Estimating the Abundance of Andean Ibis (Theristicus branickii) in the High Andes of Northern Ecuador

Abstract

The Andean Ibis (Theristicus branickii) is discontinuously distributed in western South America from Ecuador to northern Chile. In Ecuador, it inhabits high elevations (>3,700 m) where it is classified as critically endangered because of its low population number caused by hunting and habitat loss. However, the population size of Andean Ibis in Ecuador is unknown, hindering the implementation of conservation actions. We performed a survey to estimate the abundance of Andean Ibis in the Ecuadorian Andes. In February 2016, and January 2017 and 2018, we conducted 11 point counts. Point counts were located in two provinces, each point count had nine 30-min visits. We recorded Andean Ibis in eight point counts, all in the Province of Napo. Detectability was explained by the amount of nontree vegetation cover and terrain slope, whereas abundance corresponded to gross primary productivity, annual mean temperature, and annual precipitation. We estimated there were 85 (95% credible interval [CI]: 63–117), 94 (95% CI: 32–125), and 134 (95% CI = 77–210) individuals of Andean Ibis in 2016, 2017, and 2018, respectively. The fact that abundance increased in the past 3 years could be explained by an increase in gross primary productivity. We suggest continuing population monitoring and adopting the sampling protocol and data analysis methods presented here as a baseline to better understand the spatiotemporal variation in abundance.