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Vanaf het Vogeljaar 64(2) publiceren wij de serie ‘De Nederlandse Vogelfamilies’, door Marcel Boer. In deze reeks worden telkens de meest opmerkelijke kenmerken en overeenkomsten van één of meer Nederlandse vogelfamilies beschreven. De artikelen in deze reeks zijn een bewerkte versie van afleveringen die eerder verschenen in het Zaanse vogeltijdschrift ‘de Kieft’. Alle illustraties bij dit artikel zijn getekend door Jos Zwarts.

How food webs are structured has major implications for their stability and dynamics. While poorly studied to date, arctic food webs are commonly assumed to be simple in structure, with few links per species. If this is the case, then different parts of the web may be weakly connected to each other, with populations and species united by only a low number of links. We provide the first highly resolved description of trophic link structure for a large part of a high-arctic food web. For this purpose, we apply a combination of recent techniques to describing the links between three predator guilds (insectivorous birds, spiders, and lepidopteran parasitoids) and their two dominant prey orders (Diptera and Lepidoptera). The resultant web shows a dense link structure and no compartmentalization or modularity across the three predator guilds. Thus, both individual predators and predator guilds tap heavily into the prey community of each other, offering versatile scope for indirect interactions across different parts of the web. The current description of a first but single arctic web may serve as a benchmark toward which to gauge future webs resolved by similar techniques. Targeting an unusual breadth of predator guilds, and relying on techniques with a high resolution, it suggests that species in this web are closely connected. Thus, our findings call for similar explorations of link structure across multiple guilds in both arctic and other webs. From an applied perspective, our description of an arctic web suggests new avenues for understanding how arctic food webs are built and function and of how they respond to current climate change. It suggests that to comprehend the community-level consequences of rapid arctic warming, we should turn from analyses of populations, population pairs, and isolated predator-prey interactions to considering the full set of interacting species.

How food webs are structured has major implications for their stability and dynamics. While poorly studied to date, arctic food webs are commonly assumed to be simple in structure, with few links per species. If this is the case, then different parts of the web may be weakly connected to each other, with populations and species united by only a low number of links. We provide the first highly resolved description of trophic link structure for a large part of a high-arctic food web. For this purpose, we apply a combination of recent techniques to describing the links between three predator guilds (insectivorous birds, spiders, and lepidopteran parasitoids) and their two dominant prey orders (Diptera and Lepidoptera). The resultant web shows a dense link structure and no compartmentalization or modularity across the three predator guilds. Thus, both individual predators and predator guilds tap heavily into the prey community of each other, offering versatile scope for indirect interactions across different parts of the web. The current description of a first but single arctic web may serve as a benchmark toward which to gauge future webs resolved by similar techniques. Targeting an unusual breadth of predator guilds, and relying on techniques with a high resolution, it suggests that species in this web are closely connected. Thus, our findings call for similar explorations of link structure across multiple guilds in both arctic and other webs. From an applied perspective, our description of an arctic web suggests new avenues for understanding how arctic food webs are built and function and of how they respond to current climate change. It suggests that to comprehend the community-level consequences of rapid arctic warming, we should turn from analyses of populations, population pairs, and isolated predator-prey interactions to considering the full set of interacting species.

Stopover ecology is the scientific study of the behaviour of migrants, the interrelationships among migrants, and between migrants and their environment, at stopping sites. Many shorebird species are long-distance migrants and require high quality stopping sites to rest and refuel during migration. The suitability of a stopping site depends mostly on food availability, level of competition, and predation or disturbance pressure. Events at stopover may not only affect migration performance, but also the subsequent reproduction or survival, and therefore become the limiting factor for the population sizes of migrants. The stopping sites in the Yellow Sea along the East Asian-Australasian Flyway are used extensively by long-distance migratory shorebirds along the flyway, but very little is known about the stopover ecology of these birds. Moreover, the stopping sites within the Yellow Sea region are under serious threats; some of them are being lost before their importance to shorebirds is fully understood. In this thesis, my aim was to study the stopover ecology of Bar-tailed Godwits Limosa lapponica and Great Knots Calidris tenuirostris at an important stopping site in the northern Yellow Sea, the Yalu Jiang coastal wetland, during northward migration between 2010 and 2012. I estimated the number of these shorebirds transiting and their passage dates using repeated counts incorporated with Thompson’s modelling approach. I described the type, abundance and characteristics of their benthos resources by benthos sampling. I investigated their dietary compositions, foraging patterns and mechanisms of coexistence by behaviour scans, focal bird observations and faecal dropping analysis. Finally, I studied their predation impact on their main bivalve prey, Potamocorbula laevis, using exclosures. My results indicated that at least 42% of the East Asian-Australasian Flyway’s northward migrating L. l. baueri godwits, 19% of L. l. menzbieri godwits, and 22% of the Great Knots use

Drieteenstrandlopers behoren tot Nederlands meest typische en algemene strandvogels. Uit tellingen blijkt dat ze bovendien steeds algemener worden. Toch is er weinig over deze witgrijze dribbelaars bekend. Zo weten we niet totwelke broedpopulatie(s) de Nederlandse overwinteraars en doortrekkers behoren. Ook is het algemene beeld dat Drieteenstrandlopers, zoals hun naam doet vermoeden, vooral onze stranden bevolken aan verandering onderhevig. Wadplaten zijn in toenemende mate favoriet, zo blijkt uit deze bijdrage over verspreiding en aantallen

This report describes the derivation of parameter estimates for the model DYNAMIG for an arctic breeding shorebird, the Knot. DYNAMIG predicts the optimal spring migration of birds, like shorebirds and geese, that depend of a chain of discrete sites, to travel between their breeding grounds and their wintering grounds. An important parameter is the terminal reward, which describes the fitness consequences of arriving with a particular body condition at a particular time on the breeding grounds. We derived the terminal reward from field studies in Siberia carried out as part of this project. Other parameter values, like flight costs, maintenance metabolism and predation risk were derived from the literature. Predictions on aspects of the migration schedule with the parameterized model were partly correct and partly wrong. Suggestions are made how to remedy the discrepancies. An interesting prediction of the model that requires testing is that Knots breeding in Canada migrate via Iceland, whereas Knots breeding on Greenland migrate via Norway. A sensitivity analysis indicated that this prediction was quite robust.

Om de rol van de Waddenzee en de achtergronden van de wadvogeltrek beter te begrijpen doen Nederlandse vogelonderzoekers in het kader van de WIWO (Stichting Werkgroep Internationaal Wad- en Watervogelonderzoek) al vele jaren onderzoek aan wadvogels en waddengebieden elders in de wereld. In eerste instantie werden vergelijkingen gemaakt tussen hele wadvogelgemeenschappen en tussen de hoeveelheden bodemdieren beschikbaar als wadvogelvoedsel; later kwamen ook soortspecifieke ecologische eigenschappen als opvetsnelheid en energieverbruik in beeld. In dit artikel een voortgangsreportage van dit type onderzoek met o.a. een vergelijking van de voor- en nadelen van overwinteren in een West-Afrikaans waddengebied t.o.v. de Waddenzee of andere gebieden in Noordwest-Europa, en de ecologische aspecten van de trek van diverse populaties van de kanoetstrandloper Calidris canutus (gekozen als modelsoort voor wadvogels die aan lange-afstandstrek doen)

In 1999 ontdekte men dat de klierenproductie van kanoeten uit di-esters bestond, in plaats van de alom bekende mono-esters. Een nader onderzoek vanuit NIOZ en Dierecologie (Groningen) naar de seizoensgebondenheid en de mogelijke oorzaken (betere bescherming van het verendek of betere camouflage)

Door middel van zendertjes en automatische ontvangststations in de westelijke Waddenzee werden de bewegingspatronen tussen de foerageerbebieden en de hoogwaterverblijfplaatsen van de kanoet-populatie in beeld gebracht, en konden verbanden worden gelegd met het voedselaanbod op verschillende locaties. Verslag van lopend onderzoek