Weather and nest cavity characteristics influence fecundity in mountain chickadees
Bibliographic record
Abstract
Background Examining direct and indirect effects on reproduction at multiple scales allows for a broad understanding of species’ resilience to environmental change. We examine how the fecundity of the mountain chickadee ( Poecile gambeli ), a secondary cavity-nesting, insectivorous bird, varied in relation to factors at three scales: regional weather conditions, regional- and site-level food availability, site-level community dynamics, and nest-level cavity characteristics. We hypothesized that earlier laying dates and higher fecundity (clutch size, nest survival, brood size) would be associated with milder climatic conditions, increased food from insect outbreaks, lower densities of conspecifics and nest predators (red squirrel; Tamiasciurus hudsonicus ), and safer (smaller, higher) cavities. Methods We collected data on laying date, clutch size, brood size, nest fate (success/failure), and cavity characteristics from 513 mountain chickadee nests in tree cavities in temperate mixed coniferous-broadleaf forest in interior British Columbia, Canada, from 2000 to 2011. We surveyed annual abundances of mountain chickadees and squirrels using repeated point counts, and mountain pine beetle ( Dendroctonus ponderosae ) and lepidopteran defoliators by monitoring host trees and by using regional-scale aerial overview forest insect survey data. We used weather data (temperature, rain, snow) from a local Environment and Climate Change Canada weather station. We modeled laying date, clutch size, daily nest survival, and brood size as a function of predictors at regional-, site-, and nest-scales. Results and Conclusions Measures of fecundity varied dramatically across years and spatial scales. At the regional (study-wide) scale, chickadees laid earlier and larger first clutches in warmer springs with minimal storms, and daily nest survival (DSR) increased with a 2-year lag in growing season temperature. Despite a doubling of mountain chickadee density that roughly accompanied the outbreaks of mountain pine beetle and lepidopteran defoliators, we found little evidence at the site scale that fecundity was influenced by insect availability, conspecific density, or predator density. At the nest scale, DSR and brood size increased with clutch size but DSR declined with nest cavity size indicating a positive reproductive effect of small-bodied cavity excavators. Double-brooding, rare in chickadees, occurred frequently in 2005 and 2007, coinciding with early breeding, high food availability from insect outbreaks, and warm spring temperatures with 0-1 spring storms. Our results support the idea that fecundity in secondary cavity-nesting species is impacted directly and indirectly by weather, and indirectly through changes in community dynamics ( via cavity resource supply). We stress the importance of adopting holistic, community-level study frameworks to refine our understanding of fecundity in opportunistic and climate-sensitive species in future.
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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 | 0.000 | 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 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".