Thursday, November 8, 2018

Chewing over corvid cleverness

Clever birds, corvids (crows and ravens). Toolmaking. Zip opening. Number counting. Canny Cane Toad chewing. Egg munching. Golf ball eating . . . Well, not so clever with the golf balls. And maybe some vaunted skills are more lab products than typical wild behaviour. Above, Australian Raven tearing at eye and shoulder, near poison gland, of toad - probably dead when found - today at Townsville Common Conservation Park. Terrible image, but taken from about 50 metres away.

Bird, without any sign of distaste then turned toad over and drove beak several times into underside trying to tear into flesh. Unfortunately it then flew off with toad so outcome unknown. But it seems clear raven never got the memo about avoiding toad toxins. And nor had its immature offspring, watching proceedings from beside parent. One case proves little, but I've argued previously that any sensible bird would seek to eat toads or frogs from the underside, because of the soft underbelly. No genius required.

Which brings us to golf balls. Stolen by hundreds every year from the 27 golf holes the Town Common almost encircles. Stolen and abandoned after failing to crack open like eggs. Year after year corvids steal hundreds of golf balls. Not an egg among them. How clever are they really? Better to be lucky than clever. Bumble along and stumble upon Bush Stone-curlew and eggs (above).

Curlew chases Australian Raven trio off. But they return. Two pick up eggs and fly off. What usually happens, I've since been told by witnesses to corvids raiding henhouses, birds fly off with egg, land, poke hole in top of egg, and eat contents without spilling a drop. I couldn't find any trace of eggshell along 40-metre flight path of adult raven carrying one of the curlew eggs. Bird (above) landed, egg was gone. Swallowed into thin air, or perhaps simply swallowed. Be a clever trick. But, then, they're clever birds. aren't they?

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