Polygyny, Male Parental Care, and Sex Ratio in Song Sparrows: an Experimental Study
Bibliographic record
Abstract
AnsTP,•CT.--Species that are typically monogamous, but occasionally show polygyny, allow tests of several hypotheses about mating systems.We describe seven cases of natural polygyny observed during a 5-yr study of the Song Sparrow (Melospiza melodia).We also report on an experiment designed to test whether or not altering sex ratios causes polygyny and to measure some costs associated with polygyny in the Song Sparrow.Natural polygyny occurred in two circumstances: when males died during the breeding season and when the breeding population contained an excess of females.Most bigamous male Song Sparrows fed only the young of their primary females, but unaided secondary females were able to raise some young to independence.In 1979, we removed nine male Song Sparrows soon after their first-bmod young hatched.Four of the nine widowed females subsequently formed polygynous associations with already mated males, compared to a natural polygyny rate of 3%.In one case, a male paired with three females.Only one of the widowed females received aid from her new male in feeding the young in her first brood.Young of unaided females grew more slowly and died more often in the nest than young of control females, and only half as many of them survived to independence.Unaided females fed their young twice as often as did control females.Removed males were replaced either by neighbors or by nonterritorial males.The latter group were also removed until all replacements were neighbors.When females remated with these replacements, 8 of their 9 previous mates were released, and 2 of them regained their previous territories.Neither was known to have fed the second-brood young of its regained mate.Foster fathers showed little "altruistic" behavior.Our results demonstrate that biased sex ratios are a proximate cause of polygyny in the Song Sparrow.We suggest that Song Sparrows are usually monogamous because males with high quality territories outnumber females at the onset of the breeding season.When females are not in short supply, polygyny occurs.
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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 | 0.001 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".