Sjoerd Duijns MSc
PhD Student Marine Ecology		Diet choice Time budgets Interference competition Foraging ecology
sjoerd.duijns@nioz.nl
Visiting address:	Postal address:	CV Research Interests Projects Downloads
Landsdiep 4 NL-1797 SZ 't Horntje (Texel) The Netherlands   Tel. (+31) (0)222-369355 Fax: (+31) (0)222-319674	P.O. Box 59, NL-1790 AB Den Burg The Netherlands

 

CV	Top ^
Personal
Family name         First name(s) Date of birth Place of birth	Duijns Sjoerd 6 October 1976 Breda, The Netherlands
Education
2008                     2004 1999	MSc Ecology, University of Wageningen   Major thesis: Spring migration of two Bar-tailed Godwit (Limosa lapponica) populations in the Dutch Wadden Sea (NIOZ) Minor thesis: Interference competition among Mallards (Anas platyrhynchos) (NIOO-KNAW) 2nd Minor thesis: Body condition of Barn Swallows (Hirundo rustica) in relation to different roost sizes in Zambia (Birdlife Netherlands)   BSc Wildlife Management, van Hall institute, Leeuwarden Intermediate Professional Education Land-, Water- and Environmental studies, MBCS Velp.
Employment record
2009 – 2013 2009	PhD student at NIOZ Lab technician at NIOZ

 

Research Interests	Top ^
During the last decade the composition within the Wadden Sea’s waterbirds has drastically changed. Bivalve predators as Red Knot, Calidris canutus, Oystercatcher, Haematopus ostralegus and Common Eider, Somateria mollissima have severely declined in numbers, whereas polychaete predators have increased (e.g. Bar-tailed Godwit Limosa lapponica, Dunlin Calidris alpina and Grey Plover Pluvialis squatarola. Clearly, this suggests that the observed changes in number of birds present are linked to changes in the benthic fauna. Fortunately due to long term monitoring of the numbers of shorebirds and their benthic prey more understanding is gained how these numbers are influenced. Indeed, very recently, the dramatic decline of Red Knots from the Wadden Sea could be attributed to the decline in food abundance, which had been derived from the NIOZ 15-yr-long benthic survey throughout the western Dutch Wadden Sea. With this long term survey, it became apparent that shellfish stocks largely collapsed due to dredging, while polychaete stocks remained at a constant level or even increased. The changes in food stocks are likely to be responsible for the changes in species abundance that rely on the intertidal Wadden Sea area. The question remains, whether the increase of worm-eating birds are in fact driven by a possible increase of food abundance.                   Shorebirds forage on benthic prey during low tide on intertidal mudflats which differ in the degree of food availability, food quality and predation risk. To decide where to forage, migratory shorebirds trade off the costs and benefits of different habitats to maximize their survival. To measure the available densities of the benthic prey the NIOZ started a long-term benthic research effort that began in 1988. In 2008 this effort has expanded and the entire Dutch Wadden Sea area is being sampled in a fixed 500m grid and all polychaete species are included (previously the larger polychaetes were only counted) and analyzed in the lab. This enables us to create a food landscape of the entire Wadden Sea per benthic species. Historically our research group has gained much understanding of the foraging ecology of the Red Knot (Calidris canutus) and in 2001 a new study species has been included in our work, the Bar-tailed Godwit (Limosa lapponica). This species is predominantly a polychaete feeder and thus provides us with a mirror species to the already well known Red Knot.

 

Projects	Top ^
Foraging ecology of a long distant migrant, the Bar-tailed Godwit, Limosa lapponica

 

Link	Top ^
·         Color ring program of Bar-tailed Godwits

 

Downloads	Top ^
Internship or thesis positions for MSc and BSc students are available throughout the year. There are also opportunities for shorter periods to gain experience in the field, laboratory or with data analyses. If you are interested in an internship or thesis please don’t hesitate to contact me and we can discuss the possibilities for a suitable project.

 

Selected Publications	Top ^
Duijns S., Jukema J., van Horssen P., Spaans B., & Piersma T. (revision submitted). Revisiting the proposed leap-frog migration system of Bar-tailed Godwits along the East Atlantic Flyway. Ardea.   Van Dijk J.G.B., Duijns S., Gyimesi A., de Boer W.F. & Nolet. B.A. Birds Foraging on a Heterogeneous Food Distribution with Two Competitors Achieve the Same Intake Rate as when Foraging Alone. Ethology (online)   Duijns, S., van Dijk, J. G. B., Kraus, R. H. S., Mateman, A. C., van den Brink, B. and van Hooft, P. 2011. An additional field method to sex adult Barn Swallows during the non-breeding season in Zambia: white spot length in the outer tail feather. Ostrich 82: 129-134. (pdf)   Duijns S., van Dijk J.G.B., Spaans B., Jukema J., de Boer W.F., Piersma T. 2009. Foraging site selection of two subspecies of Bar-tailed Godwit Limosa lapponica; time minimizers accept greater predation danger than energy minimizers. Ardea 97 (1): 51-59. (abstract)   Van Dijk J.G.B., Duijns S., Mos J. and Urbina Ruiz M. 2008. Multiformity at risk in Dutch newspapers? A case study on the ‘Probo Koala’, an environmental incident. CCP 2:67-81
National journals: Duijns S, Dusseljee S. 2005. Hebben de Muskusrattenbestrijdende instanties in Nederland voldoende kennis om de muskusrat (Ondatra zibethicus L.) succesvol te bestrijden? Muskusrat en Beheer.