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.

This dataset has two spreadsheets:

Broods data: one brood per row. Includes spatiotemporal and nest content information.
Marques-Santos_Dingemanse_JAV_broods_dryad.csv

Nestling data: one nestling per row. Includes nestling mass, spatiotemporal information, brood, and parental identification.
Marques-Santos_Dingemanse_JAV_nestlingmass_dryad.csv

Data description:

FirstEggDay
On which day of the year (starting April 1 as day 1) the first egg of the clutch was laid.

LayingGap
The number of days during laying where no egg was laid.

ClutchSize
The total number of eggs laid during the focal breeding attempt.

Hatched
Whether the clutch has hatched at least one egg; 0 = no eggs hatched.

HatchDay
On which day of the year (starting April 1 as day 1) the first egg of the clutch hatched.

NumberHatched
The number of eggs that hatched.

Plot
Plot identity. Nest box plot-specific unique identifier.

BroodYear
Year identity. In which year the clutch was laid.

MBirdID
Male bird identity. Individual-specific unique identifier.

FBirdID
Female bird identity. Individual-specific unique identifier.

Fledged
Whether the clutch has fledged. When at least half of the remaining young at age 14 has left the box. 0 = no chicks fledged.

NumberFledged
The number of fledglings produced during the focal breeding attempt.

BroodID
Brood identity. The brood-specific unique identifier associated with each nest attempt.

Day14BodyMass
Nestling mass (g) at age 14 days.

NA
Missing values (applicable to multiple variables listed above).