Abstracts presentations



Mastering migration: unravelling the ontogeny of strategic migratory detours in European Honey Buzzards Pernis apivorus

Wouter M.G. Vansteelant1, Judy Shamoun-Baranes1, Jan van Diermen2, Willem van Manen2, Patrik Byholm3 and Willem Bouten1

1 Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands

2Treetop Foundation, Assen, the Netherlands

3 Novia R&D, Novia University of Applied Sciences, Finland

Migration routes are a highly flexible feature of avian migration. Routes may vary between species, populations and individuals. Even individuals may exploit alternative routes in consecutive years. Given that migration routes are so flexible it seems unlikely that the development of these routes is governed by genetic factors alone. Inexperienced juveniles probably assimilate individual strategies over time, based on the conditions encountered, early-life experiences and social information.

In this presentation we unravel the development of complex individual migration routes for 30 Honey Buzzards which were tracked from fledging till adulthood. We demonstrate how wind conditions during the first autumn migration influences the longitude at which birds settle wintering sites and routes used for return migration. Moreover, we show that birds learn safer routes with age, first by gradual improvements of individually learnt routes, only later by following experienced adults along strategic detours. We conclude that life-history traits such as longevity play a major role in migratory development of Honey Buzzards, and probably many other species.


Deteriorating ecological conditions during wintering – how Montagu’s Harriers cope with Moreau’s Paradox

Almut E. Schlaich* 1,2,3, Raymond H.G. Klaassen1,2, Willem Bouten4, Vincent Bretagnolle3, Ben J. Koks1, Alexandre Villers3 and Christiaan Both2

1 Dutch Montagu’s Harrier Foundation, Scheemda, The Netherlands

2 Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands

3 Centre d’Etudes Biologiques de Chizé, Université de la Rochelle, Beauvoir-sur-Niort, France

4 Institute for Biodiversity and Ecosystem Dynamics ,University of Amsterdam, Amsterdam, The Netherlands

The hundreds of millions of Afro-Palearctic migrants wintering in the Sahel have to prepare for spring migration at the end of a long dry winter period, thus when ecological conditions are worst (Moreau’s Paradox). Montagu’s Harriers Circus pygargus spend six months of the year in their wintering areas in the Sahel. At their last wintering site, birds have to stay even if conditions are deteriorating, because they cannot move further south being already at the southern edge of the Sahelian zone. We combined high-resolution GPS-tracking data of individual harriers with field data on prey availability to show that ecological conditions indeed deteriorate towards the end of their wintering period (decreasing vegetation greenness and grasshopper biomass) and that individual birds behaviorally respond to those changes. Harriers increased their flight time during the second half of the winter, thereby flying more and even departing later when wintering in drier areas.


Large-scale dispersal services provided by migratory birds

Duarte Viana1, Laura Gangoso1, Willem Bouten2 and Jordi Figuerola1

1 Doñana Biological Station, Spanish National Research Council (CSIC), Seville, Spain

2 Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands

Two centuries ago, Darwinalreadyproposed that migratory birds are involved in the long distance dispersal of many organisms. However, long distance dispersal is considered to be a stochastic process that cannot be directly quantified. This outstanding phenomenon can only be addressed by combining different disciplines, including biogeography, movement ecology, and meteorology. Here, we took advantage of the natural hunting “service” provided by the Eleonora’s falcon to sample migratory birds, and used last-generation tracking technology to verify that those birds were hunted by falcons overseas during active migration. We showed for the first time that migratory birds disperse seeds from mainland onto oceanic islands over hundreds of kilometres. Up to 1.2% of birds that reached the Canary Archipelago during their autumn migration carried seeds in their guts, likely resulting in the transport of millions of seeds due to the billions of birds making seasonal migrations each year.


Herbivores fuelling for migration: prisoners or masters of their food supply?

A.M. Dokter 1,4, W. Fokkema 2, W. Bouten 4, B.S. Ebbinge 3, B.A. Nolet 1, H. Olff 2 and H.P. van der Jeugd 1

1 Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands

2 Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands

3 Team Animal Ecology, Alterra, Wageningen-UR, Wageningen, The Netherlands

4 Institute for Biodiversity and Ecosystem Dynamics ,University of Amsterdam, Amsterdam, The Netherlands

Unlike other goose species, Brent Geese are well adapted to foraging in intertidal and marine environments. In recent years, Brent have increasingly made use of agricultural land. To understand these habitat shifts, and given that the intertidal ecosystems that Brent traditionally rely on are world-wide in decline, it is crucial to understand the habitat selection and energetics of foraging Brent throughout their annual cycle. We equipped 30 Brent staging in agricultural and saltmarsh habitats with uva-bits loggers in spring. Combining high-resolution GPS-tracking, acceleration-based behavioural classification, thermoregulation modelling, and measurements of food digestibility and intake rates, we reconstructed their energy budgeting in detail. Individual fuelling trajectories were used to identify factors that explain differences in fuelling rates. Do migratory strategies of ‘saltmarsh’ and ‘pasture’ birds differ? Does their behaviour change on these different spring habitats? And what do we learn from this comparative analysis about the future habitat use and requirements of this species?


Movements of crab plovers Dromas ardeola under different food conditions

Roeland A. Bom1,2, Willem Bouten3 and Jan A. van Gils2

1 Royal Netherlands Institute for Sea Research (NIOZ),  Texel, the Netherlands.

2 Remote Sensing and GIS Center, Sultan Qaboos University, Al Khod, Oman

3 Institute for Biodiversity and Ecosystem Dynamics ,University of Amsterdam, Amsterdam, The Netherlands

In Barr al Hikman, Sultanate of Oman, crab plovers Dromas ardeola feed on either swimming crabs or burrowing crabs. These two prey species live in different. Moreover both crab species demand different hunting techniques from the crab plover. Using GPS data we study how crab plovers change their habitat use and with accelerometer data we studied the hunting behaviour in two winters in which swimming crab densities changed from highly abundant to nearly absent and burrowing crabs densities remained the same. In the rich swimming crab year, crab plovers were seen to spend less time on foraging, but foraging more in the waterline. In the swimming crab poor year crab plovers had to spend more time foraging which they did on the exposed mudflats where they adopted a more sit-and-wait hunting strategy.


Linking foraging strategy to ocean productivity in tern species:proof of concept and first data.

Jill Shephard1, Nic Dunlop2, Alan Pearce3, Peter Fearns3, Willem Bouten4

1. School of Veterinary and Life Sciences, Murdoch University, WA.

2. Conservation Council of Western Australia

3. School of Science, Curtin University, WA.

4. Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, the Netherlands.

 It is proposed seabirds may have an important role as bioindicators of climate and ocean condition. Seabirds are closely linked to marine foodwebs, and foodweb stability is strongly dependent on ocean condition. Within Australia, the El Niño Southern Oscillation (ENSO) is the strongest driver of natural climate variation across years. Extreme El Niño events can have devastating effects on seabird survivorship, as fish move from their usual ranges to cope with changing ocean temperatures. In the face of continued oceanic change, it is therefore vital to develop new bio-indicators to serve as tools in fishery and biodiversity management. In this study we use GPS telemetry and remote sense data to determine if seabird foraging strategies can be linked to areas of ocean productivity. Here we present preliminary data on two species of dark tern from Western Australia tracked during different stages in the breeding season.


Marine versus freshwater foraging by breeding Eurasian spoonbills

Matthijs van der Geest1, Thomas Oudman*,1,2, Tamar Lok1, Petra de Goeij2, Willem Bouten3, Camilla Dreef3 and Theunis Piersma1,2

1 Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands

2 Royal Netherlands Institute for Sea Research and Utrecht University(NIOZ), Texel, The Netherlands

3 Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam,  Amsterdam, The Netherlands

Since their near extinction in the 70’s, the Dutch population of spoonbills Platalea leucorodia has been growing exponentially. Colonies were established on all Wadden Sea islands. Most of these are now stabilizing, but overall growth in the Netherlands remains exponential, with many growing colonies on the mainland, also in freshwater environments. Do spoonbills prefer marine foraging habitats? 13 spoonbills were followed with the UvA bird tracking system during three consecutive breeding seasons in a Wadden Sea island colony. This revealed the range of foraging areas used by individual birds in space and time, significant differences in the use of marine versus freshwater habitats in the course of the breeding period and between the sexes. These insights may help to explain the spatial pattern of the spoonbills breeding range expansion.


Tracking lesser black-backed gulls from three colonies unravels the extent of seabird-wind farm interactions through the year

Chris B. Thaxter1, Viola H. Ross-Smith1, Willem Bouten2, Nigel A. Clark1, Greg J. Conway1, Elizabeth A. Masden3, Lee Barber1, Gary Clewley1 and Niall H.K. Burton1.

1 British Trust for Ornithology (BTO), Norfolk, United Kingdom

2 Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands

3 Environmental Research Institute, University of the Highlands and Islands, Thurso, United Kingdom

Marine and terrestrial environments are under increasing pressure from human activities, including renewable energy developments. We investigated the movements of Lesser Black-backed Gulls from three breeding colonies (Orford Ness, Walney and Skokholm) through the year in relation to offshore and onshore wind farms. We (1) briefly review previous work at Orford Ness showing how movements and risks posed by wind farms during the breeding season vary within and between years. We (2) briefly outline findings from Walney showing how high-resolution GPS data are informing understanding of three-dimensional behaviour within operational wind farms. Finally, we investigate (3) movements of birds, quantifying colony-specific relative exposure through the year. This study is providing evidence of seabird-wind farm interactions to better inform understanding of potential wind farm impacts.


Bird inspired unmanned air vehicles

Shane Windsor1, Cara Williamson1, Nick Durston1 and Emily Shepard2

1 Department of Aerospace Engineering, University of Bristol, Bristol, United Kingdom
2 Department of Biosciences, Swansea University, Swansea, United Kingdom

The agile and efficient flight of birds shows what flight performance is physically possible, and in theory could be achieved by unmanned air vehicles (UAVs) of the same size, flying in the same conditions. Recently we have measured the fine scale flight patterns of gulls in relation to the wind field around sea-front buildings using laser range finder based tracking methods and computational fluid dynamics modelling.  We found that the gulls varied their position to select a narrow range of updraught values rather than exploiting the strongest updraughts available and their precise positions were consistent with a strategy to increase their velocity control in the face of cross wind gusts, and therefore mitigate risks.  These results are complimentary to our on going work developing novel bio-inspired sensor arrays for flight control in UAVs inspired by how birds “feel” the airflow over their wings and work studying the aerodynamics of birds in flight.  By understanding how birds are adapted to interact with air flows at both a morphological and behavioural level, we hope to gain inspiration for the development of novel flight control strategies and technologies for UAVs.


When the gulls come to town

Eric Stienen1, Roland-Jan Buijs2, Wouter Courtens1, Peter Desmet1, Francisco Hernandez3, Marwa Kavelaars4, Luc Lens5, Hans Matheve5, Wendt Müller4, Alejandro Sotillo5, Marc Van de walle1, Nicolas Vanermen1, Hilbran Verstraete1

1Research Institute for Nature and Forest (INBO), Brussels, Belgium

2Buijs Eco Consult B.V., Oud-Vossemeer, The Netherlands

3Flanders Marine Institute (VLIZ), Ostend, Belgium

4Ethology (ETHO), University of Antwerp,  Antwerp, Belgium

5Terrestrial Ecology Unit (TEREC), Ghent University,  Ghent, Belgium

Throughout Europe, many natural breeding colonies of ground-nesting Larus-gulls strongly decreased in numbers or even became deserted during the past decades. The opportunistic gulls often moved to industrialized and urbanized sites where they frequently come into conflict with humans. The strong increase in urban gull populations is thought to be linked to the presence of predator-free nesting sites (notably roof-tops) in combination with a high availability of food in the form of food wastes or takeaways discarded by tourists. In coastal communities the general perception prevails that the roof-nesting gulls become increasingly aggressive and survive by snatching food from unsuspecting tourists. There are, however, very few studies that show where urban gulls are collecting their food and whether or not this behavior can sustain the urban populations. Therefore we mounted UvA-BiTS gps-trackers on 75 Lesser Black-backed Gulls and 26 Herring Gulls breeding at the Belgian and Dutch coast. Here we report on the foraging behavior of these gull and specifically focus on the use of urban environments. Our study shows that although both gull species are considered to be true generalists, individuals within the population often show extreme specialism with respect to both foraging behavior and habitat use. Only a minority of the roof-nesting gulls actually did use the urban environment for foraging and not all gulls specialized in food snatching actually nest in the urban environment. This has important implications for the management of gull nuisance which in Belgium currently targets the entire roof-nesting population.