242 I. F. Valencia et al.


TABLE 1 Variables used to assess the probability of occupancy of the blue-billed curassow Crax alberti in the municipality of Yondó, Colombia (Fig. 1). Cell-scale and buffer-scale indicate the area at which land cover types were measured; Access was used as a proxy for anthropogenic effects and corresponds to Euclidian dis- tances to human settlements and infrastructure.


Type


Cell-scale (1 × 1 km) land cover


Variable


Forest (all classes combined) Dense tall upland forest Dense tall flooded forest Dense low flooded forest Fragmented forest Secondary vegetation Open pasture


Buffer-scale (3 × 3 km) land cover


Forest (all classes combined) Riparian forest Dense high upland forest Dense high flooded forest Dense low flooded forest Fragmented forest Swamp Open pasture Secondary vegetation


Access


Minimum distance to drainage Minimum distance to settlements Minimum distance to roads


being uninhabited at present. The age structure of the popu- lation is also unknown; therefore, we established a stable dis- tribution for all of the simulated scenarios, making the number of births equal to the number of deaths. We ran each simulation with 100 iterations to 100 years and defined as viable populations those with a probability of survival .0.4 at the end of the simulation time.


Initial population size and carrying capacity


Weestimated the initial population size (N0) using Equation (1):


N0 = A(Occu≥0.7)d 1


whereA(Occu$0.7) is the area of non-flooded forest within the study area with an occupancy value of$0.7 and d the popu- lation density. We used two population density values: one low estimate of 1.66 individuals/km2 reported in the muni- cipality of Maceo, Antioquia (González, 2004) and a higher estimate of 2.5 individuals/km2 obtained from the reserve El Paujil, in the departments of Boyacá and Santander (Rodríguez, 2006). We generated two groups of scenarios with these initial density values (Table 3). We calculated the carrying capacity (k) again, using Equation (1), but re- placing A(Occu$0.7) with A(Total), with the latter corresponding to the total non-flooded forest area, thus assuming that the entire forest habitat would be occupied. To include the dir- ect effect of deforestation on habitat loss and thus k,we added an annual change of –0.8% to the carrying capacity


Mortality by age is unknown for the natural populations of C. alberti. To obtain this parameter, we used as a reference the mortality proposed for a population of the red-billed curassow Crax blumenbachii in Brazil (São Bernardo et al., 2014). We assumed the following for both sexes: indi- viduals of 0–1 year, 35% mortality; 1–2 years, 25%; 2–3 years, 10%; and $3 years, 8%. Based on information collected by Houston Zoo (C. Holmes, pers. comm., 2016), we used a maximum age of 25 years for both males and females, with this also being the maximum reproductive age.


Catastrophes


Catastrophes are natural environmental events outside nor- mal variation (e.g. hurricanes, floods, diseases or similar events) and can affect the reproduction and/or survival of a species. The probability of a rapid population decrease in vertebrates has a high correlation with generational time: the probability that a population experiences a catas- trophe causing a reduction of 50% in the population is 14% per generation (Reed et al., 2003). To incorporate this value for C. alberti, we assumed a catastrophe probability of 14% every 7 years (i.e. the generation time of the species) or 2% per year, with each catastrophe causing a 50% reduction in the survival of the population. These catastrophes could occur in real scenarios as a result of climate variations or dis- eases affecting the species, increasing the mortality of young individuals or affecting the nesting success.


Annual mortality from hunting


Wehave received reports of hunting of C. alberti but there is no detailed information regarding the number of indivi- duals hunted per year. We used mortality from hunting of five adults ($3 years; four male and one female) and two juveniles (0–1 years; one male and one female) per year based on informal conversations with local people. The number of adult males is higher as hunters can detect them during the breeding season from the sounds they use to gain the attention of females.


Conservation scenarios


With regards to the various conservation actions that could be implemented and have been discussed in meetings and workshops, we created seven scenarios to evaluate the re- sponse of the population to changes in population size, car- rying capacity and mortality from hunting (Tables 4 & 5).


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


during the first 30 years of the simulation. We estimated this forest loss rate in the landscape based on the per cent of forest cover loss in the territory during 2000–2014, which was 10.9%total or 0.8%per year (Hansen et al., 2013).


Annual mortality and longevity


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