Assessing population size and structure for Andean Condor Vultur gryphus in Bolivia using a photographic ‘capture‐recapture’ method

Abstract

The Andean Condor Vultur gryphus is a globally threatened and declining species. Problems of surveying Andean Condor populations using traditional survey methods are particularly acute in Bolivia, largely because only few roosts are known there. However, similar to other vulture species, Andean Condors aggregate at animal carcasses, and are individually recognizable due to unique morphological characteristics (size and shape of male crests and pattern of wing coloration). This provided us with an opportunity to use a capture‐recapture (‘sighting‐resighting’) modelling framework to estimate the size and structure of an Andean Condor population in Bolivia using photographs of individuals taken at observer‐established feeding stations. Between July and December 2014, 28 feeding stations were established in five different zones throughout the eastern Andean region of Bolivia, where perched and flying Andean Condors were photographed. Between one and 57 (mean = 20.2 ± 14.6 sd) Andean Condors were recorded visiting each feeding station and we were able to identify 456 different individuals, comprising 134 adult males, 40 sub‐adult males, 79 juvenile males, 80 adult females, 30 sub‐adult females and 93 juvenile females. Open population capture‐recapture models produced population estimates ranging from 52 ± 14 (se) individuals to 678 ± 269 individuals across the five zones, giving a total of 1388 ± 413 sd individuals, which is roughly 20% of the estimated Andean Condor global population. Future trials of this method need to consider explicitly knowledge of Andean Condor movements and home‐ranges, habitat preferences when selecting suitable sites as feeding stations, juvenile movements and other behaviours. Sighting‐resighting methods have considerable potential to increase the accuracy of surveys of Andean Condors and other bird species with unique individual morphological characteristics.

Spatial and temporal patterns in age structure of Golden Eagles wintering in eastern North America

“…However, in recent years several camera‐trapping studies have focused on birds (Luo et al , Roncol et al ). Together with several other recent studies (e.g., Jachowski et al , Vukovich et al, , Méndez et al , Watson et al ), our study shows how using trail cameras to study birds that can be brought to a fixed location (i.e., a bait site) can result in important ecological insight.…”

Andean and California condors possess dissimilar genetic composition but exhibit similar demographic histories

“…In 1970, the species was declared “Endangered” (USFWS, 1970), and three decades later was listed as globally “Near Threatened” by the International Union for Conservation of Nature (BirdLife International, 2017) and is currently recommended to be listed as “Vulnerable” (Plaza & Lambertucci, 2020). At the local level, the species is “Critically Endangered” in its northern distribution: Condors are functionally extirpated in Venezuela, <150 individuals inhabit Colombia, ~100 individuals inhabit at Ecuador, ~250 to 1,000 remain in Bolivia, and ~300 to 2,500 are estimated to occupy Peru (Méndez et al., 2019; Naveda‐Rodríguez et al., 2016; Piana & Angulo, 2015). In the southern part of its distributional range, Andean condors were extirpated from the steppe and the Atlantic coasts 100 years ago (Conway, 2005), but holdout in the high Andes (Lambertucci et al., 2018; Perrig et al., 2017, 2020).…”

Effect of nest composition, experience and nest quality on nest-building behaviour in the Bonelli’s Eagle

“…Capture-recapture methods involving identification based on photographs is recognized as a reliable method to monitor wildlife populations and assess ecological aspects such as population size and structure, survival, site-fidelity, occupancy, lifetime reproductive success and other variables 61 – 65 . Following previous studies on vultures 66 and raptors, including Bonelli’s Eagle 61 , 67 , 68 , we took photographs of individual Bonelli’s Eagles using camera traps placed on rock perches 68 and a digital camera mounted on a digiscoping adaptor attached to a spotting scope in a hide 66 . Territorial Bonelli’s Eagles could be recognized from these photographs of perched individuals (Fig.…”