Contrasting sensitivity of nestling and fledgling Barn Swallow Hirundo rustica body mass to local weather conditions

Abstract

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 effets 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 pre‐fledging), nestling mass was negatively correlated with temperature at low wind speed. Fledgling body mass was less sensitive to weather; the only weather effect evident was 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 the 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.

Minor interspecies differences in breeding phenology and productivity between two co-occurring aerial insectivores

“…Recent studies of Tree Swallows have found a decrease in nestling body mass with an increase in mean rainfall during the nestling period (Cox et al 2019) (Facey et al 2020). Overall, we found that Tree Swallows and Barn Swallows showed similar responses to local weather conditions in terms of breeding phenology over the four years of our study.…”

“…We obtained weather data from Environment and Climate Change Canada (Government of Canada 2019) for all four years (2013-2016) from a Vancouver weather station (YVR Airport, 49°11'42.000" N, 123°10'55.000" W, elevation 4.30 m). We used data for average daily temperature (°C), average daily precipitation (mm), and average daily wind speed (km/h) as variables to represent local weather (Cox et al 2019, Facey et al 2020. We calculated averages for (1) the pre-laying period, either 2 or 4 wk (to account for the nest-building period and arrival on breeding grounds) before the first egg date for each species in each year, and (2) for the month of June, which coincided with the main chick-rearing period for first broods in both species.…”

The Effects of Weather on Avian Growth and Implications for Adaptation to Climate Change

“…Lastly, the interaction of different weather effects may change our predictions of future change because interactions among weather variables or other changing variables could enhance or ameliorate negative effects. For example, in a study of barn swallows Hirundo rustica, nestling mass between age 8-12 days is negatively associated with increasing temperatures, and this effect is stronger during heavier rainfall, but weaker during high wind speeds (Facey et al, 2020).…”

The interactive effect of ambient temperature and brood size manipulation on nestling body mass in blue tits: an exploratory analysis of a long-term study

“…both positive and negative relationships can occur, depending on species and/or population) and context-dependent (i.e. differing between environments) [ 21 , 24 – 27 ]. One explanation of this variability may result from the fact that negative effects of adverse weather can be moderated by adjustments in parental care strategies [ 24 , 28 , 29 ].…”