• ammonia;
  • emissions;
  • seabirds

[1] Ammonia emissions were measured from two entire seabird colonies with contrasting species assemblages, to ascertain the ammonia volatilisation potentials among seabird species in relation to their nesting behaviour. Emissions were calculated from downwind plume measurements of ammonia concentration using both inverse dispersion and tracer ratio methods. Measured colony emissions ranged 1–90 kg NH3 hour−1, and equated to 16 and 36% volatilization of excreted nitrogen for colonies dominated by ground/burrow nesting and bare rock nesting birds, respectively. The results were applied in a bioenergetics model with a global seabird database. Seabird colonies are found to represent the largest point sources of ammonia globally (up to ∼6 Gg NH3 colony−1 year−1). Moreover the largest emissions occur mainly in remote environments with otherwise low NH3 emissions. These ammonia “hot spots” explain significant perturbations of the nitrogen cycle in these regions and add ∼20% to oceanic ammonia emissions south of latitude 45°S.