Effects of weather variation on waterfowl migration: lessons from a
continental-scale generalizable avian movement and energetics model
Abstract
We developed a nonbreeding period continental-scale energetics-based
model of daily waterfowl movement to predict year-specific migration and
overwinter occurrence. The model approximates energy-expensive movements
and energy-gaining stopovers as functions of metabolism and weather, in
terms of temperature and frozen precipitation (i.e., snow). The model is
a Markov process operating at the population level and is parameterized
through a review of literature. We examined model performance against 62
years of non-breeding period daily weather data. The average proportion
of available habitat decreased as weather severity increased, with
mortality decreasing as the proportion of available habitat increased.
The most commonly used nodes during the course of the nonbreeding period
were generally consistent across years, with the most inter-annual
variation present in the overwintering area. Our model revealed that the
distribution of birds on the landscape changed more dramatically when
the variation in daily available habitat was greater. The main routes
for avian migration in North America were predicted by our simulations:
the Eastern, Central, and Western flyways. Our model predicted an
average of 77.4% survivorship for the nonbreeding period across all
years (range = 76.4 – 78.4%), with lowest survivorship during the
fall, intermediate survivorship in the winter, and greatest survivorship
in the spring. We provide the parameters necessary for exploration
within and among other taxa to leverage the generalizability of this
migration model to a broader expanse of bird species, and across a range
of climate change and land use/land cover change scenarios.