Individual consistency of hissing displays across night and day in a free-living female songbird.

Birds have evolved a variety of antipredator strategies, which have been extensively studied during day-time. Yet, how diurnal birds directly respond to nocturnal predation threats remains largely elusive, despite that predation risk can be high during both night- and day-time. One form of antipredator behaviour found in several tit species when confronted with a predator at the nest is the hissing display. As for many forms of antipredator behaviour, studies on hissing displays have so far focussed on the day-time. Here, we exposed cavity-nesting free-living female great tits (Parus major) to simulated predator intrusions inside their nest box during both night- and day-time. We showed that 28 % of females uttered at least one hissing call during night-time, while the occurrence of hissing calls was higher during day-time (84 %). Hissing females at night, compared to non-hissing females, produced more hissing calls during day-time, providing evidence for individual cross-context consistency. Night-time hissing behaviour did not predict lay date, clutch size, breeding or nest success, indicating the absence of consequences in terms of current reproduction. Together, we reveal the hitherto undescribed occurrence of hissing displays at night in a cavity-nesting bird, while simultaneously strengthening the evidence for the existence of hissing behavioural types.