An experiment with wild crows & a box

Crows, (Carrion crow - Corvus corone) are known to be clever. I decided to make a small experiment with a box closed with 4 clasps, that can be open by manipulating at least 3 clasps. Among the many crows in this colony in Paris, only 3 or 4 did approached the box, revealing how important is the hierarchy. However, I did not recognize the gender of the birds, it could be either females or males... Crows do recognize each others among hundreds of individuals. 065, a marked crow, did the opening job by opening the first two clasps. In the end, it did not benefited any reward. It seems that a middle status crow have contributed unwillingly for top ranking ones. The opening of the box, after three clasps were released, happened in less than 10 minutes.