Mortality causes in the widespread ibis and spoonbill genera Threskiornis, Plegadis and Platalea: a global review

Context Worldwide, many waterbird species are in decline and are now internationally and nationally threatened. Understanding the causes and rates of mortality for species of concern is critical for effective conservation management. Aim We aim to improve understanding of mortality causes and rates, and highlight gaps in knowledge for ibis and spoonbill species in three genera of the Threskiornithidae family (Threskiornis, Plegadis and Platalea). These genera are widely distributed, frequently prioritised for conservation actions worldwide, and are the only ibis and spoonbill genera in the Oceania region. This is the first global review of mortality for these taxa. Methods We extracted and synthesised mortality data from the international literature for 13 Threskiornithidae species, including mortality causes and rates. Key results Fourteen mortality causes were documented. In decreasing frequency, these were: predation, unknown cause, exposure to weather, water level change, other specified death, human disturbance, human hunting, abandonment, toxins, pathogens and parasites, starvation, competition, collision or entanglement with human structures, and long-distance movement. Few studies provided both mortality causes and rates. Most focused on eggs and chicks, and there was a distinct gap in knowledge for post-fledgling, immature and adult life stages. Conclusions Substantial discrepancies in knowledge among species exist, with a lack of data for endangered species of particular concern. Implications Such knowledge gaps limit the ability of conservation managers to understand and predict the effects of management on populations. New data are required to accurately predict species trajectories and inform management decisions tailored to support species persistence.