Productivity of Tree Swallows (Tachycineta bicolor) Exposed to PCBs at the Kalamazoo River Superfund Site

Abstract

A 123-km stretch of the Kalamazoo River in Michigan, was designated a Superfund site in 1990 due to historical releases of effluent containing polychlorinated biphenyl (PCB)-contaminated paper waste. Risk to bird species in the river ecosystem was evaluated using the tree swallow (Tachycineta bicolor) as a monitor for possible effects due to PCB exposure at two nesting locations, one in the Superfund site and one in an upstream reference location that is less contaminated with PCBs. In 2 of the 3 years of the study, clutch size at the contaminated location was 3.7 ± 1.4 and 4.8 ± 0.73 eggs per nest (mean ± SD), which was significantly less than the clutch size at the reference location (5.0 ± 1.1 and 5.3 ± 1.1 eggs per nest). However, there were no statistically significant differences in fledging success, predicted brood size, predicted number of fledglings, or growth of nestlings between the Kalamazoo River Superfund site and an upstream reference location with lesser concentrations of PCBs in the sediments and riparian soils. Productivity and hatching success comparisons between these same sites were also not significantly different; however, the power of these conclusions was less (p < .10). The reduction in clutch size at the co-contaminated location could not be attributed to PCBs due to a number of confounding factors, including Co-cocontaminants, habitat structure, and food availability. Other reproductive parameters were not significantly impaired, and the size of the newly established colony at the Kalamazoo River Superfund site continued to grow over the period of the study. These site-specific observations, combined with multiple lines of evidence approach that considered results reported for the effects of both total PCBs and 2,3,7,8 tetrachlorodibenzo-p-dioxin equivalents (TEQ) on tree swallows at other locations, suggest that there were no significant population-level effects of PCBs on tree swallows at the Kalamazoo River Superfund site.

Notes

^a Percentage of eggs hatched in each nest.

^b Percentage fledged per nestling hatched.

^c Percentage fledged per egg laid.

^d Significantly different from the FC reference population (Mann–Whitney U, p < 0.05).

^e Significantly different from the FC reference population (Mann–Whitney U, p < 0.05).

^f Significantly different from the FC reference population (Mann–Whitney U, p < 0.05).

^a Nests in which at least one nestling fledged.

^b Nests containing eggs and/or nestlings but without an adult present for at least 7 d.

^c Nests that had signs of disturbed nest material or had evidence of tossed or damaged eggs attributable to house wren competition.

^d Nests with an unknown fate or failed due to disease.

^a Mean values were calculated based on the mean measurements per nest for all nests with eggs or nestlings present during the entire study period from 2000 to 2002.

^b Mean was significantly different from the Fort Custer reference population (Mann–Whitney U, p < .05).

^a Significantly different from reference location (Student's t-test, p < 0.05).

^b NA, not available.

^a TEQs based on World Health Organization toxic equivalence factors (van den Berg et al., 1998).

^b Mean is significantly greater than at the FC reference area (Student's t-test, p < 0.05).

^a NA, not available.