The case of subcutaneous emphysema in a Eurasian reed warbler nestling

Abstract

AbstractReports of physical abnormalities in wild bird populations are rare and often anecdotal, whereas reliable estimates of their frequency are important to understand the strength of selection against them. In 2005–2022, we studied various aspects of breeding biology of Eurasian reed warblers and monitored a total of 1194 nests. In July 2022, we observed a deformed nestling of this species in a brood of three young. The nestling displayed a soft distended lump around the cervical area. After further inspection, we concluded that the nestling suffered from subcutaneous emphysema, which resulted in its death on the following day. The nestling body was collected and examined for the presence of injuries, parasitic nematodes and bacteria. We discuss possible factors that might have caused the nestling’s emphysema and conclude that Clostridium bacteria found in the nestling tissues were the most likely cause of its symptoms and death. This was the only case of subcutaneous emphysema recorded in our population among 1995 nestlings of the same age (8th day after hatching), making up 0.05% of all.

Keywords

• Subcutaneous emphysema
• Eurasian reed warbler
• Acrocephalus scirpaceus physical abnormalities
• nestling