Reproductive life-history variation in a secondary cavity-nester across an elevational gradient in Andean temperate ecosystems
Bibliographic record
Abstract
Avian reproductive strategies have been hypothesized to vary with elevation. Shorter breeding seasons due to harsh environmental conditions, and potentially higher predation risks, may reduce clutch sizes at higher elevations, which in some species leads to increased parental care and offspring survival. However, this phenotypically plastic and potentially adaptive response has been documented only in a handful of species in the Northern Hemisphere. For the first time in a southern temperate ecosystem, we studied whether the breeding strategy of a secondary cavity-nester varied along an elevational gradient in Andean temperate forests, Chile. We installed 240 nest-boxes at 260–1,115 m elevation and monitored the breeding activity of 162 nests of Thorn-tailed Rayaditos (Aphrastura spinicauda) over 2 seasons (2010–2012). We included 50 nests from a third season only for recording clutch size and nestlings per clutch. As predicted, the breeding season was shorter in highland forests than in lower elevations, by 28% and 55% over the 2 successive seasons. Although timing of egg laying (1 egg every second day) and incubation period (average = 15 days) did not vary with elevation, we found smaller clutch sizes (average = 4.1 vs. 4.5) and fewer nestlings per clutch (average = 3.5 vs. 4.2) at higher elevations. The extent of parental care, expressed as the duration of the nestling period, was slightly but significantly greater in highland than in lowland forests (22.2 vs. 21.6 days). Despite the longer nestling period at higher elevations, nesting success was lower at high elevations, mainly because of nest predation. Our findings suggest that Thorn-tailed Rayaditos may change to a slower reproductive strategy along elevational gradients. Yet these changes do not appear to compensate for the increased predation rates at higher elevations, calling into question the potential adaptive significance of this strategy.
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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 | 0.000 |
| 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".