Foraging distribution of Lesser Black-backed Gull (Larus fuscus) in a changing landscape

Alejandro Sotillo¹, Eric Stienen², Liesbeth de Neve¹ and Luc Lens¹

¹ Terrestrial Ecology Unit, Ghent University, Ghent, Belgium

² Research Institute for Nature and Forest (INBO), Brussels, Belgium

The Lesser Black-backed Gull (Larus fuscus) colonized and quickly proliferated in the Belgian Coast during the second half of the 20^th Century. The Belgian L. fuscus breeding population is highly dependent on human-generated sources of food: fishery discards are crucial during the chick rearing stage of the breeding season, and garbage is exploited throughout the year. The prospect of a strong drop in both the production of discards and the availability of garbage in the near future brings up the question on which responses can be expected from local breeding Lesser Black-backed Gulls in terms of habitat use and feeding patterns.

To answer this question, the Terrestrial Ecology Unit of Ghent University is studying the current habitat use patterns and food dependencies of Belgian L. fuscus breeding individuals, using a combination of GPS tracking, stable isotope analysis and captivity chick rearing experiments. Assessing foraging habitat use as a function of resource distribution, foraging costs and food demands of the breeding population, will set the base for predictions of redistribution of foraging effort, or resettlement of breeders as a consequence of the disappearance of one or more main sources of food.

 

Parental strategies in a changing world – How intrinsic and extrinsic factors impinge on parental care in Lesser Black-backed Gulls

Marwa Kavelaars^1,2, Luc Lens² and Wendt Müller¹

¹ Behavioural Ecology and Ecophysiology Group, University of Antwerp, Antwerp, Belgium

² Terrestrial Ecology Unit, Ghent University, Ghent, Belgium

Parental care increases offspring survival, but comes at a cost for the parents. Parents therefore face a trade-off between increased investment in current or future reproduction, and have to take numerous factors into account to optimise their decisions. My research focuses on these parental strategies, and addresses how reproductive decisions are related to environmental variation in food accessibility, how individual specialisation in resource use constraints parental care, and how individual decisions depend on the partner. I study this in a wild population of individually marked Lesser Black-backed Gulls, a long-lived migratory seabird with a high level of inter-individual variation in resource use and make use of UvA-BiTS GPS devices that allow detailed measurements of parental effort and parental decision rules.

 

Consistency, diversity and connectivity in migration strategies of an omnivorous seabird

Judy Shamoun-Baranes¹, Kees Camphuysen², Viola Ross-Smith³, Chris Thaxter³, Joey Burant¹, Emiel van Loon¹ and Willem Bouten¹

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

² Royal Netherlands Institute for Sea Research (NIOZ),  Texel, The Netherlands.

³ British Trust for Ornithology (BTO), Norfolk, United Kingdom

For many species, migration is an essential adaptation for living in seasonal environments.   Yet migration strategies need not be equal among members of a population.  The Lesser Black-backed Gull is an omnivorous seabird whose ecology has been changing over the last decades.  We compare the migration strategies and connectivity of adults tracked using GPS over multiple years, from breeding populations in coastal regions of north-western Europe.  A broad range of migration strategies co-exists within these populations, from long distance migration of 5000 km to Mauritania, to migratory distances of only 150 km.  Individuals are very consistent in their migration routes and site faithful at the fine scale between years.   This species exploits a broad range of habitats in the winter and we identify several sites in western Europe that support connectivity between the populations during the non-breeding season.

 

Studying the impact of disturbance and carry-over effects in Oystercatchers

Bruno Ens¹, Adriaan Dokter², Judy Shamoun-Baranes², Emiel van Loon², Roeland Bom³, Willem Bouten², Kees Oosterbeek¹, Martijn v.d Pol⁴, Eelke Jongejans⁵ and Hans de Kroon⁵

¹SOVON Dutch Centre for Field Ornithology, Texel, The Netherlands

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

³ Royal Netherlands Institute for Sea Research (NIOZ),  Texel, The Netherlands.

⁴ Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands

⁵ Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, The Netherlands

In a previous study on the tidally changing distribution of  foraging Oystercatchers (Haematopus ostralegus) employing UvA-BiTS, we characterized different behaviours using accelerometer data, discovered unsuspected partial migration in our coastal study population and were able to relate low tide foraging areas to roosting sites in different parts of the Wadden Sea. As part of our new research project CHIRP (Cumulative Human Impact on biRd Populations), we aim to employ UvA-BiTS to study the impact of disturbance from military exercises on the time- and energy budget during the non-breeding season. We hope to subsequently obtain information on the behaviour during the breeding season of the tagged birds to see if there are carry-over effects from disturbance during the previous non-breeding season.

 

Using acceleration data to track how migratory geese fuel for reproduction

 Thomas Lameris^1,2,3, Willem Bouten², G. Eichhorn¹, F. Engelman¹, Henk van der Jeugd³ and Bart Nolet^1,2

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

² Institute for Biodiversity and Ecosystem Dynamics, UvA, Amsterdam, the Netherlands

³ Vogeltrekstation Dutch Centre for Avian Migration and Demography, NIOO-KNAW, The Netherlands

Migratory birds breeding in the Arctic, where the summer is short, have to start breeding early in the season when little food is available. Birds can cope by bringing the body reserves necessary for egg production with them from wintering and migration stopover sites. Barnacle Geese breeding in Arctic Russia have accelerated their spring migration by skipping stopover sites and flying in an almost direct flight to the breeding grounds. Can these birds bring enough body reserves to the breeding grounds, or have they become dependent on local food resources?

We use acceleration data from spring migration tracks to determine locations where Barnacle Geese are grazing, and analyze resource acquisition before breeding. By comparing these data with stable isotope signatures taken from the geese’ offspring, reflecting the resource from which the egg is created, we can quantify whether geese differing in migration schedules use different resources to produce their eggs.

 

Dawn ascents to astonishing altitudes during migration of Eleonora’s Falcons (Falco eleonorae)

Willem Bouten¹, Laura Gangoso², Adriaan Dokter¹, Judy Shamoun-Baranes¹, Duarte Viana² and Jordi Figuerola²

¹ Institute for Biodiversity and Ecosystem Dynamics, UvA, Amsterdam, the Netherlands
² Doñana Biological Station, Spanish National Research Council (CSIC), Seville, Spain

Eleonora’s Falcons, breeding on the Canary Islands and wintering on Madagascar revealed astonishing dawn ascents: steep vertical movements, occasionally up to 5500 m above ground level. We evaluated various possible motivations for such behaviour, using high resolution GPS tracking and flight modes monitored with a tri-axial accelerometer. Birds used flapping flight  to climb with vertical speeds of 0.8-1.2 m/s, starting at 0.5-1 hour before sunrise although these ascents require more than twice as much power as horizontal flapping flight. Dawn ascents mainly occurred along the magnetic equator (where magnetic inclination is zero) but not in mountainous areas where landmarks are clearly visible above the landscape. We concluded that this mainly diurnal migrant seeks a wide overview of the landscape to calibrate the map with visual cues on compass information obtained from polarized light and the rising sun, especially along the magnetic equator.

 

Seasonal niche-shifts of a long-distance migratory raptor revealed through a movement-based approach

Rafa Silva¹, Laura Gangoso¹, Duarte Viana¹, Jordi Figuerola¹, Javier Bustamante¹ and Willem Bouten²

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

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

The adult life of an organism can broadly be divided into reproductive and non-reproductive stages. The transition between the two often entails profound phenotypic changes. Seasonal changes in energy demands, food availability, and habitat type across regions might cause concurrent changes in foraging behavior to optimize its efficiency in each particular case. Here, we investigated the shift in foraging behavior of the long-distance migratory Eleonora’s falcon (Falco eleonorae) from a movement ecology perspective. This raptor breeds on islands over the Mediterranean basin, where it takes advantage of the flux of migratory birds to rear offspring, and winters in Madagascar, where it feed mainly on insects. We showed that foraging behavior and flying performance of Eleonora’s falcons markedly differed between seasons.

 

Movement ecology and behaviour of Canarian Egyptian vultures

Marina García Alfonso¹, José  Antonio Donazar¹, David Serrano¹, Laura Gangoso¹

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

Vultures are long-lived, threatened birds with deferred maturity which often perform wide-ranging movements. However, their movement ecology during the pre-breeding stage is a major knowledge gap that largely precludes the application of evidence-based conservation measures.
The aim of our research is to deepen into the movement ecology of Canarian Egyptian vultures (endemic subspecies inhabiting some Canary Islands) during the pre-breeding stage and to relate it with the availability and predictability of resources and ecological constraints susceptible of being managed. For such purpose, we will analyse individual consistency in the use of feeding resources (farms, vulture restaurants) and roosting sites (power lines). We also aim to study breeding recruitment in relation to pre-breeding movement patterns. Currently, we are tracking 47 individuals (27 UvaBiTS + 20 e-obs devices) and we have collected more than 12.5 million of fixes.