Weather and nest cavity characteristics influence fecundity in mountain chickadees

• Published in: PeerJ (San Francisco, CA) Vol. 10; p. e14327
• Main Authors: Norris, Andrea R, Martin, Kathy, Cockle, Kristina L
• Format: Journal Article
• Language: English
• Published: United States PeerJ. Ltd 11.11.2022; PeerJ, Inc; PeerJ Inc
• Subjects: Analysis; Animal Behavior; Animals; Bark beetles; Birds; British Columbia; Brood size; Cavities; Cavity nesting; Cavity size; Climate; Climate change; Climate Change Biology; Climatic changes; Climatic conditions; Clutch size; Competition; Coniferous forests; Conspecifics; Cumulative effects; Dendroctonus ponderosae; Ecology; Eggs; Environmental changes; Environmental conditions; Fecundity; Fertility; Food; Food availability; Foraging behavior; Forests; Hypotheses; Laying date; Nests; Pest outbreaks; Phenology; Plant Breeding; Population Biology; Predation; Predators; Rain; Seasons; Songbirds; Storms; Survival; Weather; Zoology; British Columbia; Canada; Cavity size; Brood size; Climate; Cumulative effects; Prey availability; Nest survival; Clutch size; Poecile gambeli; Mountain Chickadee; Laying date
• ISSN: 2167-8359; 2167-8359
• DOI: 10.7717/peerj.14327

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 ( ), 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; ), and safer (smaller, higher) cavities. 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 ( ) 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. 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 ( 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.