Data and code from: Climate and species traits give rise to complex phenological dynamics

Climate change has substantially shifted the phenology of organisms. These
shifts vary across species and habitats and are shaped by species natural
history traits and local environmental conditions, yet the relative
importance of these drivers remains unclear. Moreover, climate can have
diverse effects on different aspects of phenology, such as the timing and
duration of activity, but this complexity is rarely captured by commonly
used phenological metrics. We used multidecadal butterfly surveys and
climate data from five montane sites spanning an elevational gradient to
investigate how climate affects different aspects of annual flight period
of 135 butterfly species. Using a hierarchical Bayesian framework, we
modeled annual probability of occurrence distributions for species using
polynomial models that capture changes in abundance, timing, and length of
flight. Spring maximum and minimum temperatures and winter precipitation
were the best predictors of inter-annual variation in phenology. High
winter precipitation, which usually comes in the form of snow, delayed
phenology, while warmer spring maximum temperatures advanced phenology
across elevations. Even modest increases in spring minimum (nighttime)
temperatures caused strong phenological shifts. Climate effects varied
among sites, among species within sites, and even among populations of the
same species across sites, with particularly pronounced variation among
species within a site. Variation in climate effects were slightly better
explained by local climate than by natural history traits. Among natural
history traits, voltinism and overwintering stage were particularly
influential. Importantly, climate influenced different aspects of the
flight period (e.g., timing versus duration) in distinct ways, with both
natural history traits and local climate modulating these responses. Our
findings highlight the often-overlooked importance of winter precipitation
and nighttime temperatures in shaping phenology and demonstrate the value
of considering the entire flight period, rather than distinct aspects
alone, to improve our understanding and predictions of species response to
climate change.