Life history traits explain vulnerability of endemic forest birds and predict recovery after predator suppression

Abstract

New Zealand’s native forest bird species with high taxonomic levels of endemism (deep endemics) are more vulnerable to decline than species that arrived and speciated more recently. Here we use national-scale local occupancy data to show that three endemism-linked life-history traits account for greater vulnerability of deep-endemic species in the extant forest avifauna, but also that other, more subtle traits and mechanisms favour rather than hinder endemic persistence. We suggest that these traits together provide a basis for predicting changes in local occupancy following suppression of introduced mammalian predators in different landscapes. Our analyses disentangle the limiting effects of forest area, predation, and food availability for different species. They support understanding that predation by introduced mammals is the primary cause of forest bird declines and limitation today, but suggest that large tracts of native forest are essential for future restoration of endemic forest avifauna, even following suppression of introduced mammalian predators. We predict that with fewer predators (1) deep-endemic species would most successfully and rapidly recover in large tracts of warm forest, (2) scarcity of forest or food would limit recovery in larger-bodied, less mobile species and in mobile cavity-nesters, and (3) interspecific competition would become influential and produce community reassortment.