Disguises

so ive been trying to disguise a chicken as melon seeds and i cant seem to make it work, even the manual page on droped items doesnt seem to work, anyone know how to do it? all help is appreciated.

Heres the Code i put

Ant:
Type: CHICKEN
Display: 'Ants'
Health: 1
Disguise:
Type: ITEM
Item: MELON_SEEDS
ItemData: 0


I tried out different ways but since this is what the manual page said ill put it like this.