Abstract
Increasingly harsh and unpredictable climate regimes are affecting animal populations around the world as climate change advances. One relatively unexplored aspect of species vulnerability to climate change is whether and to what extent responses to environmental stressors might be mitigated by variation in group size in social species. We used a 15-year dataset for a cooperatively-breeding bird, the southern pied babbler Turdoides bicolor, to determine the impact of temperature, rainfall, and group size on body mass change and interannual survival in both juveniles and adults. Hot and dry conditions were associated with reduced juvenile growth, mass loss in adults, and compromised survival between years in both juveniles (−86%) and adults (−60%). Individuals across all group sizes experienced similar effects of climatic conditions. Larger group sizes may not buffer individual group members against the impacts of hot and dry conditions, which are expected to increase in frequency and severity in future.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Author contacts: ARB (abourne.uct{at}gmail.com), SJC (susie.j.c{at}gmail.com), CNS (cns26{at}cam.ac.uk), ARR (amanda.ridley{at}uwa.edu.au)
Statement of authorship ARR, SJC, ARB, and CNS conceived the study and secured funding. ARR started habituation of the study animals and collection of life history data in 2003 and has maintained it ever since; this was central to making the study possible. ARB undertook all fieldwork from 2016 onwards. ARB and ARR analysed the data. ARB drafted the manuscript. All authors contributed substantially to revisions, and gave final approval for publication.
Data accessibility statement The data underlying all analyses presented here will be archived at the University of Cape Town’s open-access institutional data respository, ZivaHub (a figshare platform), where it will be publicly available.
- Brood size
- Number of nestlings per brood
- G.SizeBrood
- Number of adults in the natal group at initiation of incubation
- G.Size90
- Average number of adults in the natal group between fledge and nutritional independence at 90 days of age
- G.SizeBrSeas
- Average number of adults in the natal group over the breeding season
- Mass11
- Nestling body mass (0.1 g) collected 11 days after hatching
- Mass90
- (Average) body mass data (0.1 g) collected from 90 (± 15) day-old birds
- ΔMb.Juv
- Change in juvenile body mass (g), calculated as Mass90 − Mass11
- MassOct
- (Average) body mass data (0.1 g) collected from adults at the beginning of the breeding season (September and October)
- MassMar
- (Average) body data (0.1 g) collected from adults at the end of the breeding season (February and March)
- ΔMb.Adults
- Change in adult body mass (g), calculated as MassMar – MassOct
- Mean TmaxBrood
- Average daily maximum temperatures between hatching and fledging
- Mean Tmax90
- Average daily maximum temperatures between fledging and nutritional independence at 90 days of age
- Mean TmaxBrSeas
- Average daily maximum temperatures between the start (September) and the end (March) of the breeding season
- Rain60
- Total rainfall in the 60 days prior to initiation of incubation at the nest from which each individual fledged
- Rain90
- Total rainfall between fledging and nutritional independence at 90 days of age
- RainBrSeas
- Total rainfall between the start (September) and the end (March) of the breeding season
- DroughtBrSeas
- Occurrence of a meteorological drought (rainfall < 135.75 mm) within the breeding season