American Black Duck Anas rubripes and Mallard A. platyrhynchos abundance,occurrence of heterospecifi c pairing and wetland use between 1976 and 2003 in Northeastern Nova Scotia, Canada
Bibliographic record
Abstract
Mallard Anas platyrhynchos abundance has increased in eastern North America with a concomitant decline in the number of Black Duck A. rubripes in some parts of their range. It has been speculated that introgressive hybridisation or competitive exclusion have been the mechanisms for the opposing population trajectories of these species. In particular, the prevailing view is that heterospecifi c pairs of male Mallard x female Black Duck are contributing to the hybridisation of the two species, with a combination of Mallard releases and use of urban areas increasing the frequency of these pairings. This paper reports long-term survey data documenting the relative frequency and combination of sexes of mixed pairs from two sites in eastern Canada, and the extent of movement of Mallard into habitat dominated by Black Duck from points of Mallard concentration in Nova Scotia. This study indicates no long-term decline in Black Duck, nor an increase in Mallard, in northeastern Nova Scotia between 1976 and 2003. Heterospecifi c pairs in Nova Scotia were rare and consisted primarily of male Black Duck x female Mallard; heterospecifi c pairings were more common in a St. Lawrence River study area and were mainly of the expected male Mallard x female Black Duck combination. Two clines with respect to heterospecifi c pairing are suggested from these data: (1) an increase in frequency, and (2) a change in male : female composition by species moving from east to west. The occurrence of Mallard appears to be limited to a 1-km to 3-km radius from discrete points of introduction or concentration. Within this radius, Black Duck abundance was low. Outside this area, at a 3-km to 15-km radius, it then increased twofold at Shubenacadie and sevenfold at Goshen. Thus, Mallard releases in this area appear to have only localised effects. This study found no evidence for Mallard or hybrid increases, Black Duck declines, the occurrence of competitive exclusion, or of introgressive hybridisation in Black Duck in northeastern Nova Scotia between 1976 and 2003.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".