Multiple long-term, landscape-scale datasets reveal intraspecific spatial variation in temporal trends for bird species

Quantifying temporal changes in species occurrence has been a key part of
ecology since its inception. We quantified multi-decadal site occupancy
trajectories for 18 bird species in four independent long-term,
large-scale studies (571 sites, ~ 1000 km latitude) in Australia. We found
evidence of a year x long-term study interaction in the best-fitting
models for 14 of the 18 species analysed, with differences in the temporal
trajectories of the same species in multiple studies consistent with
non-stationarity. Non-stationarity patterns in occupancy were not related
to the distance from a species niche centroid; species in locations
further from their niche centroid did not demonstrate differing temporal
trajectories to those closer to their niche centroid. Further, temporal
trajectories of species were not associated with climatic values for each
study relative to their niche. Our findings demonstrate the need for
multiple long-term studies across a species range, especially when
tailoring conservation decisions for populations.