Royal Netherlands Institute for Sea Research
Royal Netherlands
Institute for Sea Research
Phone number
+31 (0)222 369 418

Dr. Tamar Lok



  • Population ecology, mark-recapture analysis
  • Evolution, phenotypic plasticity, developmental plasticity
  • Migration
  • Environmental change
  • Foraging ecology, habitat choice

Research interests

I am a biologist with a broad interest in animal behaviour, population ecology and evolution. I have a special interest in the evolution of migratory behaviour. Understanding the mechanisms underlying the intriguing phenotypic variation in migratory behaviour will learn us more about the flexibility and constraints of migratory animals to keep track in a world that is constantly changing. 



2017-present: Post-doctoral researcher, NIOZ Royal Netherlands Institute for Sea Research, Texel, The Netherlands. Project: Individual development of migratory strategies of coastal birds.

2015-2016 : Post-doctoral fellow (Rubicon fellowship), Centre d’Ecologie Fonctionelle et Evolutive, CNRS, Montpellier, France.  Project: The adaptability of migratory animals to a rapidly changing world: novel measures from an integrated analysis of count, mark-recapture and telemetry data. Collaborators: Dr. Olivier Gimenez, Dr. Roger Pradel

2013–2014: Post-doctoral researcher, Animal Ecology Group, University of Groningen, The Netherlands. Project: Demography of waders along the East-Asian Australasian flyway. Collaborator: Prof. Theunis Piersma



Jouta, J., de Goeij, P., Lok, T., Velilla, E., Camphuysen, C.J., Leopold, M., van der Veer, H.W., Olff, H., Overdijk, O. & Piersma, T. (2018). Unexpected diet preferences of Eurasian Spoonbills in the Dutch Wadden Sea: Spoonbills mainly feed on small fish instead of shrimp. Journal of Ornithology 159:  839-849.

Oudman, T., de Goeij, P., Piersma, T. & Lok, T. (2017). Colony-breeding Eurasian Spoonbills in The Netherlands: local limits to population growth with expansion into new areas. Ardea 105: 113-124.

Lok, T., Veldhoen, L., Overdijk, O., Tinbergen, J.M. & Piersma, T. (2017). An age-dependent fitness cost of migration? Old trans-Saharan migrating spoonbills breed later than those staying in Europe, and late breeders have lower recruitment. Journal of Animal Ecology 86: 998-1009.

van den Hout, P., Piersma, T., ten Horn, J., Spaans, B. & Lok, T. (2017). Individual shifts toward safety explain age-related foraging distribution in a gregarious shorebird. Behavioral Ecology 28: 419-428.

Van Gils, J.A., Lisovski, S., Lok, T., Meissner, W., Ozarowska, A., de Fouw, J., Rakhimberdiev, E., Soloviev, M.Y., Piersma, T. & Klaassen, M. (2016) Body shrinkage due to Arctic warming reduces red knot fitness in tropical wintering range. Science 352: 819-821.
Conklin, J.R., Lok, T., Melville, D.S., Riegen, A.C., Schuckard, R., Piersma, T. & Battley, P.F. (2016) Declining adult survival of New Zealand Bar-tailed Godwits during 2005–2012 despite apparent population stability. Emu 116: 147-157.
Piersma, T., Lok, T., Chen, Y., Hassell, C.J., Yang, H.-Y., Boyle, A., Slaymaker, M., Chan, Y.-C., Melville, D.S., Zhang, Z.-W. & Ma, Z. (2016) Simultaneous declines in summer survival of three shorebird species signals a flyway at risk. Journal of Applied Ecology 53: 479-490.
Lok, T., Overdijk, O. & Piersma, T. (2015) The cost of migration: spoonbills suffer higher mortality during trans-Saharan spring migrations only. Biology Letters 11: 20140944. 
Lok, T., Overdijk, O. & Piersma, T. (2014) Interpreting variation in growth of Eurasian Spoonbill chicks: disentangling the effects of age, sex and environment. Ardea 102: 181-194. 
El-Hacen, E.M., Piersma, T., Jouta, J., Overdijk, O. & Lok, T. (2014) Seasonal variation in the diet of Spoonbill chicks in the Wadden Sea: a stable isotopes approach. Journal of Ornithology 155: 611-619. 
Lok, T., Overdijk, O., Tinbergen, J.M. & Piersma, T. (2013) Seasonal variation in density dependence in age-specific survival of a long-distance migrant. Ecology 94: 2358-2369. 
El-Hacen, E.M., Overdijk, O., Lok, T., Olff, H. & Piersma, T. (2013) Home range, habitat selection, and foraging rhythm in Mauritanian spoonbills (Platalea leucorodia balsaci): a satellite tracking study. Waterbirds 36: 277-286. 
van Gils, J.A., van der Geest, M., Leyrer, J., Oudman, T., Lok, T., Onrust, J., de Fouw, J., van der Heide, T., van den Hout, P.J., Spaans, B., Dekinga, A., Brugge, M. & Piersma, T. (2013) Toxin constraint explains diet choice, survival and population dynamics in a molluscivore shorebird. Proceedings of the Royal Society B-Biological Sciences 280: 20130861. 
Leyrer, J., Lok, T., Brugge, M., Spaans, B., Sandercock, B.K. & Piersma, T. (2013) Mortality within the annual cycle: seasonal survival patterns in Afro-Siberian red knots. Journal of Ornithology 154: 933-943. 
Lok, T., Overdijk, O. & Piersma, T. (2013) Migration tendency delays distributional response to differential survival prospects along a flyway. American Naturalist 181: 520-531. 
Piersma, T., Van der Velde, M., El-Hacen, H.M., Lok, T., Overdijk, O. (2012) Molecular verification of the subspecies status of the Mauritanian spoonbill Platalea leucorodia balsaciArdea 100: 131-136. 
Leyrer, J., Lok, T., Brugge, M., Dekinga, A., Spaans, B., Van Gils, J.A., Sandercock, B.K. & Piersma, T. (2012) Small-scale demographic structure suggests preemptive behavior in a flocking shorebird. Behavioral Ecology 23: 1226-1233. 
Lok, T., Overdijk, O., Tinbergen, J.M. & Piersma, T. (2011) The paradox of spoonbill migration: most birds travel to where survival rates are lowest. Animal Behaviour 82: 837-844. 
van de Pol, M., Ens, B.J., Heg, D., Brouwer, L., Krol, J., Maier, M., Exo, K.M., Oosterbeek, K., Lok, T., Eising, C.M. & Koffijberg, K. (2010) Do changes in the frequency, magnitude and timing of extreme climatic events threaten the population viability of coastal birds? Journal of Applied Ecology 47: 720-730. 
Vahl, W.K., Lok, T., van der Meer, J., Piersma, T. & Weissing, F.J. (2005) Spatial clumping of food and social dominance affect interference competition among ruddy turnstones. Behavioral Ecology 16: 834-844. 
Other publications
Lok, T. (2013) Spoonbills as a model system: a demographic cost-benefit analysis of differential migration. PhD thesis. University of Groningen. 
Lok, T., Overdijk, O., Horn, H. & Piersma, T. (2009) The Spoonbill Platalea leucorodia population of the Wadden Sea islands: does population growth level off? Limosa 82: 149-157.


Professional education

2013           PhD, University of Groningen, cum laude (Promotors: Prof. Dr. Theunis Piersma and Prof. Dr. Joost Tinbergen). Thesis title: Spoonbills as a model system: a demographic cost-benefit analysis of differential migration.

2005           M.Sc. Evolutionary Biology (Topmaster programme), University of Groningen, cum laude

2003           B.Sc. Biology, University of Groningen


Awards and prizes

2018: NWO Veni award. The ontogeny of migration: an interplay of genes and environment (250 k€)

2015: NWO Rubicon award. The adaptability of migratory animals to a rapidly changing world: novel measures from an integrated analysis of count, mark-recapture and telemetry data. (110 k€)

2014: Van Swinderen prize (2nd place) for best Dutch summary of a PhD-thesis at University of Groningen

2008: NWO Open Aanvraag. Fitness consequences of migration in the spoonbill: a comparative approach.  (175 k€)



For more information about me and my research, see my personal website 

Linked news

Monday 16 July 2018
2 Veni-financieringen voor NIOZ-onderzoekers | 2 Veni grants for NIOZ researchers
[Scroll down for English version] De Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) heeft twee veelbelovende NIOZ wetenschappers een Veni-financiering van 250.000 euro toegekend. Hiermee kunnen zij gedurende drie jaar hun eigen…

NIOZ publications