Nidalee's cougar form abilities don't give you tear stacks.

UNIQUE – MANA CHARGE: Grants a charge every 4 seconds, up to 3 charges. Each spell cast or mana expenditure consumes a charge and grants +4 mana, up to a maximum of 750 mana.

It has to be a spell, the spell doesn't have to cost mana. Nid's cougar abilities used to stack tear, but don't do it anymore, despite neither Nid nor Tear having been changed to that end.