Reproductive success and biochemical effects in tree swallows (Tachycinetabicolor) exposed to chlorinated hydrocarbon contaminants in wetlands of the Great Lakes and St. Lawrence River basin, USA and Canada

Reproduction and biochemical indicators (vitamin A, ethoxyresorufin-O-deeth ylase [EROD], highly carboxylated porphyrins) of contaminant effects, and c oncentrations of organochlorine residues were measured in tree swallows fro m wetlands within the watersheds of the Great Lakes and the St. Lawrence Ri ver, USA and Canada. To assess the vitamin A sources in the tree swallow di ets, insects were collected, by ligature, from nestlings at four of these s ites. Diet samples were analyzed for retinol and alpha- and beta-carotene. Marked differences were found in chlorinated hydrocarbon residues in eggs a nd nestlings among sites; however, we did not find any significant differen ces in hatching or hedging success. The maximum polychlorinated biphenyl (P CB) concentration found was 11.1 mu g/g in eggs from Akwesasne Reserve, New York, USA, on the St. Lawrence River, whereas the highest p,p'-DDE concent ration of 2.57 mu g/g was found in eggs from Mud Creek, Ontario, Canada, in the Lake Erie watershed. Concentrations of other organochlorine pesticides and chlorobenzenes were low and not variable among sites. Significant diff erences in hepatic EROD activity, retinol and retinyl palmitate, and uropor phyrin in nestling birds existed among sites. Ethoxyresorufin O-deethylase activity was highest and retinol and retinyl palmitate were lowest at Cornw all Island, Ontario, Canada, in the St. Lawrence River, whereas porphyrins were highest at Toronto and Hamilton harbors, Ontario, Canada, in Lake Onta rio. Ethoxyresorufin O-deethylase induction was significantly and negativel y correlated with nestling hepatic retinol concentrations, whereas uroporph yrin concentrations were positively correlated with PCB congener 118 in nes tlings. In contrast, few differences occurred in vitamin A concentrations i n diet samples among sites. Together, these findings suggest that depressed hepatic vitamin A and elevated highly carboxylated porphyrin concentration s are strongly associated with sites with the highest organochlorine exposu re in tree swallows.