People with Hearts of Birds will enter Jannah

"If you all depend on Allah with due reliance, He would certainly give you provision as He gives it to birds who go forth hungry in the morning and return with full belly at dusk".
[At-Tirmidhi]

Commentary: Trust in Allah does not mean that one should not give any importance to material resources. What it really means is that along with their due importance, one should have full trust in Allah. Without His Will, material resources are of no avail. But nevertheless it is necessary to have material resources because their procurement is also ordained by Him. Birds do not keep sitting in their nests for food but fly out in search of it.

Prophet (SAWS) said,
"A group of people (both men and women) whose hearts will be like the hearts of birds, will enter Jannah".
[Muslim]

It has been interpreted that such people are those who put their trust in Allah; another interpretation is that these people are tender-hearted.