Inspired by the observations of Kees Swennen on the occurrence of dwarf eggsin a particular cohort of Eider ducks during his years of studies on Vlieland, I investigated theoccurrence of dwarf eggs in Herring Gulls and Lesser Black-backed Gulls on Texel based on aseries of fifteen years of observation (2006-2020). Dwarf eggs (<50 cc) were found to be seven times more common in Herring Gulls (0.57%, n=2831) than in Lesser Black-backed Gulls(0.08%, n=3724), without any obvious explanation. Almost every year, one or a few dwarf eggswere found in Herring Gulls, always in nests in which some eggs of normal size. Neither the agenor the breeding experience of the females played any role as far as could be ascertained, andinsofar the females were marked with colour rings and could be followed for several years, theywere not sterile. The dwarf eggs are seen as accidental and as temporary disruptions to theproper functioning of the sexual organs.
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