Pigeon Post (Completely Reworked): A team-based secret signaling game [new rules critique please]

I like the game a lot, but I'm unfortunately not in a position to playtest at the moment. I like the realtime aspect too, but I wonder how you resolve it when people drop their cards for an exchange and two or more players grab for the same card simultaneously.

"Home bound carriers work like wildcards. They can be combined with any pair of identical bird species bound for the same destination."
I found this rule a bit confusing. I'm assuming you mean that a wildcard dove can be added to any dove flock, but that is not what you're saying. I'd use the following phrase:
"Home bound carriers work like wildcards. They can be combined with a pair of same species as the carrier bound for the same destination."

I'll have to mull over this new version before I can give detailed feedback, but my first thought is that I liked the original better.
The art was better in my personal opinion and also having destinations instead of numbers fits better theme-wise.

Perhaps you can lower the amount of things people have to remember by not requiring people to call the destination and allowing that for an expert game as a variant.

Also, 5 minutes seems a bit short to think of good signals for multiple things. I'd give it 10-15 max (based on the old rules). That allows the teams to make up backup signals if one or more of them are discovered.