Nicolás found a nice flock of Hooded Siskins and their behaviour called his eye. "I was walking along the vegetation when I found between the Canal Sudeste and the path a place which had recently been cleared. As I walked in a group of siskins flew from the ground to nearby bushes. I stayed still and saw a lot of them return in a second (I estimated 50 individuals, males and females). I had never seen that many!
"All of them" had the same behaviour: they landed on the ground from the bushes and looked for something, alone or in small groups. They picked small sticks 2,5 cm long and a cigarette-like wide. As they got it, they flew back to the bushes. I could not see what they did with the sitcks. They seemed to be taking them for some reason, but I discarded that they were using them to build nests. Neither could I see if they obtained something from it. It seemed to me they did not, since they only picked it and flew, they did not even peck at it."
The time this occurred, April is not breeding season. They do not breed in colonies and sticks is not the material for nests. In my opinion they were eating. The ground was covered with seeds and insects as a result of weeding. This was the attraction why they did not leave the place and returned. I imagine that to obtain the insect from the stick as they are on the branch they use the same technique as when taking seeds out of a fruit. They use their foot to hold the stick firmly against the branch while they use their bill.