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.