Boeken, M.

Premise of research. Small populations on small islands are intrinsically more vulnerable to population decline and extinction. Nevertheless, small native populations that occur on multiple islands may have life history characteristics that buffer impacts from novel disturbance regimes, and rather than populations contracting, they may be expanding. We monitored three populations of the orchid Brassavola cucullata from two Caribbean islands and asked what is the likelihood of population persistence.

Methodology. Over 3-4 years, we recorded growth, fruit production, herbivory, recruitment and mortality for all plants in each of our populations. We assessed persistence and predicted possible population changes using both population projection models (PPM) and integral projection models (IPM). Our results include a mixture of traditional (lambda, elasticities) and more recent indices (transient dynamics and non-linear sensitivities).

Pivotal results. Growth, reproduction and predicted population persistence varied among years and islands. IPM and PPM gave similar results. The overall trend is for a reduction in population growth rates, although population reactivity may buffer this pattern in the short-term (λ > 1). Populations would be extremely vulnerable to reduction if small plants dominated, yet even with an abundance of large plants, substantial reductions in population density are possible. Medium and larger plants contribute more to the persistence of the population, yet survival and growth of small individuals might have greater effect on lambda if retrogression is observed. To attain population stability, effective recruitment rates must increase dramatically.

Conclusions. Populations of perennial plants on small islands can fluctuate substantially suggesting a degree of vulnerability. While B. cucullata shows a general trajectory of decline, there are some signs of stability despite deforestation and herbivore activity. The outlook is precarious for the Saba population given the predominance of younger plants, and all three populations could decline if spasmodic recruitment fails to occur, which may happen if disturbance regimes change and the ongoing warming and drying trends persist.

Keywords: Brassavola cucullata - population dynamics - Lesser Antilles - transient dynamics - island conservation - Orchidaceae 

Abstract The avifauna of the Dutch Caribbean island of Saba has been little studied, as the last comprehensive publication dates from 1983. Here I document 31 new species records up to 2016, including some introduced species, and I discuss new and notable avifaunal developments for the island. 

Keywords avifauna, birds, Caribbean Netherlands, checklist, Dutch Caribbean, Saba

In 2011 and 2012 the breeding success of Red-billed Tropicbirds Phaethon aethereus mesonauta was monitored on Saba, a 13-km2 island in the Caribbean Netherlands. The two colonies on the south and south-west side of the island both contain approximately 100–300 nests; breeding success was zero at these sites, due to predation of newly hatched chicks by Feral House Cats. In the single large colony of Old Booby Hill (estimated to contain approximately 1000 nests) on the east side of the island, rates of predation were lower, resulting in a breeding success (survival from laying until fledging, as far as observed) of 65%. Calculations of daily survival of eggs and chicks following Mayfield, resulted in a nesting success of 48% per pair. I conservatively estimated the size of the Saba breeding population to be at least 1300–1500 pairs, which is larger than the previous estimate of 750–1000 pairs. Potentially, the number of breeding pairs may be as high as 1850 pairs. 

Summary.
 
Based on the literature and own observations a checklist is provided with 27 species of land- and freshwater snails that may occur on Saba, a Dutch island in the Lesser Antilles. Nine species are recorded for the first time from Saba. 

Bijzondere uitgave van ‘Orchideeën’, tweemaandelijks tijdschrift van de Nederlandse Orchideeën Vereniging, met een special over Saba. Michiel Boeken, voor deze gelegenheid gastredacteur, woonde en werkte twee jaar lang op Saba en maakte onder andere een inventarisatie van de orchideeën die er voorkomen. Dat zijn er meer dan twintig, en dat is veel voor een eilandje van amper vier kilometer in doorsnede. Hoe valt die soortenrijkdom te verklaren? En wanneer bloeien de meeste orchideeën? Na een inleiding over Saba volgt een uitgebreid geannoteerde lijst van orchideeensoorten per vegetatiezone waar zij voorkomen, van de kliffen en droge bossen tot het regenwoud en het nevelwoud, plus de op het eiland voorkomende exotische orchideeen en niet waargenomen, maar mogelijk wel op het eiland voorkomende soorten. Alle soorten zijn geillustreerd met fraaie foto's van de auteur.