Functional Diversity
To capture the functional diversity of the focus species at each point,
site, and domain, we used the AVONET database (Tobias, 2021) which
provides morphological, geographic, and ecological information about all
bird species. Functional diversity measures from AVONET included bill
length (cm), tail length (cm), wing length (cm), tarsus length (cm),
mass (g), Hand Wing Index (HWI) (which is a measure of wing shape), diet
percentage, range size, and foraging stratum. We identified two
functional diversity metrics for this study: functional richness and
redundancy. We also tabulated species’ abundance and richness at each
NEON survey point. Species richness and functional diversity metrics
were calculated with the dbFD function in the R package ‘FD’
(Villeger et al., 2008; Laliberte and Legendre, 2010; Laliberte,
Legendre, and Shipley, 2014). Functional richness represents the volume
of trait space occupied by species. To estimate the amount of functional
redundancy at each survey location, we calculated community-level
functional redundancy using the ‘adiv’ package in R (Pavoine, 2020;
Pavoine, 2021). Redundancy ranged between 0 and 1, with high values
indicating high levels of overlap in species traits (Pavoine and
Ricotta, 2019). Functional richness gives us the functional breadth of
the avian community, while functional redundancy informs us about the
overlap and similarity of species within a community at each point
location.