Body Mass and Body Condition Variation of Mallards (Anas platyrhynchos) Within and Among Winters Within the Lower Mississippi Alluvial Valley
Bibliographic record
Abstract
Most North American waterfowl overwinter in southern North America before migrating back to breeding grounds in the northern US and Canada. These species face the challenge of needing to maintain or increase their body mass during an environmentally difficult winter period. Successful body mass maintenance during the winter period has major ramifications not only for their winter survival but for their fitness across the entire year. Recent research in Europe and the western United States suggests that the body mass of mallards (Anas platyrhynchos) has increased from the late 1960s to early 2000s. However, the factors responsible for increases in mallard body mass remain unknown. Because research has shown that mallard body mass and condition is directly proportional to energy acquired across the landscape, conservation agencies attempt to provide high-energy habitat such as woody wetlands, herbaceous wetlands, and open water areas for waterfowl to feed, rest, and complete other important life-cycle activities. Additionally, managers have tried to increase the amount of flooded agricultural grain across the landscape, as crops like rice can provide waterfowl with a source of high-energy food, especially in important overwintering waterfowl areas such as the Lower Mississippi Alluvial Valley (LMAV). However, long-term trends in mallard body mass, as well as the relationship between body condition of mallards and landscape composition has yet to be assessed in the LMAV. To assess mallard body mass over time in the LMAV, we collected measurements from hunter-harvested mallards across the LMAV of Arkansas and Mississippi during duck hunting seasons from 1979-2021. We measured body mass, wing length, and aged and sexed each bird. We then developed four age-sex linear mixed effects models (LMM) analyzing changes in body mass across years. We also analyzed body mass within a winter period across the day of duck season, as well as in relation to cumulative rainfall, river flooding, and a weather severity index (WSI). We determined that mallard body mass has increased within the LMAV from 1979-2021. Within years, body mass generally decreased over the course of the hunting season. Mallard body mass generally increased when rainfall and river flooding increased. However, there was generally no relationship with mallard body mass and WSI. Using Arkansas mallard measurements from duck hunting seasons 2019-2020 and 2020-2021, we calculated body condition indices (BCI) for each bird using the residuals from a mass by wing length regression for each age-sex class. We then used an LMM to analyze changes in mallard BCI in relation to landscape variables known to influence mallard body mass or BCI within a 30-km radius of each harvest site. Landscape variables included proportion of water cover, rice, soybeans, woody wetlands, herbaceous wetlands, open water areas, and areas of human disturbance. We found that mallards with high BCI came from areas with higher proportions of water cover, woody wetlands, and open water. However, mallards with lower BCI came from areas with higher proportions of herbaceous wetlands and human disturbance. We suggest managers restore, protect, and increase food resource availability in wetlands including bottomland hardwood forests.
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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 | 0.002 | 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 | 0.003 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".