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Making inferences about non-detection observations to improve occurrence predictions in Venezuelan Psittacidae

Published online by Cambridge University Press:  22 January 2020

JOSÉ R. FERRER-PARIS
Affiliation:
Centro de Estudios Botánicos y Agroforestales. Instituto Venezolano de Investigaciones Científicas (IVIC). Apartado 20632, Caracas 1020-A Venezuela. Current affiliation: University of New South Wales, School of Biological, Earth and Environmental Sciences, NSW, Kensington 2052, Australia.
ADA SÁNCHEZ-MERCADO*
Affiliation:
Ciencias Ambientales, Universidad Espíritu Santo, Ecuador. Provita, Chacao, Caracas 1060, Venezuela.
*
*Author for correspondence; email: ay.sanchez.mercado@gmail.com
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Summary

The global decline in psittacid populations highlights the need for monitoring programmes that allow us to estimate the level of confidence that can be placed in a non-detection observation in order to assess changes in range status. We used the detection/non-detection records for 26 psittacid species detected during the first national bird monitoring programme in Venezuela carried out in 2010 by the Neotropical Biodiversity Mapping Initiative. We fitted occupancy models and evaluate the suitability of the data to explain the lack of detections given the current sampling effort, and the expected occurrence probabilities due to environmental conditions (conditional probability of occurrence; ΨCONDL). We were able to fit reliable models for 13 of the 26 species detected. For Green-rumped Parrotlet Forpus passerinus, Blue-headed Parrot Pionus menstrus, and Orange-winged Amazon Amazona amazonica, the probability of detection (p) under the current sampling effort was too low (> 0.2) in areas where environmental conditions would imply high ΨCONDL (< 0.3). This suggests that sampling effort should be increased to generate reliable estimations of occurrence. In contrast, for Scarlet Macaw Ara macao, Yellow-crowned Amazon Amazona ochrocephala, Orange-chinned Parakeet Brotogeris jugularis and Brown-throated Parakeet Eupsittula pertinax the model estimated high p (< 0.3) and low ΨCONDL (> 0.2), suggesting that the species are reliably detected and better models could be obtained by including other predictive variables related to temporal use of resources and habitat heterogeneity. To improve the effectiveness of parrot monitoring programme in Neotropical countries, we suggest increasing the sampling effort, developing several surveys per year, and including variables related with temporal use of resources and habitat heterogeneity.

Information

Type
Research Article
Copyright
© BirdLife International, 2020
Figure 0

Table 1. Psittacidae species reported for Venezuela. Distribution description, conservation categories, and population trend for each species according IUCN is shown. The number of NeoMaps sampling sites overlapping with the expected distribution of the species according to the available range maps from BirdLife is shown. The number of sites with detections, the ratio of current/expected detections and the number of detections for each Venezuelan psittacid species reported in Global Biodiversity Facility (GBIF) in 2010 is shown. The total number of sites sampled was 1,350.

Figure 1

Figure 1. Sampling universe consisted in 170 half-degree cells defined in the Venezuelan Biodiversity Grid. Numbers indicate NeoMaps’ cells code visited by survey teams in 2010.

Figure 2

Table 2. Top performing occupancy models for 13 psittacid species with at least one detection during NeoMaps surveys. The sampling size used to fit each model is shown as the total number of sites within species range sampled during NeoMaps surveys, as well as the number of sites where each species was detected is indicated (detections). AICc = corrected Akaike Information Criterion. ΔAICc = the difference between the AIC for the ith model and the lowest AIC among all the models. AICw = relative weight from the differences in values of AICc. LL = 2log likelihood. The model with the best performance by species is in bold.

Figure 3

Figure 2. Spatial prediction of the (unconditional) probability of occurrence for the whole country based on the model with highest support for each species (Table 2) and the values of the vegetation and climatic covariates. Darker colours indicate higher probabilities. a) Amazona amazonica; b) Amazona farinosa, c) Amazona ochrocephala; d) Brotogeris jugularis; e) Eupsittula pertinax; f) Forpus passerinus; g) Pionus menstruus.

Figure 4

Figure 3. Model predictions. a) Detection probability (p*) = Sampling effort required to detect the species at least once conditional on its presence. b) Conditional probability of presence given that the species was not detected (ΨCONDL).

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Ferrer-Paris and Sánchez-Mercado supplementary material

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