Conservation of the blue‐billed curassow 245
TABLE 4 The seven scenarios evaluated for the conservation of the blue-billed curassow. Scenario
Description
No_Intervention No conservation action is implemented Hunting_50
Hunting_0 k_Constant
k_Increasing
Environmental education, control & surveillance, & conservation agreements can decrease hunting, so mortality from hunting is decreased by 50% for the whole area of study Hunting is eliminated (i.e. zero individuals extracted per year)
Changes in available habitat directly affect carrying capacity, so available habitat is held constant, mainly by reducing deforestation so that it balances restoration
Protection of forests & reforestation programmes could increase available habitat, so carrying capacity has an annual increase of 0.4% during the first 30 years, which is in agreement with a feasible rate of restoration
Supplementation The population is supplemented eight times, with five captive-bred adult males&five females every 2 years, starting in year 1 & ending in year 17 (the total number of birds supplemented would be 80 over 16 years, based on the present success in captive breeding programmes at Houston Zoo; C. Holmes, pers. comm. 2016)
Protected_Area Conservation agreements or the establishment of reserves can lead to the protection of some patches of forest & the elimination of hunting within their boundaries (conservation agreements have proven effective in increasing occu- pancy of the blue-billed curassow; Forero-Medina et al., 2021). We evaluated the effect of the protection of three properties that contain the largest forest patches in the region: San Bartolo, La Ganadera and Rancho Verde. For this, we modified the initial population viability analysis model by dividing the total population into three subpopulations (Table 5): two subpopulations that include the areas that contain the largest patches of forest & are either being es- tablished as private reserves or have a conservation agreement established with the owners (subpopulations 1 and 3), to which we assigned a hunting value of 0 individuals per year & a constant carrying capacity; & another subpopulation (subpopulation 2) that includes the remaining area outside these properties. Subpopulation 1 corresponds to the San Bartolo ranch & subpopulation 3 is La Ganadera and Rancho Verde ranches combined (Fig. 1). The goal with this approach was to parameterize the protected areas in the landscape (& to assign them no hunting, & maintenance of forest patches) by relying on a spatially structured population model.
TABLE 5 Initial population (N0) and carrying capacity (k) values for the Protected_Area scenarios at low and high initial densities. These values were calculated using N0 =A(Occu$0.7)d and k =A(Total)d for the corresponding areas of each sub-population (Fig. 1). See text for details.
Low density Population 1 (San Bartolo ranch)
2 (Unprotected other areas within the study area)
3 (La Ganadera & Rancho Verde ranches combined)
Total
High density
N0 kN0 k
31 34 46 51 11 55 17 83
16 34 24 51 58 123 87 185
conservation strategies for the long-term persistence of the species. Even with limited information, the comparison of the scenario outcomes provides evidence regarding which of these scenarios will most likely prove successful in the long term. We conclude that without any intervention the popula-
tion is not viable over a 100-year period, with a probability of survival close to zero for the two densities modelled. This is the first analysis of this type for C. alberti, although there are similar studies using population viability analysis for other cracids (Martínez-Morales et al., 2009; São Bernardo et al., 2014). We conclude that the threats to this species are
TABLE 6 Extinction probabilities and mean extinction times (Fig. 3) for all scenarios considered in the population viability analysis of the blue-billed curassow in Yondó.
Scenario
Low density (1.66/km2) No_Intervention Hunting_50 Hunting_0 k_Constant k_Increasing
Supplementation Protected_Area
High density (2.50/km2) No_Intervention Hunting_50 Hunting_0 k_Constant k_Increasing
Supplementation Protected_Area
Extinction probability
1.00 0.89 0.00 1.00 1.00 1.00 0.73
1.00 0.40 0.00 0.86 0.83 1.00 0.31
Mean extinction time (years)
15.7 48.2
.100.0 15.4 16.6 26.9 58.6
35.5 62.2
.100.0 46.8 42.3 42.5 72.5
driving this population to extinction and that implementing further conservation actions is necessary to avoid this. The model confirms the susceptibility of the species to hunting pressure. This agrees with results showing that hunting is the major driver of non-viability of C. alberti populations (Cuervo et al., 1999). The conservation strategies that offer
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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