When passive nest defence is active: support of the leave early and avoid detection hypothesis in a plover

Leaving the nest early to avoid detection by an approaching predator is an often‐cited form of nest defence among ground‐nesting birds, yet has rarely been quantitatively demonstrated. During the breeding season, we recorded Flight‐initiation Distances (FIDs) of incubating, off‐duty and non‐breeding Hooded Plovers Thinornis cucuallatus cucuallatus in Victoria, Australia. Hooded Plovers exhibited longer FIDs when incubating compared with when off‐duty or non‐breeding birds (the latter two categories had similar FIDs). Our study supports the Leave Early to Avoid Detection (LEAD) hypothesis, and demonstrates that so‐called ‘passive’ defence is in fact an active decision by the incubator to leave nests at distances which exceed those at which birds without nests or off‐duty commence escape.