what the heck do these ducks do
they drop out when someone gets killed
If you purchase (or trade for, currently 1.5-2 Keys) a Duck Journal and equip it in the Action slot, you can collect the ducks to go on a "Duckstreak" (You can also use your Action key to use your Duck Journal as a quacking noisemaker)
These streaks are similar to Killstreaks, except they feature a duck icon in the killfeed instead of a chevron, and the on-screen notifications have duck-themed ranks
Different actions with the dropped ducks (collecting them from enemies, "denying" enemies by picking up ducks from your fallen teammates, etc.) also provide experience to your Duck Journal that level it up similar to a Strange Weapon, again with duck-themed ranks, and increase the amount of ducks that drop when you kill someone
There's apparently also a leaderboard for the people who have collected the most ducks but that pretty much doesn't matter because I guarantee the top 100+ people have been playing nonstop since EOTL began with maxed out Duck Journals and pockets full of Duck Tokens
Related, I just got a notification that I'd reached Duck Level 1 but I don't have a Duck Journal, what's up with that