Meta-tool use in New Caledonian crows

Here's an interesting PBS documentary on crows (I just remembered the interesting section in this video about meta-tool use when I read about the previous post talking about crows fashioning a hook spontaneously). It also features the University of Washington's Prof. John Marzluff in a few parts.

For the section concerning meta-tool use, skip to 14:20 in the video. It's super cool and documents New Caledonian crows being able to use tools to get other tools to access their reward, something that even primates have difficulty doing. In Tim's earlier linked pdf to tool use in crows, they mention that it is difficult to "distinguish between behaviour shaped by known or easily conceived experiences of reinforcement (i.e., trial-and-error learning) and behaviour which appears to result from an abstract process of inference". The quick meta-tool use trial in the video seems to point to the latter.