Bertuol, P.

Abundance estimates based on adequate survey design and count methodology are needed for population monitoring and modelling, and for assessing the results of conservation actions taken to boost or maintain population size at desired target levels. We monitored Bonaire’s population of yellow-shouldered parrot Amazona barbadensis rothschildi using systematic distance sampling surveys in 2009–2017, and developed a Bayesian state-space logistic model to predict changes in abun- dance resulting from increased human-induced mortality in 2018–2066. Survey-based abundance estimates (mean ±bootstrapped SE) were 0.172 ± 0.020 parrots ha–1 and 2924 ± 340 parrots at a survey region covering 17 000 ha. Model- based posterior distribution estimates (mean ± MCMC SD) of maximum population growth rate, maximum sustainable mortality rate, maximum sustainable mortality, population carrying capacity and equilibrium population size were 0.179 ±0.129, 0.090 ± 0.064, 219 ± 135, 5623 ± 2043 and 2811 ± 1022 parrots. With low to moderate mortality rates (0.001– 0.100, 0.101–0.250), predicted population sizes (mean ± MCMC SD) were 2963 ± 668 and 2703 ± 1660 parrots in 2018, and 2754 ± 690 and 2297 ± 1301 parrots in 2066. With high mortality rates (0.251–0.500), predicted population sizes were 1780 ± 1160 parrots in 2018 and 26 ± 139 parrots in 2066. Because the relative importance and magnitude of human–parrot conflicts are unknown but may be unsustainable, we consider the parrot population vulnerable to the risk of extinction during the modelled time horizon. Therefore, we recommend long-term monitoring and modelling for assessing changes in abundance and the results of conservation actions taken to keep the population above 2800 parrots in the survey region (i.e. population size N > 2.5% percentile of the posterior distribution of population carrying capacity K).

Event: BirdsCaribbean 21st International Conference, Topes de Collantes, Cuba, 13-17 July, 2017

Abstract in scientific journal or proceedings

Five species of terns are reported breeding in Bonaire from April to August. For three years, the species Sternula antillarum, Sterna hirundo, Thalasseus maximus, Thalasseus eurygnatha and in 2017 Sterna dougalli were monitored in southern Bonaire during the breeding season, with the objective of suggesting management actions and increasing reproductive success. Monitoring results showed that the main threat is the presence of feral cats. The hatching success for Thallasseus species and Sterna species was relatively similar over the years. However, there are indications that hatching success for Sternula antillarum colonies on roads has increased from 17% (2014) to 36% (2016) after a pilot program for management of invasive predators began in 2015. On the other hand, native predators on artificial islands have had negative effects, suggesting that the creation of spaced islands is important to avoid large concentrations in small areas that favor predation.

Report on the assessement of the population density goats on Bonaire

Raw data of tern observations by STINAPA. The observations include species, habitat and eggs and hatching information,

Please contact STINAPA for more information.

Of the 3 species comprising the genus Leptonycteris Miller, L. curasoae has been the least studied with respect to its long-distance flights and potential for seasonal migrations. We studied long-distance movements between islands and between islands and the mainland in the Curaçaoan long-nosed bat. We used mark–recapture with periodic sampling and marking of bats in Aruba, Curaçao, Bonaire, and 1 location (Butare) in Falcón State, on the Venezuelan coastline. Between October 2008 and April 2014, we captured a total of 7,518 individuals at 11 sites (Aruba: n = 1,827, Curaçao: 778, Bonaire: 4,128, and Butare: 785). Between 78.3% and 98.0% of the bats captured at each island and mainland were marked, and the overall percentage of recaptured animals across all sampling sites was 8.31% (n = 529). L. curasoae inhabits the 3 islands year-round. On each island, it roosts in several caves, which can be used alternatively by the same individuals. Despite being a resident species, L. curasoae can perform long-distance oversea flights between islands and between islands and the South American mainland. A total of 11 long-distance flights were recorded (2 Bonaire–Aruba, 4 Bonaire–Curaçao, 1 Curaçao–Bonaire, 1 Bonaire– Venezuela, and 3 Aruba–Venezuela). We propose that populations of this species in Aruba, Curaçao, Bonaire, and Falcón State, Venezuela, exchange individuals, and part of the insular populations migrate seasonally southward as a response to cyclical changes in local resource availability and the yearly reproductive regime. 

Abstract:

Lionfish (Pterois volitans and P. miles) have spread rapidly throughout the Caribbean Sea since 1985, where they negatively impact native fish communities and therefore are considered by some as the most damaging invasive species in the Caribbean to date. To combat further population growth and spread of lionfish and to protect native fish communities, various Caribbean islands have started control efforts. On Bonaire, a removal program based on volunteers using spear guns was started immediately after the first lionfish was sighted in 2009, and a similar program was started on neighboring Curaçao 2 yr later. To determine the effectiveness of these removal efforts, differences in the density and biomass of lionfish were compared between areas in which lionfish were directly targeted during removal efforts (i.e. ‘fished’ areas) on Bonaire and areas where they were not (i.e. ‘unfished areas’) on both Bonaire and Curaçao. Lion- fish biomass in fished locations on Bonaire was 2.76-fold lower than in unfished areas on the same island and 4.14-fold lower than on unfished Curaçao. While removal efforts are effective at reducing the local number of lionfish, recruitment from unfished locations, such as those too deep for recreational diving and at dive sites that are difficult to access, will continuously offset the effects of removal efforts. Nevertheless, our results show that the immediate start and subsequent contin- uation of local removal efforts using volunteers is successful at significantly reducing the local density and biomass of invasive lionfish on small Caribbean islands.