All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is not an obligation to feed the free birds and the like. Rather, it is considered a recommended good deed for which a Muslim is rewarded. The Prophet said: “Never does a Muslim plant a plant or cultivate a land and out of that a bird or a man or an animal eats but he is rewarded for it as an act of charity.” [Al-Bukhari and Muslim]
The apparent meaning of the Hadeeth suggests that such a person is rewarded even if he did not intend to gain reward by doing that. Therefore, he gets the reward with greater reason when he actually intends to gain reward by it.
The story of the man whom Allaah forgave because he gave water to a thirsty dog is a good example in this regard. The Companions, may Allaah be pleased with them, asked the Prophet 'Is there a reward for us in serving the animals?' He replied: "Yes, there is a reward for serving any living animal." [Al-Bukhari and Muslim]
For more benefit, please refer to Fatwa 144991.
Allaah Knows best.