Dispersie na het broedseizoen, trek en overwintering van Grote Sterns <i>Thalasseus sandvicensis</i> uit de Voordelta = Post-breeding dispersal, migration and wintering of Sandwich Terns <i>Thalasseus sandvicensis</i> from the southwestern part of the Netherlands

The Sandwich Tern Sterna sandvicensis is a Dutch Red List species with a population of 19,000 pairs in the Dutch coastal zone. It winters off the coasts of Africa and a small populations migrates into the Mediterranean or stays even more north.. In the Netherlands, breeding takes places in a small number of colonies in the Delta area and the Waddensea. In this study, Sandwich Terns from the Delta colony on the Scheelhoek (Natura 2000 SPA ‘Haringvliet’) were investigated which forage during the breeding season in Natura 2000 SPA ‘Voordelta’. In total 30 adult Sandwich Terns were equipped with radio transmitters, a colourring and a plumage colour (picrinic acid or silver nitrate solution). Thanks to these markings birds could be followed in the colonies, from airplanes and from the coast. Several birds used the sand banks off the coast of their breeding colonies to rest after the breeding season. After a short while they dispersed in western and northern direction with sightings in the northern part of the Netherlands (outside and within other colonies). These were always failed breeders, possibly scouting other colonies for future breeding places. Some of these birds even left the Dutch coasts and appeared in Scotland and Denmark. Adults with young probably dispersed into the North Sea after a short stay around the sand banks off the coast near the colonies. They probably head to more nutrient rich areas in the North Sea and adjacent areas where the young birds can practice their fishing techniques before they move south. The adults can build-up here good fat reserves before the start of migration. In September, most of the marked Sandwich Terns were south of their breeding places and during their southward migration birds were seen along the coast of France and on Lanzarote (Canary Islands). Our results showed that using markers on birds could yield good data with a resighting percentage of 20% within only one year. Furthermore, the use of plumage colouring proved to be a good method for obtaining information of individual birds as these colourings attract the attention of observers and are ‘readable’ over large distances

Local Birds in and around the Offshore Wind Park Egmond aan Zee (OWEZ) (T-0 & T-1)

The Dutch consortium "NoordzeeWind" operates the first offshore wind farm in Dutch North Sea waters. The park, consisting of 36 turbines on monopiles, is located NW of IJmuiden harbour, some 8 NM off the Dutch mainland coast. Named after the nearest town ashore, the park will be known as "Offshore Wind farm Egmond aan Zee" (OWEZ). A second offshore wind farm has also become operational, the Princess Amalia Windfarm (PAWF). This report deals with distribution patterns of local seabirds in an area of approximately 885 km2 around the OWEZ and PAWF park

Distribution maps of cetacean and seabird populations in the North‐East Atlantic

1. Distribution maps of cetaceans and seabirds at basin and monthly scales are needed for conservation and marine management. These are usually created from standardized and systematic aerial and vessel surveys, with recorded animal den- sities interpolated across study areas. However, distribution maps at basin and monthly scales have previously not been possible because individual surveys have restricted spatial and temporal coverage. 2. This study develops an alternative approach consisting of: (a) collating diverse survey data to maximize spatial and temporal coverage, (b) using detection func- tions to estimate variation in the surface area covered (km2) among these surveys, standardizing measurements of effort and animal densities, and (c) developing species distribution models (SDM) that overcome issues with heterogeneous and uneven coverage. 3. 2.68 million km of survey data in the North-East Atlantic between 1980 and 2018 were collated and standardized. SDM using Generalized Linear Models and General Estimating Equations in a hurdle approach were developed. Distribution maps were then created for 12 cetacean and 12 seabird species at 10 km and monthly resolution. Qualitative and quantitative assessment indicated good model performance. 4. Synthesis and applications. This study provides the largest ever collation and standardization of diverse survey data for cetaceans and seabirds, and the most comprehensive distribution maps of these taxa in the North-East Atlantic. These distribution maps have numerous applications including the identification of im- portant areas needing protection, and the quantification of overlap between vul- nerable species and anthropogenic activities. This study demonstrates how the analysis of existing and diverse survey data can meet conservation and marine management needs.Versión del editor4,7

Dietary variation in chick-feeding and self-provisioning Cape Petrel Daption capense and Snow Petrel Pagodroma nivea at Signy Island, South Orkney Islands, Antarctica

Food web knowledge is a prerequisite for adequate resource management in the Antarctic ecosystem. Accurate dietary specifications for the major consumers within the Antarctic ecosystem are needed. Procellariid species are the most numerous avian species in Antarctica and account for 20% to 40% of the overall consumption by seabirds in the area. Diet composition of two important procellariids, Cape and Snow Petrels, was studied at Signy Island during the breeding season 2005–2006. Food samples were obtained by stomach flushing of both chick-feeding birds and self-provisioning birds. Original prey mass was reconstructed from identifiable remains in the stomach samples. Significantly different diet compositions were found between chick-feeding and self-provisioning Cape Petrels based on reconstructed weight (chick-feeders 39:61:0:0, fish:crustacean:squid:other; self-provisioning birds 28:65:7:1, F:C:S:O). By contrast, no significant differences were found between chick-feeding Snow Petrels (66:34:0:0, F:C:S:O) and self-provisioning birds (68:32:0:0, F:C:S:O). Dominant prey items were Antarctic Krill Euphausia superba and the myctophid fish Electrona antarctica. Compared with findings undertaken at other locations, Cape Petrels at Signy Island had higher dietary fractions of crustaceans. Similarly, this study shows higher fractions of krill and lower fractions of fish in Snow Petrels at Signy Island than at other locations. A reasonable explanation for the high crustacean fraction in both seabird species might be the local high abundance of Antarctic Krill. This emphasises that local differences in diets need to be taken into account in modelling studies. Also, fish is an abundant prey item in both species, showing that, even in a strongly krill-dominated region, fish may remain an important part of the diet of Antarctic petrel species. The differences in diet between chick-feeding and self-provisioning Cape Petrels also show the importance of studying both groups in overall dietary research

Radio telemetry as an additional tool to study feeding behaviour of breeding Sandwich Tern and Common Tern in the shallow coastal zone of the Netherlands

A large-scale seaward extension of the Port of Rotterdam will cause a decline in feeding habitat for the internationally important populations of Sandwich Tern Thalasseus sandvicensis and Common Tern Sterna hirundo breeding in the N2000 SPA ‘Voordelta’, the Netherlands. Several measures have been taken to counteract the potential negative effects on these colonies. The efficiency of these compensation measures is studied in a multidisciplinary research programme on both biotic and abiotic components. Part of this programme is focused on the breeding and feeding ecology of both tern species. This poster shows the results of the first year of this five-year programme. Diet, feeding ecology and feeding behaviour was studied from a hide placed next to an enclosed part of two colonies (Scheelhoek and Slijkplaat) during the chick rearing period of 2009. Amongst others, time absent from the colony and species and length of prey brought to the chicks were recorded. In addition 15 Sandwich and 30 Common Terns were ringed, coloured and tagged with radio-transmitters. Automatic receivers in the colonies registered presence of tagged terns continuously. Combined with aerial tracking and land-based tracking from the coast spatial distribution of terns in their feeding habitat was studied