What: “Run you pigeons! It's Robert Frost!” bronze trophy
When: During Year One (beginning of the game)
Where: Department of Death, rooftop
After being rescued by the LSA, you will have two things to do now: get Eva a set of teeth that can access the DoD computers, and get some pigeon eggs for Salvador. To help Salvador, you must have access to the roof, which I will not spoil on how to get there. Once you do get up there, you will see a huge flock of skeletal birds surrounding the eggs in question.
Return to the clown and ask him to twist up a balloon of Robert Frost and then return back to the rooftop. With the balloon out, look towards the birds and interact with them. Manny will say this line and the trophy will unlock soon thereafter. This trophy can be missed if you do not do this before leaving El Marrow.