Thanks so much for playing! You are 100% correct, currently the idea is that your bird will only last so long and by upgrading you eventually can eat more to have your bird survive longer. So time is really what you are competing against. We spent so long getting the simulation together we didn't have much time to play test and find out how others would see the gameplay loop. So it's a little rocky in its current state. We are definitely considering how to alter this after the jam and already have some ideas!
For the end of the game you just have to consume all the enemy boids so when you upgrade food to that point you are essentially in the last stretch of the game.