Food supplementation leads to bottom‐up and top‐down food–host–parasite interactions
Bibliographic record
Abstract
1. Food-prey-predator interactions may involve both 'bottom-up' and 'top-down' processes. Conventionally, food-host-parasite interactions have been seen as governed solely from the 'bottom-up', i.e. well-fed hosts can better resist parasites and so suffer less parasitism. Recent studies on diverse endo- and ecto-parasites increasingly highlight that well-fed hosts provide parasites with a better resource base, and so may be more likely to be parasitized. 2. Brood parasites exploit host parental behaviour by laying their eggs in others' nests. The brown-headed cowbird (Molothrus ater) is a North American brood parasite that exploits over 100 host species. 3. We conducted a food addition experiment on song sparrows (Melospiza melodia), a frequently parasitized cowbird host, near Victoria, BC, Canada. We expected results consistent with conventional 'bottom-up' effects because we previously found that food supplemented sparrows better eluded nest predation, and we thus also expected them to be better at eluding cowbird parasitism. 4. Here, we report results to the contrary. Food supplemented sparrows were parasitized as often as non-food supplemented sparrows, were multiply parasitized significantly more often, and suffered significantly more parasitism-induced egg loss. Our results suggest cowbirds preferentially parasitized better fed hosts and cowbirds benefited from doing so as food supplemented sparrows fledged significantly more cowbird young per multiply parasitized nest. The pattern of egg loss also accorded with recent evidence indicating that cowbirds may remove just the right number of host eggs to maximize provisioning of the cowbird nestling. 5. Our work suggests that brood parasitism in vertebrates involves both 'top-down' and 'bottom-up' processes consistent with the growing number of studies showing that food-host-parasite interactions are more complex than previously thought. One of the conservation implications of our results is that greater food availability may not provide hosts a respite from brood parasitism, but is, nonetheless, beneficial overall.
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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 | 0.000 |
| 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 | 0.001 |
| 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".