Reproductive and endocrine health of Tree Swallows (Tachycineta bicolor) exposed to historical and current-use flame retardant chemicals in wastewater treatment plant effluent
Bibliographic record
Abstract
Flame retardants (FRs) are ubiquitous chemicals, some of which may persist in the environment and bioaccumulate in wildlife. Recent laboratory studies on American kestrels (Falco sparverius) have demonstrated that exposure to these chemicals may be linked to reproductive and other health problems in animals, but little is known about these effects in free-ranging avian species. The overall aim of this study was to examine the occurrence and possible reproductive and endocrine effects of historical and current-use FR chemicals in free-ranging birds using the tree swallow (Tachycineta bicolor) as a model. Breeding colonies of tree swallows were established at one reference site and two wastewater treatment plant (WWTP) sites; with the effluent from one WWTP (i.e., the WWTP near Kitchener, Ontario: KWWTP) being more highly contaminated with FRs than the other (i.e., near Hamilton, Ontario: WAWWTP). From 2007 to 2010, freshly laid eggs (n = 127) were collected from each nest and analyzed for FR concentrations; these same nests were monitored regularly and reproductive measures were recorded, and the occurrence of endocrine disruption was assessed in a sub-sample of adult tree swallows. Across sites, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 2,2'.4,4',5-pentabromodiphenyl ether (BDE-99), 2,2'4,4',6-pentabromodiphenyl ether (BDE-100), 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153), and 2,2',4,4',5,6'-hexabromodiphenyl ether (BDE-154) were found at the highest concentrations in the tree swallow eggs, with other polybrominated diphenyl ether (PBDE) congeners and FRs being quantified at much lower levels. Tree swallows at the KWWTP site had significantly smaller clutches than those at the WAWWTP site, and egg volume (cm3) was positively correlated with in ovo levels of decabromodiphenylether (BDE-209), hexabromocyclododecane (HBCD), and brominated biphenyl (BB)-101. Hatching, fledging and breeding success of the tree swallows were significantly different among sites although there were no statistically significant associations between these measures and in ovo FR concentrations. Clutch initiation date, predation of eggs and nestlings, female age, and ambient temperatures were also found to significantly differ among sites. Nonparametric regression analysis showed that clutch initiation date and egg predation were the best predictors of breeding success across sites, but not flame retardants at currently measured in ovo concentrations. From 2009 to 2010, fecal samples were collected from breeding adult male and female tree swallows during the phases of courtship/nest construction and incubation; these samples were subsequently analyzed for levels of fecal estradiol (E2), testosterone (T), triidothyronine (T3), and thyroxine (T4) metabolites. In 2011, the enzyme immunoassays (EIAs) were biologically validated for the adult tree swallows using nestling tree swallows as negative controls. For adult female tree swallows, there was a moderately significant increase in fecal T4 metabolite levels with in ovo BDE-209 concentrations. For male birds, there were significant and negative associations between fecal T metabolite levels and in ovo BDE-47 and BDE-153 concentrations. The results of this study indicate that free-ranging passerines may be less reproductively sensitive to the effects of FRs at currently measured in ovo concentrations compared to higher trophic level avian species, and that multiple factors may be influencing the reproductive success of the tree swallows at these particular study sites. However, the results of this study also suggest that tree swallows may be sensitive to current environmental concentrations of flame retardants in terms of endocrine function; further research is warranted.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".