Decoupled spatiotemporal patterns of avian taxonomic and functional diversity

Authors: Marta A. Jarzyna and James H. Stagge

Year: 2023

Publication: Current Biology

Publication Link:

Abstract: Each year, seasonal bird migration leads to an immense redistribution of species occurrence and abundances,
1–3 with pervasive, though unclear, consequences for patterns of multi-faceted avian diversity.
Here, we uncover stark disparities in spatiotemporal variation between avian taxonomic diversity (TD) and
functional diversity (FD) across the continental US. We show that the seasonality of species richness expectedly
3 follows a latitudinal gradient, whereas seasonality of FD instead manifests a distinct east-west gradient.
In the eastern US, the temporal patterns of TD and FD are diametrically opposed. In winter, functional richness
is highest despite seasonal species loss, and the remaining most abundant species are amassed in
fewer regions of the functional space relative to the rest of the year, likely reflecting decreased resource availability.
In contrast, temporal signatures for TD and FD are more congruent in the western US. There, both species
and functional richness peak during the breeding season, and species’ abundances are more regularly
distributed and widely spread across the functional space than during winter. Our results suggest that migratory
birds in the western US disproportionately contribute to avian FD by possessing more unique trait characteristics
than resident birds,4,5 while the primary contribution of migrants in the eastern US is through
increasing the regularity of abundances within the functional space relative to the rest of the year. We anticipate
that the uncovered complexity of spatiotemporal associations among measures of avian diversity will
be the catalyst for adopting an explicitly temporal framework for multi-faceted biodiversity analysis.

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