Bird dataset
Bird abundance data was obtained from eBird, which is an online
repository based on amateurs’ records. Observations are reviewed by
experts and are then aggregated to produce abundance estimates (Sullivan
et al. , 2009). We compiled all records falling within continental
United States including Alaska, and excluded those i) with
georeferencing errors, ii) not identified to the species level, iii)
without abundance information available. We used a second filtering
process to further homogenize the quality of observations. First, to
reduce variation in birds’ detectability, we only kept records with less
than 5 hours of observation, less than 5 km of traveled distance, and 10
or fewer observers (as recommended in Strimas-Mackey et al., 2020).
Second, we only considered data ranging from 1969 to 2016, which is the
greatest recording effort period (Appendix S2) for which we have
environmental data available (see below). Third, we used BirdLife
species distribution maps (BirdLife International and Handbook of the
Birds of the World, 2016) to exclude sightings of birds recorded outside
their home and breeding areas (for example, in migratory routes).
Fourth, we only kept those species that presented at least 150 records
to minimize type I error in QR (Cade et al. , 2005). Lastly, we
estimated relative abundances as the species’ local abundance divided by
the minutes of observation (i.e., abundance weighted by sample effort)
and excluded outlier records (i.e., relative abundance values 100 times
greater than the observed value in the 75th quartile). Our final dataset
contained 49,835 records belonging to 114 bird species (an average of
437 records by species, with a minimum of 152 records for the speciesPasserculus sandwichensis and a maximum of 1,758 records for the
species Zenaida macroura ).