Koen Devos

Towards the European eradication of the North American ruddy duck

AbstractThe North American ruddy duck is an invasive alien species in Europe, which threatens the native white-headed duck through hybridisation. A substantial population established in the UK following escapes and releases beginning in the 1950s. The species then spread widely within Europe, with records across much of the continent, and viable populations established in Belgium, the Netherlands, France and Spain. An international plan to eradicate the species from Europe has been adopted, but the approaches and intensity of control have varied widely between countries. We report on progress towards eradication across the continent. Numbers in 2013 were less than 7xa0% of the 2000 population, although coordinated action is still required to achieve eradication. The European Union is considering a new legislative instrument on Invasive Alien Species, which is likely to place responsibilities on member states to control named species. Coordinated control across those member states with remaining ruddy duck populations is likely to be an early test of any new responsibilities, with the potential to achieve the first continental scale eradication of an invasive alien species.n

Sediment-benthos relationships as a tool to assist in conservation practices in a coastal lagoon subjected to sediment change

This study explores the relation between sediment composition and intertidal macrobenthos populations in the Zwin nature reserve (Belgium and The Netherlands), a tidal lagoon that is included in the Ramsar list of wetlands of international importance and has been designated as Natura 2000 area, among others due to its function as wintering habitat for shorebirds that feed upon macrobenthic invertebrates. Species response models show highest biomass of these prey species in organically enriched cohesive sediments and a distinct decline in probability of occurrence for most species in coarse sediments. Further, the biomass of macrobenthos declined between 2003 and 2010 in the extensive low intertidal inlet channel concurrent with the coarsening of the sediment over time in this hydrodynamically stressed habitat. In contrast, macrobenthos biomass increased in a sheltered shallow intertidal habitat that acted as a catchment area for finer sediments, therefore facilitating the succession towards a higher elevated habitat with salt marsh vegetation establishment. Hence, spatio-temporal sediment dynamics decreased site quality for intertidal predators due to a reduction in feeding areas over time, and a change in physical sediment properties that alter the macrobenthos species occurrence and population biomass. This study thus illustrates that sediment transport dynamics may affect the functioning of coastal shallow soft-sediment habitats, like coastal lagoons. The presented macrobenthos species response models provide a tool to assist in management actions that enable the conservation of cohesive low intertidal habitats that provide a high food supply to shorebirds, fish and macrocrustaceans.

Reply to the comment on 'Working with population totals in the presence of missing data comparing imputation methods in terms of bias and precision' by Bogaart et al.

Bogaart et al. (2017) indicate in their comment that Onkelinx et al. (2017b) misinterpreted some aspects of the Underhill index (UIndex), Species Trends Analysis Tool for birds (birdSTATs) and TRends and Indices for Monitoring data (TRIM), and, as a consequence, do not sufficiently acknowledge the quality of those methods. We agree that some operational choices and underlying assumptions were not fully clear to us. However, if the documentation was incomplete and/or if variants existed, we made choices and filled in gaps, always in favour of Underhill and TRIM, to test our approach as thoroughly as possible and to guarantee a balanced comparison. In fact, in our paper we acknowledge that under certain circumstances, Underhill and TRIM can work properly (see the results and discussion of our paper), but our main point is that multiple imputation covers a broader range of situations and assumptions, and hence it is more flexible and robust. In practice, we cannot always be sure that the assumptions of Underhill or TRIM are valid. In these circumstances, a method that proves to be more robust is preferable. For instance, Bogaart et al. (2017) mention in their fifth point that it is still an open question within the eco-statistical community whether a negative binomial or a quasi-Poisson distribution is more appropriate. However, with multiple imputation, you can make your own choice according to the context or theoretical insight. With an analytical approach, for a new model, the source code needs to be adapted. In addition, in our paper, we caution that an appropriate model must be carefully selected, and we demonstrate what happens with a less appropriate model. In the following, we reply in greater depth to the statements in Bogaart et al. (2017). Each number corresponds to their numbering.