Why do domestic cats 'chatter' when looking at a bird through a closed window?

The infographic provides my answer to the question in the title. I don't think that you will see a better answer to this much asked question. If you have some thoughts please comment. Thanks.

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P.S. please forgive the occasional typo. These articles are written at breakneck speed using Dragon Dictate. I have to prepare them in around 20 mins. Also, sources for news articles are carefully selected but the news is often not independently verified. And, I rely on scientific studies but they are not 100% reliable. Finally, (!) I often express an OPINION on the news. Please share yours in a comment.