Bird is regurgitating strange food to feed nestlings

This bird is regurgitating strange food to feed nestlings. Parent bird is feeding the chick with a fish or a big shrimp. It seems that this strange food has legs or something like that sticking out. What do you think it is?

This is a little bittern bird. It is a wading bird of heron family. It inhabits fresh marshes and wetlands with reed beds. It feeds on fishes, amphibians and insects which are caught within reedbeds or at their edges by the bird slowly stalking the prey.
Usually little bitterns make nests in the reeds as well.

This is a unique video documenting a nesting pair of little bitterns in Primorsky Krai (Far East of Russia). The closest documented breeding of little bitterns is 1500 km to the West of this area.

The video was filmed near Vladivostok, Russia by Amur-Ussuri Center for Avian Biodiversity.

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