Predators are a leading cause of breeding failure as well as adult mortality in most bird species, prompting the evolution of various antipredator behaviours. Among these, cryptic breeding birds often rely on strategies such as nest concealment and reduced activity to avoid detection. However, even some cryptic species have been observed to respond more actively to an approaching predator. One behaviour suggested to have an antipredatory function is defecating over the nest and eggs when departing. In this study, we investigate this behaviour in incubating female Eurasian woodcocks (Scolopax rusticola) using a large data set of 399 photographed nests sourced from various open-source internet platforms. Our analysis reveals that signs of defecation are obvious in 54% of nest photos. Moreover, in 67% of nests are visible freshly moulted feathers are visible around the nest, indicating possible application of fright moulting-a behaviour not previously documented in the context of the antipredator response during escape. We give both these behaviours a common context and suggest that they may help to aid the female's escape rather than to protect the nest, although their antipredatory nature, let alone their effectiveness, remains unclear. The presence of faeces and feathers may, in fact, increase the risk of nest predation by making the nest more conspicuous to predators. Our findings thus also emphasise the importance of minimising nest disturbance during research to preserve the integrity of the nest environment. We show that open-source platforms can provide valuable data for studies of breeding behaviour in wild birds.

Faculty of Environmental Sciences Czech University of Life Sciences Prague Czech Republic

Forestry and Game Management Research Institute Jíloviště Czech Republic

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