The concept is good and easy to understand. Bg looks great(if only it was repeating) and birds don't look out of place. The music choice is the best, without it the game would be plain boring, just make it quieter in menu. Some things to consider for you:
All sprites are in different quality, which makes some things blurred and some awfully out of place.
The text of health and speed doesn't have a shadow, and when on white background makes it invisible
Hitboxes of "attacking" birds are not matched with their sprites (probably because sprite has some blank space which counts as hitbox). That killed me not once
Most birds have white spaces in it (bro take sometime in photoshop to clear it), and shutterstock sometimes is seen on wings, just google "shuttestock remover", it's not hard
After around 2.5 minutes the background dissapears ( i understand that you thought that noone will play that long, but at least make it cycle itself)
And that's all I can say, not too bad, the music saves everything. Hope you to see more things from you soon!