Data from: Timing and intensity of weather events shape nestling development strategies in three alpine breeding songbirds

Across taxa, offspring size traits are linked to survival
and life-time fitness. Inclement weather can be a major constraint on offspring
growth and parental care. Despite the adaptive benefits of larger offspring, we
have a limited understanding of the effects of severe environmental conditions across
developmental stages and how coping strategies differ among species. We assessed the influence of inclement weather on offspring size and mass
traits within populations of three alpine breeding songbirds in British
Columbia: 1) horned lark (Eremophila alpestris), 2) dark-eyed junco (Junco
hyemalis), and 3) savannah sparrow (Passerculus sandwichensis). Specifically,
we investigated at which stages during early-life development offspring are most
vulnerable to inclement weather and whether thresholds exist in the
developmental response to severe weather events. Across
species, we identified two critical periods that best predicted offspring size:
1) clutch initiation, and 2) the nestling stage. Colder temperatures experienced by
the female during clutch initiation were associated with larger, heavier
offspring in horned larks but smaller offspring for savannah sparrows,
indicating the potential for maternal effects, albeit acting through different
mechanisms. Additionally, horned lark offspring were
resilient to colder average temperatures during the nestling stage but were
vulnerable to extreme cold events and multi-day storms. In contrast, dark-eyed
junco nestlings were robust to storms, but smaller size and mass traits were
associated with lower daily maximum temperatures (i.e., more mild temperature
challenges). We suggest species differences may be linked to life-history
traits, such as: 1) the thermoregulatory benefits of larger body mass in horned
larks, 2) the benefits of greater nest cover to buffer dark-eyed junco against
precipitation events, and 3) delayed clutch initiation for savannah sparrows to
limit exposure to cold storms. We provide evidence for stage-specific impacts
of inclement weather on offspring development with implications for
reproductive success. These results advance our understanding of early-life
resilience to stochastic environments, as we may be able to predict differences
in the vulnerability of alpine species to increasingly variable and severe
weather conditions.