Multiple stressors and reproductive success of tree swallows: Perfluoroalkyl acids, chemical mixtures, and ecological factors
Bibliographic record
Abstract
Currently there is limited understanding of reproductive effects of perfluoroalkyl acids (PFAAs), especially long-chain perfluorocarboxylic acids (LC-PFCAs; C 9–21 ), in wildlife. Potential reproductive changes in tree swallows ( Tachycineta bicolor ) were evaluated relative to accumulated PFAAs, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (OCPs) and mercury (Hg) in birds nesting ≤250 m downstream of an urban wastewater treatment plant (WWTP) outflow or at a nearby reference site. Near the WWTP outflow, swallows accumulated higher concentrations of perfluorooctane sulfonic acid (PFOS) and LC-PFCAs, C 10,12–14 , and experienced earlier clutch initiation (2019, 2022), longer incubation periods and poorer fledging success in 2022. Egg LC-PFCAs, C 10–15 , PFOS, and perfluorodecane sulfonic acid (PFDS) concentrations correlated with delayed clutch initiation, longer incubation periods, poorer hatching and/or fledging success. Nestling PFOS and the LC-PFCAs, C 10,12,13, were correlated with reduced overall reproductive success and fledging success; fledging success was likely co-influenced by PFAAs, other contaminants, and low temperatures probably limiting prey availability (2022). While the chicks' measured contaminant concentrations involved a smaller proportion of sum (∑) PFAAs (6 %) than ∑PCBs (41 %), ∑PBDEs (14 %), ∑OCPs (20 %), or total Hg (19 %), nonetheless the combination of LC-PFCAs, C 10 – 12 , PFOS, and perfluorooctanoic acid (PFOA) (15 %), had comparable effects as PCBs (24 %) and PBDEs (17 %) on fledging success. Chick burdens of PCBs (20 %) and PBDEs (14 %), but not PFAAs, significantly explained variation in overall reproductive success. Our findings suggest that PFAAs, including LC-PFCAs, can pose reproductive risks for wild birds that are potentially comparable to those of legacy contaminants. • WWTP birds: higher PFAAs, lost early reproductive advantages, poor fledging success • Egg PFAA concentrations associated with longer incubation periods • Nestling PFOS and LC-PFCAs negatively associated with fledging success • Nestling PFAAs, PCBs, PBDEs similarly influenced fledging success of swallows • Overall reproductive success influenced by PCBs and PBDEs
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".