Biological traits of seabirds predict extinction risk and vulnerability to anthropogenic threats

Aim Seabirds are heavily threatened by anthropogenic activities and their
conservation status is deteriorating rapidly. Yet, these pressures are
unlikely to uniformly impact all species. It remains an open question if
seabirds with similar ecological roles are responding similarly to human
pressures. Here we aim to: 1) test whether threatened vs non-threatened
seabirds are separated in trait space; 2) quantify the similarity of
species’ roles (redundancy) per IUCN Red List Category; and 3) identify
traits that render species vulnerable to anthropogenic threats. Location
Global Time period Contemporary Major taxa studied Seabirds Methods We
compile and impute eight traits that relate to species’ vulnerabilities
and ecosystem functioning across 341 seabird species. Using these traits,
we build a mixed-data PCA of species’ trait space. We quantify trait
redundancy using the unique trait combinations (UTCs) approach. Finally,
we employ a SIMPER analysis to identify which traits explain the greatest
difference between threat groups. Results We find seabirds segregate in
trait space based on threat status, indicating anthropogenic impacts are
selectively removing large, long-lived, pelagic surface feeders with
narrow habitat breadths. We further find that threatened species have
higher trait redundancy, while non-threatened species have relatively
limited redundancy. Finally, we find that species with narrow habitat
breadths, fast reproductive speeds, and varied diets are more likely to be
threatened by habitat-modifying processes (e.g., pollution and natural
system modifications); whereas pelagic specialists with slow reproductive
speeds and varied diets are vulnerable to threats that directly impact
survival and fecundity (e.g., invasive species and biological resource
use) and climate change. Species with no threats are non-pelagic
specialists with invertebrate diets and fast reproductive speeds. Main
conclusions Our results suggest both threatened and non-threatened species
contribute unique ecological strategies. Consequently, conserving both
threat groups, but with contrasting approaches may avoid potential changes
in ecosystem functioning and stability.