Complex sentence: This complex behaviour, solved by six out of seven birds on the first attempt, involved realising that a tool could be used on non-food objects, and the suppression of the urge to go directly for the food, had previously only been known in primates.
Split into simpler sentences: This complex behaviour involved realising that a tool could be used on non-food objects, and suppressing the urge to go directly for the food. It was solved by six of seven birds on the first attempt, and had previously only been known in primates.