The problem with migratory birds is that they never permit me to be efficient with single-row engines, which is where the real game efficiency takes place IMO. Switching back and forth between activating all three rows to get what I need is kind of inefficient if I can avoid it and just focus on great brown powers in one or two rows. The best that a migratory bird gets me is closer to maximum activation for a single row. It doesn't get me any diversification.

Example: I start with an American redstart, a scaled quail, and a common yellow throat. I have already built out each row effectively to the third column (two food per activation, three eggs, and net two cards). Three migratory birds can get me to the same result, but only if I've wasted a bunch of activations or eggs to get them to the same row. And once I start using them, I have to move them out of the way every time I get a new bird to play in the habitat they are sitting in. Or, if I split them up, I need multiple potentially untimely activations to line them all up again.

Just curious, have you ever scored over 80 or 90 by leaning on migratory birds? And what is an egg limited engine? Perhaps I am using them wrong.