative concentrations of individual PCDD/DF congeners in samples of invertebrates and bolus at SAs on the Tittabawassee River downstream of the source of contamination were dominated by 1,2,3,4,6,7,8,9Introduction Site-specific dietary exposure to polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) was determined for three cavity-nesting, insectivorous passerine species downstream of Midland, Michigan (USA). Tree swallows (Tachycineta bicolor), which eat primarily emergent aquatic invertebrates (McCarty 1997;McCarty and Winkler 1999;Mengelkoch et al 2004), have been shown to have exposure links to contaminated sediments (Custer et al 1998;Echols et al 2004;Maul et al 2006;Neigh et al 2006c;Papp et al 2007;Smits et al 2005). House wrens (Troglodytes aedon) and eastern bluebirds (Sialia sialis) have been used to assess the contaminant exposure of terrestrial insectivores at locations with contaminated soils (Neigh et al 2006a).…”

“…The mixture of chlorinated hydrocarbons in the SA is dominated by a few PCDF congeners, which makes it distinctive compared to other locations contaminated with PCB mixtures or PCDDs (Custer et al 2002(Custer et al , 2005Froese et al 1998;Harris and Elliott 2000;Neigh et al 2006b, c;Secord et al 1999;Shaw 1983;Smits et al 2005;Spears et al 2008). Furthermore, based on chemical characteristics and best estimates of historical production data, it is likely that this unique mixture has been in place for almost a century, with most of the materials being released prior to the 1950s (ATS 2007(ATS , 2009.…”

“…PCDFs and related chlorinated hydrocarbons are persistent and lipophilic (Mandal 2005) and have a great potential to accumulate through the food web Custer et al 1998;Kay et al 2005;Maul et al 2006;Russell et al 1999;Smits et al 2005;Wan et al 2005). Because of the elevated soil and sediment concentrations in the SA (Hilscherova et al 2003) and low avian dietary exposure thresholds (Custer et al 2005;Eisler 2000;Nosek et al 1992), the authors investigated the potential for the accumulation of PCDFs and PCDDs from invertebrates to resident insectivorous birds.…”

“…In particular, concentrations of chlorinated hydrocarbons and the congener profiles of the relative concentrations of congeners have been shown to be site-specific (Custer and Read 2006;Maul et al 2006;Papp et al 2007). Site-specific dietary composition is related to the prevailing invertebrate abundance (Custer et al 2005;Echols et al 2004;Neigh et al 2006a;Nichols et al 1995;Quinney and Ankney 1985;Smits et al 2005;Wayland et al 1998) and the timing of nest initiation (Custer et al 1998;Maul et al 2006;Papp et al 2007), especially for tree swallows that prey primarily on emergent aquatic invertebrates to feed nestlings (Blancher and McNicol 1991;Johnson and Lombardo 2000;McCarty and Winkler 1999). Site-specific residue concentrations in egg and nestling tissues have been studied for a variety of chlorinated hydrocarbons and species (Ankley et al 1993;Bishop et al 1995;Custer et al 1998Custer et al , 2003Custer et al , 2005Froese et al 1998;Henning et al 2003;Neigh et al 2006a, b, c;Spears et al 2008).…”