240 I. F. Valencia et al.


Valley (Renjifo et al., 2002). These areas include some of the most transformed and least protected ecosystems in Colombia (Forero-Medina & Joppa, 2010; González-Caro & Vásquez, 2018). Habitat destruction across the species’ range, and hunting, are the greatest threats to the blue- billed curassow and have caused dramatic declines in its populations (Renjifo et al., 2002; Melo-Vasquez et al., 2008). Although it is currently categorized as Critically Endangered on the IUCN Red List (BirdLife International, 2018), there have been no robust assessments of the viabil- ity of its remnant populations or of the potential impacts of possible conservation actions. Given the reduction of its range, it is essential to understand which populations could persist over time and the relative value of alternative conservation strategies. This is the case not only for the blue-billed curassow but also for other endemic and keystone species in the tropics for which information on population viability is not available. In this study we used population viability analysis to


evaluate the viability of the C. alberti population located in the municipality of Yondó, Antioquia, over a 100-year timeframe, and to compare the effectiveness of the conser- vation actions that could be implemented. For this we col- lected field data using camera traps and performed an occupancy analysis that allowed us to obtain an estimate of the initial population and the carrying capacity of the area. We then conducted a population viability analysis whilst simulating seven scenarios that reflect possible con- servation actions. We compared the predictions of these scenarios to determine which conservation actions could in- crease the viability of the population to the greatest extent.


Study area


The area where we studied a local blue-billed curassow population for 5 years (2017–2021) comprises c. 300 km2 within the municipality of Yondó. The area includes parts of the sub-municipalities (veredas) of San Bartolo, Santa Clara, Barbacoas, Bocas de Barbacoas, La Ganadera and Cienaga Chiquita (Fig. 1). Mean annual precipitation is 2,732 mm, with amean annual temperature of 28°C and rel- ative humidity of 76–81%. There are dry periods in June– September and December–March and rainy periods in April–May and October–November (Corantioquia, 2005). The landscape comprises a mosaic of land-cover types,


including pastures, grasslands, secondary vegetation, wet- lands, forests (in various states of preservation), sandy areas, agricultural areas and waterbodies (Fig. 1). As with most humid forests of the Magdalena Valley, this territory has been affected significantly by deforestation, a process that has reduced the forest to patches, most of them small (González-Caro & Vásquez, 2018). This area contains one of the few remaining populations of blue-billed curassow. Once ranging across northern Colombia and the Middle


Magdalena Valley, the species is now limited to a few large remnant forests, including the dry forests in Tayrona National Park, the Serranía de San Lucas massif and the forest patches in the Middle Magdalena Valley.


Methods


We first performed occupancy analysis using camera-trap data we collected in the study area in 2017 (see details below). The results from this analysis allowed us to deter- mine the initial population (N0) and carrying capacity (k) variables. We then used these results to perform a pop- ulation viability analysis.


Occupancy


To assess the presence of the blue-billed curassow in the study area, we used single-season occupancy models, which describe the proportion of the area occupied by a species whilst correcting for detection errors (MacKenzie et al., 2006). We used motion-sensitive infrared flash cameras (Reconyx HC500, Reconyx, Holmen, USA) to detect the blue-billed curassow. We divided the sampling area into a grid of 1 × 1kmcells and selected 29 cells with.10%of forest in which to set the camera traps, covering the heterogeneity of the landscape. We surveyed during the dry season of 2017 using one camera trap per cell for 60 consecutive nights. We considered 19 anthropogenic and environmental


variables (Table 1) that could potentially influence the spe- cies’ occupancy. We included the area of each of the land- cover types at two scales: the 1 × 1 km grid cells, and with a 1-km buffer around each cell (i.e. a cell size of 3 × 3 km). As C. alberti is a terrestrial species associated with forests, uses tree strata from the ground to the canopy (Cuervo et al., 1999; Quevedo et al., 2008) and could be affected differen- tially by forest structure and flooding, for the land-cover variables we considered the overall forest area and the areas of the main forest types: fragmented vs dense; flooded vs upland; tall (canopy .15 m) vs low (canopy 5–15 m). Additionally, we used two anthropogenic variables: min- imum distance to human settlements and minimum dis- tance to roads, which account for accessibility and are assumed to be correlated with the probability of hunting. We adjusted the occupancy models in two steps: first ad-


justing for the probability of detection and then adjusting for the probability of occupancy. For detection we divided the sampling days into different time periods to establish the number of replicates. By identifying the model with the best fit, using the Akaike information criterion, we considered replicates of 5, 10, 15 and 20 clustered days (data not shown) and found that the best fit was obtained when grouping 15 days as a detection event. Additionally, we incorporated two detection variables: the area of forest and the area of pasture within the cell. Although there were no differences


Oryx, 2023, 57(2), 239–247 © The Author(s), 2023. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605322000060


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