Weather effects on nestling survival of great tits vary according to the developmental stage

Organisms change breeding investments as a function of the environment,
thereby maximizing reproductive success. Climate change studies of avian
life-history have long focused on plasticity of laying dates and clutch
sizes in response to weather conditions prior to clutch initiation. By
contrast, effects of unpredictable weather events occurring after initial
reproductive decisions are made have largely been ignored, despite
becoming increasingly important with ongoing climate change. We studied
the detrimental effects of fluctuations in temperature and precipitation
during various nesting phases of great tits (Parus major), identifying the
developmental age windows where weather fluctuations affected hatching,
nestling mass and fledging success. We used a longitudinal (8-year)
dataset of great tits breeding in next boxes in southern Germany and
applied a recently introduced explorative approach that does not require a
priori assumptions on the time windows (range of ages) over which weather
may affect reproductive parameters. Lower temperatures and higher
precipitation during the nestling phase negatively affected nestling mass
and survival: nestlings between the ages 6-9 days were most susceptible to
this form of variation in weather. Effects of weather did not differ
between years, i.e., there was no evidence for ‘good’ versus ‘bad’ years.
Future research should focus on the mechanisms underpinning effects of
weather on nestling growth and survival in other populations and consider
whether age-dependent weather consequences occur in a wide variety of
taxa, as specific developmental stages may serve as weak spots in a
scenario of increasing recurrence of weather extremes.