Unusually Long Incubation Including Interactions with the Mate by a Female Japanese Tit Parus cinereus minor in the Absence of Eggs

Breeding birds exhibit behaviours such as incubation and food provisioning, but proximate cues affecting the timing and duration of these behaviours remain poorly understood. In the Japanese Tit Parus cinereus minor, females incubate eggs and are provisioned by their mate. We report an unusual case of a female Japanese Tit incubating for at least 20 days without eggs, during which the female continuously interacted with its mate and was likely provisioned by him. We suggest that terminating incubation may require signals from chicks, and male provisioning may be triggered by female behaviours, such as incubation, begging displays or begging calls, rather than eggs. The development of a brood patch and nest building behaviours suggest elevated oestrogen levels in the female. Future research should explore proximate cues and hormonal regulation for these behaviours during breeding.