Disease exposure and immune investment in the annual cycle of pink-footed geese
Keywords
Annual cycle, body condition, ecological immunology
General Context
Investment in immune defences represents a trade-off – while greater investment may infer greater protection to disease and hence greater survival, this investment simultaneously entails significant costs to the individual. One way to minimise the cost of maintaining an immune system and maximise protection from infection would be to adaptively invest in immune defences in response to the local parasite pressure (i.e. when they need to) and food availability (i.e. when they can afford to). Long distance migrants, like pink-footed geese, over-winter in more disease-prone areas (in the temperate zone), but breed in the ‘disease-free’ arctic. We are interested in whether these migrants, passing through areas with very different disease pressure, can be seen to adaptively manage their immune investment.
Project outline
Based on immune measures from blood smears and plasma of 300 pink-footed geese just prior to their northward spring migration and again after their chicks have hatched in late summer, we aim to compare immune investment throughout the annual cycle. We would then compare this immune investment in relation to disease pressure (based on location) and affordability (based on individual and population condition estimates as well as seasonal survival in the population).
Remarks
Field sampling was conducted in Denmark and Svalbard in 2007 and again in 2009. This project involves laboratory-based analysis of immunocompetence.
Duration
6-9 months
Contact
Quantifying the cost of an immune response in Bewick’s swans
Keywords
Phytohemagglutinin, metabolic cost, foraging, ecological immunology
General Context
There is great interest in the role disease plays in the ecology of wild animals, particularly how infection might reduce an animal’s ability to respond to future events. However, it is difficult to generalise about the effect of disease in wild populations. Natural infections may not occur at random thus any observed differences may be cause of infection rather than an effect. Also, different diseases affect animals from different habitats, and so experiments using a particular disease may not be widely generalisable. To overcome this, a number of studies have used so-called “benign immune challenges” – dosing animals with compounds that elicit an immune response but are both novel to the animals and not disease causing.
Project outline
This project will examine the response of captive birds to an immune challenge, called phytohemaglutinin. We will examine the metabolic and behavioural changes induced by this immune challenge in Bewick’s swans, as well as whether the strength of the immune response is related to the costs incurred.
Remarks
This project involves both animal experiments in captivity and a few simple immune analyses in the laoratory.
Duration
3-4 months
Contact
Avian influenza infection and its effect on foraging, movement, condition, and success in Bewick’s Swans
Keywords
Avian influenza, migratory preparation, site fidelity, breeding attempt, disease ecology
General Context
Observational studies have shown that individual swans infected with influenza forage at slower rates, accumulate energy stores slower, and migrate later and less far than non-infected counterparts. These dramatic departures from ‘normal’ behaviour are of great importance to understanding both the role wild birds play in the ecology of diseases and the role disease plays in the ecology of their hosts. However, naturally infected individuals may have been poor quality to start with (and hence became infected). Conversely, individuals may have become infected at random, and experienced a decline in condition as a result. Hence an experimental approach is needed to address the question of infection costs in wild birds.
Project outline
Last winter we started a field experiment to examine whether infection might alter Bewick’s swans foraging and fuelling for migration, their migration path and timing, and their breeding behaviour. 24 individually marked female swans, each fitted with a GPS logger, will return to the Netherlands in October. The first half of this project involves downloading and analysing the GPS data stored by these swans, with information on their migration and breeding. The second part of the project involves conducting behavioural protocols and downloading information on winter movements from birds we plan to capture in the coming winter.
Remarks
The project requires a keen interest in working outdoors. It involves extensive fieldwork throughout the winter to download GPS data and conduct behavioural observations on individual swans. A driver’s license is extremely useful.
Duration
4-6 months (Starting October 2009). Two positions available.
Contact
External transport potential of freshwater snails by birds
Key words:
Experiment, freshwater snails, transport, external
General context
New ponds and wetlands are often colonized rapidly by all kinds of small aquatic organisms. This suggests these organisms can easily disperse across land between suitable habitat, despite that a lot of species can hardly survive out of the water and certainly not move across land on their own. However, they are frequently found in new wetlands, desert oases and are often widespread around the world. How do they get there?
A suggestion already proposed by Darwin is that some aquatic organisms can “hitch-hike” passively on flying waterfowl. If species can attach to feathers, feet or bills of birds that fly between ponds, or are eaten by birds but not fully digested, long distance transport becomes very likely. Birds (that can fly up to 70 km/h) rapidly cover distances that many aquatic organisms can never achieve by themselves. For many wetland plants seeds it has been shown that they can survive gut passage of ducks, and are excreted viably after several hours leading to considerable dispersal distances. More recently, species like daphnia’s and brine shrimps have also been found to be transported by birds. Because much of the evidence is still anecdotal and needs further investigation, my PhD project focuses on several aspects of this bird-mediated dispersal, thereby using freshwater snails as model species.
Project outline
To determine the potential of waterbirds to transport freshwater snail species externally between ponds, we will perform an experiment with Mallards moving between simulated ponds. The question is to what extend propagules are able to attach to birds, and what kind of structure or situation is needed in the field before a seed or snail get’s attached to a bird. In an experimental environment with isolation cages filed with water, we can create different environments birds might encounter in the field: we can simulate wetlands that contain snails, seeds or water plants in different quantities; make a structure with different water plants facilitating propagules to attach to birds; vary time that birds are in the cages to quantify how many propagules attach in a given time; vary the kind of propagule, or vary all kinds of factors that might help propagules to attach to birds. The question is in which situation propagules are attaching to a bird. This is a flexible project, anyone interested can adjust it according to own ideas, we have already have approval of the ethics committee to perform this kind of experiment.
Duration (indicative)
4-6 months, starting August 2009 or later
Contact
Freshwater snail characteristics and their potential to be dispersed by birds
Key words
bird-mediated dispersal, freshwater snails, species characteristics, experiments
General context
New ponds and wetlands are often colonized rapidly by all kinds of small aquatic organisms. This suggests these organisms can easily disperse across land between suitable habitat, despite that a lot of species can hardly survive out of the water and certainly not move across land on their own. However, they are frequently found in new wetlands, desert oases and are often widespread around the world. How do they get there?
A suggestion already proposed by Darwin is that some aquatic organisms can “hitch-hike” passively on flying waterfowl. If species can attach to feathers, feet or bills of birds that fly between ponds, or are eaten by birds but not fully digested, long distance transport becomes very likely. Birds (that can fly up to 70 km/h) rapidly cover distances that many aquatic organisms can never achieve by themselves. For many wetland plants seeds it has been shown that they can survive gut passage of ducks, and are excreted viably after several hours leading to considerable dispersal distances. More recently, species like daphnia’s and brine shrimps have also been found to be transported by birds. Because much of the evidence is still anecdotal and needs further investigation, my PhD project focuses on several aspects of this bird-mediated dispersal, thereby using freshwater snails as model species.
Project outline
In this project we would compare the potential for bird-mediated dispersal between different freshwater snail species, and relate this potential to their actual geographic distributions. Data on geographic range size for different snail species is available: some are widespread, some are limited to only a small area. We would start with collecting different snail species from ponds in the Netherlands and experimentally determining their characteristics like desiccation tolerance, pH tolerance, temperature tolerance, etc. Combined with additional available information from the literature, this can form a database of species that are potentially good candidates for bird-mediated dispersal. This can then be compared to the distributions of these different species: we would expect a positive relation between tolerances to the environment and range sizes of the different species across their suitable habitats.
Duration (indicative)
4-6 months, starting August 2009 or later
Contact
Can bird distributions explain freshwater snail distributions?
Key words
GIS, spatial analyst, distributions, comparison, freshwater snails, waterbirds
General context
New ponds and wetlands are often colonized rapidly by all kinds of small aquatic organisms. This suggests these organisms can easily disperse across land between suitable habitat, despite that a lot of species can hardly survive out of the water and certainly not move across land on their own. However, they are frequently found in new wetlands, desert oases and are often widespread around the world. How do they get there?
A suggestion already proposed by Darwin is that some aquatic organisms can “hitch-hike” passively on flying waterfowl. If species can attach to feathers, feet or bills of birds that fly between ponds, or are eaten by birds but not fully digested, long distance transport becomes very likely. Birds (that can fly up to 70 km/h) rapidly cover distances that many aquatic organisms can never achieve by themselves. For many wetland plants seeds it has been shown that they can survive gut passage of ducks, and are excreted viably after several hours leading to considerable dispersal distances. More recently, species like daphnia’s and brine shrimps have also been found to be transported by birds. Because much of the evidence is still anecdotal and needs further investigation, my PhD project focuses on several aspects of this bird-mediated dispersal, thereby using freshwater snails as model species.
Project outline
In this project we would like to compare freshwater snail distributions to bird distributions using GIS. Our hypothesis is that birds are important vectors dispersing freshwater snails between wetlands, and we therefore expect a higher snail species diversity in areas with higher bird densities. We would collect available information about bird densities in Europe or part of Europe and compare this to information about snail densities in the same areas. If we can find a potential role of birds, we can potentially identify which bird species are specifically important for dispersal, and which snail species are best at dispersal by birds. This would finally explain the fast colonization rates of aquatic snails to remote areas, and their wide distributions around the world.
Duration (indicative)
4-6 months, starting August 2009 or later
Contact
Climate change: Are migration costs reduced for arctic breeding geese? Modelling energy expenditure during flight and staging
Key words
Stochastic dynamic model; flight performance; bird migration.
General context
Pink-footed goose, an Arctic breeding geese species, migrates yearly from their wintering grounds in Belgium and the Netherlands to their breeding grounds on Spitsbergen and the Svalbard archipelago. During their migration, they stage on a number of stop-over sites in Denmark and Norway where they refuel for their next migratory step. The timing of arrival and state at arrival play a crucial role in determining their breeding success. Thus, what geese experience during migration and which conditions they encounter on stop-over sites crucially influences fitness and finally population dynamics.
Project outline
In the course of changing climatic conditions, the energy geese have to expend during flight, i.e. the migration itself, and when staying on stop-over sites might change with temperature and wind conditions. How geese cope with such altered energetic demands will be investigated in this project. In a first step, we will quantify the dependence of energy expenditure during staging on changing climate variables, e.g. temperature and precipitation. The specific tasks will be an overview of existing knowledge and a prediction of the trend according to climate change scenarios. In a second step, we will focus on energy expenditure during flight. This is supposed to depend primarily on wind conditions, i.e. speed and direction, which will therefore be varied according to the expectations from the above-mentioned climate change scenarios.
Remark
Some experience with programming or modelling would be helpful.
Duration (indicative)
3 - 6 Months, starting date to be arranged.
Contact
Marcel Klaassen (e-mail: m.klaassen@nioo.knaw.nl; tel.: +31 (0)294 239 317).
Goose migration: How much do they gain when staging on different habitats? Meta-analysis of gain functions on goose stop-over sites
Key words
Goose migration; foraging; meta-analysis; gain functions; vegetation quality.
General context
Arctic breeding geese migrate yearly from their wintering grounds in Belgium and the Netherlands to their breeding grounds on Svalbard. During their migration, they stage on various stop-over sites where they refuel for their next migratory step. The timing of arrival and state at arrival play a crucial role in determining their breeding success. Thus, what geese experience during migration and which conditions they encounter on stop-over sites crucially influences fitness and finally population dynamics. Previous studies have already shown that the gain functions, i.e. the temporal availability of food and its energetic quality, crucially determine migratory decisions. Therefore, a sound knowledge and quantification of the gain functions will provide an important basis for understanding of migration decisions in these and other Arctic-breeding geese.
Project outline
This project aims at integrating various empirical investigations into a general framework. Herein, gain functions for different staging sites and goose species, e.g. Pink-footed goose, Barnacle goose, Brent goose, and others, shall be derived from earlier empirical research on feeding observations and abdominal profile estimations.
Duration (indicative)
3 - 6 Months, starting date to be arranged.
Contact
Marcel Klaassen (e-mail: m.klaassen@nioo.knaw.nl; tel.: +31 (0)294 239 317).
Goose migration: Impacts of climate and land use changes on migration schedules of Barnacle geese
Key words
Goose migration; foraging; climate change; land use change; future scenarios.
General context
Arctic breeding geese migrate yearly from their wintering grounds in Belgium and the Netherlands to their breeding grounds on Svalbard. During their migration, they stage on various stop-over sites where they refuel for their next migratory step. The timing of arrival and state at arrival play a crucial role in determining their breeding success. Thus, what geese experience during migration and which conditions they encounter on stop-over sites crucially influences their fitness and finally determines population dynamics.
Over the past decades, climate and land use along the flyway of these geese have changed dramatically. The question, how changes in the past have led to migration patterns that we observe nowadays, plays a key role when we aim to predict the consequences of potential future developments.
Project outline
In the project, a stochastic dynamic model for goose migration will be used to estimate the consequences of past and potential future climate and land use changes. To this aim, we will proceed in two steps: 1) use past climate and land use data to explain variation in past migration schedules and 2) use future scenarios of climate and land use change to estimate the consequences of such changes for the geese.
Duration (indicative)
6 Months, starting date to be arranged.
Contact
Marcel Klaassen (e-mail: m.klaassen@nioo.knaw.nl; tel.: +31 (0)294 239 317).
Birds as seed dispersers: gut transition time during flight
Key words
Endozoochorous dispersal; Gut functioning; Flight.
General context
Many organisms, but notably plants, make use of animals to disperse their seeds. It has even been argued that these propagules may potentially be transported over hundreds of kilometers in the guts of migratory birds. A major problem in all studies so far is the assumption that the functioning of the birds' guts remains similar while stationary and in flight. Thus it is being assumed that the rate of passage and the viability of passed seeds is similar in inactive and flying birds. This seems a rather unrealistic assumption to me. I hypothesize that transition time of seeds ingested just before flight is much longer and viability much higher than in stationary, inactive, birds.
Project outline
In a first step small indigestible particles will be fed to birds that will subsequently be flown. After flight, the droppings will be collected at regular time intervals to check for the presence of the markers. In the experiments the time between feeding the markers and flight onset, as well as the duration of the flight, will be varied. In a second step seeds will be fed to the birds and their viability checked.
Duration (indicative)
6 Months.
Contact
Marcel Klaassen (e.mail: m.klaassen@nioo.knaw.nl; tel.: +31 (0)294 239 317).
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