This page of the Far Cry 6 game guide contains a walkthrough of the "A Little Birdie Told Me" Treasure Hunt available in El Este.
Subregion: Sierra Perdida.
District: Promise Peaks.
The task is initiated by reading the note located right next to the grave.
Your task is to reach the chest and you must follow the pelican to get there. Start by feeding it, then drop down behind it from above. Having the Wingsuit during this mission is very convenient. You can find out how to obtain it on a separate page of our guide.
When you finally land, it's time to repeat the task. Feed the animal first, then hop on the nearby vehicle. It will make it easier for you to follow the pelican.
For the third time, feed the pelican and then follow it (this time by air).
The game will continue once you land on the shore. Feed the pelican, then hop on the water scooter. It allows you to easily catch up with the pelican and avoid losing mission progress.
When you finally arrive at your destination, once again feed the pelican. You will obtain the key this way. It will allow you to open the chest and thus complete the mission.