avian community

The Jan Thiel lagoon can be considered the most important wetland of Curaçao based on its combined value as a feeding habitat for terns. As is likely the case in general with the other saliñas of Curaçao, Jan Thiel lagoon appears to be of the greatest significance to flamingos during the dry season when the larger wetlands in Venezuela run dry. The lagoon is also an area that has historically provided conditions suitable for massive nesting by rare species of terns. Nesting by terns still occurs but on a much lesser scale and with fewer species. During the rainy season, and because of the presence of many dams which retain fresh water on the eastern half of the lagoon, the area is of persistent value to several waterbirds which showed a preference for feeding in less saline water. These include species such as ducks, sandpipers, and black-winged stilts.

The lagoon is approximately 80 ha and is surrounded by approximately 228 ha of additional scenic conservation area which contain rare tracts of native vegetation and which provide valuable habitat to many other native species such as konènchi, sloke, tapa kaminda, and warawara. The best vegetations are found on the eastern side of the lagoon, particularly the southern quadrant of the eastern half of the lagoon. This quadrant has quite rare vegetation, best described as a Haematoxylon-Coccoloba vegetation in which the dreifi shimaron is found to be abundant on volcanic soil. Such vegetation is also known from areas of Oostpunt, Malpais, and Seru Cocori. Other species remarkably abundant in the Haematoxylon-Coccoloba unit include the mata piska and the palu di pushi while the presence of scattered kibrahacha and mangel di sabana likely indicate species which were once much more abundant but which have somehow survived the intensive use of this area in the past. Rare plant species found in the area include the trees lumbra blanku (Croton niveus), kurahout (Peltophorum acutifolum), mata kombles (Schoepfia schreberi), "fuma machu" (Vitex cymosa). For the latter species, less than 20 trees are known to exist in the Dutch Antilles. 

A major limitation to the avifaunal use of the lagoon, particularly the flamingos and tern nesting is the current high level of uncontrolled recreational disturbance. Unintentional recreational disturbance can likely be greatly reduced by a combination of properly informing visitors, by planting vegetation barriers to shelter visitors from the constant sight of the birds and by partially redirecting trails.

The planned Jan Thiel-Amandelweg road is a major threat to the ecological integrity of the conservation area. The road is protected to lie directly in the two most important freshwater areas bordering the lagoon and on top of one of the four locations which support tern breeding. The mere physical presence of the road is in itself a scourge to the vegetation as is cuts through a part of the Haematoxylon-Coccoloba vegetation and lies directly on top of three (fortunately resprouting) very rare Vitex cymosa trees. If this road is ever built it will add a large source of constant disturbance (incl. traffic noise) for much of the eastern half of the lagoon (which is the principal area used by the avifauna), and a major source of littering and contaminants from vehicles. 

The abandoned landfill of Koraal Specht has not been sealed to prevent rainwater percolation and several seeps were seen to emanate from the landfill and flow into the lagoon. The landfill likely forms a serious long-term threat to the lagoon and a study is needed with regards to the potential leaching of contaminants.

We studied the bird communities of five contrasting semi-natural habitats of Lac Bay, Bonaire, South- eastern Caribbean, during the fall of 2011. A total of 420 point counts were conducted in five different habitats and 63 species were detected. Of these, 31 (49%) were migrants, 24 (38%) were residents, 6 (10%) occurred both as residents and migrants and 2 (3%) were migrants that possibly or irregularly breed. Most migratory species were shorebirds and waders (76%). The bird communities of the ve habitats studied showed signi cant differences in species composition and associated community parameters. Mangrove thicket and salt at habitats had roughly a two-fold higher total species richness and a four-fold higher migratory species richness compared to woodland habitats. In woodland habitats, breeding residents dominated, whereas migratory shore and waterbirds dominated in salt at habitat. The Northern Waterthrush, Parkesia noveboracensis, and Barn Swallow, Hirundo rustica, were the numerically most important migratory passerines. The Reddish Egret, Egretta rufescens, a globally Near-Threatened species, ranked among the top 10 most abundant species of the Lac Bay salt at habitat. Our results suggest that the relatively expansive hypersaline wetlands of Bonaire (of which Lac is only a small part) may be of special signi cance to migratory shore and waterbirds. In contrast to other areas of the Caribbean, invasive exotic birds so far play a minor role in the communities studied.