Health of arctic and antarctic bird populations

The Plan

Summary - Infections affect the fitness of wild animals and thus play an important role in structuring animal populations. This study will quantify geographic variation in the prevalence of pathogens and parasites in wild arctic breeding, individually marked birds. The effect of these infections on parameters of individual fitness like survival, reproduction and behaviour will be assessed through correlation and through experimentation using medical treatment against infections. The potential susceptibility of individuals to future infections will be tested by challenging the immune system. The project should develop into an international circumpolar investigation in the International Polar Year 2007-2008.

Introduction Infections lead to an activation of the immune system and a physiological battle to regain health. This process is energy demanding and usually reduces the ability of an individual to perform normal duties (Lochmiller & Deerenberg. Oikos 88: 87-98). During the breeding season wild migratory birds are operating under maximum energy requirements to produce offspring under intra-specific competition. Being healthy is essential in this period. Energy expenditure has been used as a currency for explaining individual optimisation and fitness, but little attention has been paid to the structuring effects of health issues, though some studies suggest a major impact. E.g. parasitic infections in red grouse have been used to explain population cycles (Hudson et al. J. Anim. Ecol. 1992 61:477-486) and a trade-off between work load and the activation of the immune system and even survival has been shown (Hanssen. Proc.Roy.Soc.Biol.Sci.Series B 2004 271:925-930).
The Arctic environment has been proposed as a relatively save environment devoid of pathogens and parasites. Low densities of animals, isolation and cold weather conditions may hamper the occurrence of pathogens and parasites. Migration to Arctic breeding grounds would then be an adaptation to reduce the risk of infection (Piersma. Oikos 1997 80:623-631). Studying these issues on species which reproduce along a latitudinal gradient offers an opportunity to further explore this hypothesis and the special role of the Arctic. Infected migratory birds can be vectors of diseases and parasites with important economic consequences. Avian influenza is an example of a virus which is common in wild birds and for which migratory waterfowl has been described as a potential source for the outbreak in the Netherlands in 2003, which caused the killing of millions of chicken in an effort to stop the epidemic infection. The rapid spread of the West Nile Virus in North America is another example.

Pathogens and parasites are not always lethal and wild birds show regularly traces of past infections and co-existence. These traces can be correlated to population structuring processes via parameters of individual fitness like survival, reproduction and behaviour. Individual marked birds with a high re-sighting probability throughout the annual cycle are an optimal study object for relating health issues to non-lethal performance. Manipulation of health by curing infections with medicine (Righi & Gauthier Can.J.Zool. 2002 80:1077-1083) and testing the immuno-respons of individual animals (Deerenberg et al. Proc.Roy.Soc.Biol.Sci.Series B 1997 264:1021-1029) are experimental techniques to further examine the relation between health and fitness.

Objectives Study geographical variation in measures of health of arctic breeding birds and passed and present infections in relation to fitness. Manipulate health with medical treatment and study the effect on fitness. Model temporal changes in geographic variation.

Methodology (still under review) The following health parameters will be examined for each individual: 1. external parasite density (tics) 2. body condition (body mass corrected for size) 3. hematocrit (spinned capillary) 4. white blood cells (from blood smears and as buffy coat) 5. antibody titers (against sheep red blood cells and various diseases like Avian influenza) 6. intestinal parasites (traces and eggs in faecal samples, extracted with zincsulfate and analysed under a microscope). 7. imuno-respons to sheep-red blood cells (injection of sheep red blood cells during first catch and measuring anti-body formation at repeat catch after fixed interval). More parameters are under scrutiny or development.

Intestinal parasites (cestodes, nematodes and trematodes) can be removed by treating the animal orally with a Drontal solution. A group of animals treated against these parasites can be compared for behaviour and fitness with a control group treated with placebos (McCallum & Dobson 1995 TREE 10: 190-194). Hopefully more types of experimental treatment are available. Use of these tests needs further prioritisation based on the frequency of infection and the expected relation with behaviour and fitness.
Fitness measures like reproductive output and survival are based on sightings of ringed individuals.

Planning/ Time table - The project involves two years of field work (2007/2008) during the International Polar Year. Several prosals have been made already (see ) and the first workshop is planned 23-24 March 2006 in Groningen.

Funding - IPY is not a program with independent funding, but should lead to dedicated national funds for arctic research. Sofar, we have received funding in The Netherlands. We are on the final list in Norway and Canada is waiting for a decision.

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