Ecological Immunology of Avian Hosts

Ecological immunology of avian hosts explores how birds allocate limited resources to immune defence within the context of their life history, environment and interactions with parasites and pathogens. This field emphasises the trade-offs between innate and acquired responses, the costs of maintaining immunocompetence and the influence of factors such as nutrition, stress hormones and environmental variability on host defence. Research has revealed that baseline and induced levels of hormones—especially glucocorticoids like corticosterone—modulate immune function, shifting the balance between resistance and tolerance to infection. Avian hosts encounter a diversity of blood parasites, notably haemosporidian genera (Plasmodium, Haemoproteus and Leucocytozoon), which undergo both erythrocytic and exo-erythrocytic development. The outcome of infection is shaped by host species, age, habitat and behavioural traits such as flocking or nesting strategy. In a changing world, factors such as urbanisation, climate warming and pollutant exposure can alter vector distributions, host stress physiology and immune parameters, producing complex patterns of disease prevalence and intensity. Insights from ecological immunology inform conservation strategies by identifying physiological biomarkers of health, predicting disease emergence in novel environments and revealing the capacity of avian populations to adapt immunologically to anthropogenic change.

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Ecological Immunology of Avian Hosts publication trend

The graph below shows the total number of articles in ecological immunology of avian hosts across all publications each year (not limited to Nature Index journals).

Technical terms

Innate immunity: The non-specific, immediate defence mechanisms (e.g. barriers, phagocytic cells and inflammatory mediators) that provide first-line protection against pathogens.

Acquired immunity: The antigen-specific immune response mediated by lymphocytes and characterised by immunological memory, offering enhanced defence upon re-exposure to the same pathogen.

Haemosporidian parasites: A group of protozoan blood pathogens (including Plasmodium, Haemoproteus and Leucocytozoon) that infect birds, undergoing both blood-stage and tissue-stage development.

Glucocorticoid: A class of steroid hormones (such as corticosterone) produced by the adrenal glands that regulate energy metabolism, modulate inflammation and influence immune function in response to environmental challenges.

Exo-erythrocytic development: The phase of haemosporidian life cycle in which parasites multiply within host tissues outside red blood cells, often causing significant organ pathology.

References

1. Urbanization correlates with the prevalence and richness of blood parasites in Eurasian Blackbirds (Turdus merula). The Science of The Total Environment (2024).
2. Meta-analysis reveals glucocorticoid levels reflect variation in metabolic rate, not ‘stress’. eLife (2023).
3. Exo-erythrocytic development of avian malaria and related haemosporidian parasites. Malaria Journal (2017).