Local weather can influence the growth and development of young birds, either indirectly, by modifying prey availability, or directly, by affecting energetic trade‐offs. Such effects can have lasting implications for life history traits, but the nature of these effects may vary with the developmental stage of the birds, and over timescales from days to weeks. We examined the interactive effects of temperature, rainfall and wind speed on the mass of nestling and fledgling Barn Swallows Hirundo rustica, both on the day of capture and averaging weather across the time since hatching. At the daily timescale, nestling mass was negatively correlated with temperature, but the strength of this association depended on the level of rainfall and wind speed; nestlings were typically heavier on dry or windy days, and the negative effect of temperature was strongest under calm or wet conditions. At the early lifetime timescale (i.e. from hatching to post‐fledging), nestling mass was negatively correlated with temperature at low wind speed. Fledgling body mass was less sensitive to weather; the only weather effects evident were a negative correlation with temperature at the daily scale under high rainfall that became slightly positive under low rainfall. These changes are consistent with weather effects on availability and distribution of insects within the landscape (e.g. causing high concentrations of flying insects), and with the effects of weather variation on nest microclimate. These results together demonstrate the impacts of weather on chick growth, over immediate (daily) and longer term (nestling/fledgling lifetime) timescales. This shows that sensitivity to local weather conditions varies across the early lifetime of young birds (nestling‐fledgling stages) and illustrates the mechanisms by which larger scale (climate) variations influence the body condition of individuals.

For details of colleciton see Facey et al. 2020 https://doi.org/10.1111/ibi.12824

Headings "Female" and "Chick" (here referring to both nestling and fledgling, see under “Groups) refer to identities of individuals derived from ring/band numbers.

Chick = 8-12 days old

Fledgling = 20+ days

Attempt – breeding attempt, second breeding attempt was considered to be any breeding attempt by the same female that followed a successful first breeding attempt.

Brood Size – maximum number of chicks recorded in the nest

Age – hatching to “Day”

Time – hour during which individuals was handled/weighed (24 hour clock)

Day – day of handling/weighed, where day 1 = 1^st April

Mass – weighed to the nearest 0.1 g using an electronic balance (Satrue SA-500 http://www.satrue.com.tw/dp2.htm).

Weather data

see Facey et al. 2020  https://doi.org/10.1111/ibi.12824 for details on the origins and handling of weather data.

Temperature (^oC) - mean of the daily maximum and daily minimum values

Wind speed (km/h) – daily mean

Rainfall (mm) – total of daily totals.

These data related to the age and mass (see below) of 248 nestling (8–12 days old) Barn Swallows Hirundo rustica, and 75 fledglings (20+ days),  and the weather conditions on the day of handling and over their lifetime.

Data needs to be run as two subsets of “Chicks” and “Fledglings” (see under “Group” heading)  

The dataset contains no missing values.