Victória Benemann

Victória Benemann

Universidade do vale do Rio dos Sinos

Victória's lectures

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3rd World Seabird Conference

Potential nesting distribution of Masked Boobies (Sula dactylatra) breeding at the remote Trindade Island, western South Atlantic


Modeling suitable habitats for biodiversity maintenance under changing environments may serve as an important tool for biological conservation purposes. Trindade and Martim Vaz is an oceanic archipelago located ~1.200km from the coast of Brazil, and has been under ecological succession since feral goat eradication, which have devastated its original vegetation. We modeled nesting habitat suitability of a surface-nesting seabird - the Masked Booby Sula dactylatra - at Trindade Is. and predicted its breeding distribution on the island. We mapped 44 active nests of S. dactylatra during the breeding seasons of 2017 and 2019, from October to November at Trindade Is. We fitted nest occurrence points in response to five topographical (Elevation, Slope, Insulation, Aspect and Flow Length) and two vegetation (Succession and Remnant) variables, using an Ensemble Species Distribution Model (ESDM) of four different algorithms: Boosted Regression Trees - GBM, Random Forests - RF, Generalized Linear Models - GLM, and Generalized Additive Model. We evaluated model accuracy based on two metrics: ROC and AUC, and tested for multicollinearity between variables using VIF test. Analyses were performed using the "biomod2" package in software R 3.6.1. Our models showed accuracy above 0.8 in both used metrics (ROC and TSS). Our results indicate areas of very high nesting habitat suitability along the Southwest and Northwest faces of Trindade Is., mostly in elevations varying from 200-400 m (Fig. 1). Elevation and Insulation were the variables that better explained S. dactylatra selection for nesting habitats, while Succession was the one that contributed less (Fig. 2). Since S. dactylatra depends on exposed rocky soils to nest, and that the successional vegetation of Trindade Is., that is already covering most of the Eastern faces, is likely to spread along the Western faces of the island, it is expected to reduce nesting habitat availability for this species in the coming decades.


Victória Benemann¹, Leonardo Dorneles¹, Rosalinda Montone², Maria Petry¹

¹University of Vale do Rio dos Sinos, ²University of São Paulo


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