Not cockatoos but I have had my hiking backpack opened by black currawongs in Tasmania: https://en.wikipedia.org/wiki/Black_currawong#Feeding https://en.wikipe

Not cockatoos but I have had my hiking backpack opened by black currawongs in Tasmania: https://en.wikipedia.org/wiki/Black_currawong#Feeding https://en.wikipedia.org/wiki/Black_currawong#Feeding My hiking buddy and I dropped our packs to climb Mount Ossa off the side of the Overland Track. We had been warned that the currawongs would try to get into our packs. So we zipped everything up tight, pulled the rain covers on and placed them face down (ie strap side to the sky). When we got back from we found the birds had pulled off my pack cover and managed to open the zip for the pocket on the top of my pack and pull out a bunch of stuff. The pack cover fit quite tight, so I was surprised the birds had the strength to pull it off. The zip needs to be pulled a just the right angle to move freely, so they must have known which way to pull the tag and been persistent at trying different angles until it opened. A quick search shows I'm not the only victim, the link below includes numerous matching stories with some photos of the aftermath: https://bushwalk.com/forum/viewtopic.php?f=37&t=23012 https://bushwalk.com/forum/viewtopic.php?f=37&t=23012