Data from: Multi-decadal changes in co-occurrence of migrating landbirds are associated with species-specific changes in phenology and abundance

Human-induced changes to the climate and environment have precipitated
dramatic declines in abundance and shifts in plant and animal phenologies.
These changes have been especially pronounced for migratory species that
rely on numerous geographic locations throughout the year. Migratory bird
species are notable in the number of species that have experienced both
declines in abundance and shifts in phenology over the past 50 years,
although the magnitude and direction of changes vary considerably across
species. The community-level impacts of species declines and phenological
shifts have been explored in stationary communities, but we know little
about the effects of these changes on species relationships during
migration seasons when species may interact in ways that influence their
route, timing, or success of the journey (e.g., through competition or
access to information about resources). Therefore, we assessed the extent
to which co-migrating bird communities have changed over time, and whether
changes in species co-occurrence are associated with changes in abundance
or shifts in migration timing. We used over 700,000 records of birds
captured at five long-term migration monitoring stations in eastern North
America and found that pairwise species co-occurrences have changed by as
much as 40 % over the past 50 years. Changes in co-occurrence were
consistently associated with species-specific changes in phenology and
sometimes associated with changes in abundance. Overall, stopover
communities at three sites have significantly changed over the past few
decades. Numerous and dramatic changes in co-occurrence could be affecting
the types and frequencies of interspecific interactions like competition
and the exchange of social information, transforming the journeys of
migratory birds in innumerable ways that could be altering their timing,
energy, and safety.