The video clip below shows the adult Pied Fantail (Rhipidura javanica) eats a faecal sac excreted from the chick in the nest. Now why did the adult do this?
Faecal sac is a gelatinous capsule containing the excreted droppings, or faeces of a nestling (Erritzoe et al., 2007). Immediately after feeding, the chick will turn its posterior towards the adult and a faecal sac will emerge from its vent (external opening of the cloaca). The adult will pick it up and dispose it some distance away LINK. If there is a running stream, the adult will drop it there. If a swimming pool is nearby the sac will end in the pool.
Faecal sac removal is a matter of nest hygiene. Furthermore, leaving the sac at the bottom of the nest will attract attention from potential predators.
During the first few days of a chick’s life, its digestive system lacks the necessary bacteria to complete digestion. The droppings are thus rich in partially digested food. Thus the adult will swallow the faecal sac to benefit from the nutrients they contain – see HERE.
17th July 2018
Erritzoe, J., K. Kampp, K. Winker & C. B. Frith, 2007. The ornithologist’s dictionary. Lynx Edicions, Barcelona. 290 pp.
This post is a cooperative effort between Birds, Insects N Creatures Of Asia and BESG to bring the study of birds and their behaviour through photography and videography to a wider audience.