The anthropogenic influence on wildlife hardly knows any boundary. We cause habitat loss and climate change, deplete natural resources and emit pollutants. In addition, we create ideal environments for the emergence of novel pathogens, such as a strain of highly pathogenic avian influenza virus that originated in poultry farming in the 1990s: H5N1. Seabirds are among the birds most affected by these changes and during the breeding seasons of 2022 and 2023 were introduced to unprecedented H5N1 outbreaks at their breeding sites. The long-term study population of common terns at the Banter See suffered immense losses of breeding adults, as well as their chicks, causing a population crash (see figure). Thanks to the long-term nature of our study, including access to archived blood and plasma samples, we are in the perfect position to (i) investigate which factors caused birds at this colony to die of avian influenza (e.g. sex, age, phenology, genetic variation at immunity genes, levels of mercury pollution), as well as (ii) to study the development and maintenance of antibodies against avian influenza.

To compare antibody development across populations and species, we have also started sampling common terns, as well as gull-billed terns making up the last Central-European breeding population, at Neufelderkoog.