If you think life is stressful, imagine what it's like for a magpie. At this time of the year, you have chicks in the nest and whenever you come near, they start squawking for food. The magpies next door are stroppy. The local peewees and wattle birds bomb you, and even the wagtails will have a go. Then there are the ravens and possums who'd raid your nest if you're not careful. Down below are invaders you've never seen before in the form of cyclists and pedestrians who might need a reminder that you have a nest and they have no business in your territory.
Feeding yourself and the family is a full-time job that requires foraging for scraps. Just about anything insectivorous and worm-like will do, but one favourite are the scarab larvae that live under lawns and could damage whole fields if it weren't for the magpie. Watching a magpie, one can see they follow a systematic routine when foraging.
They walk slowly, scanning the ground, then stop and look closely with both eyes, remaining absolutely still. Then, at the last moment, they turn their head so that their left ear is close to the ground before straightening up, and executing a powerful jab into the ground. Having retrieved a scarab larva, they expertly remove the hard head and then bite off the mandibles before swallowing it or feeding it to an offspring.
To test the idea that magpies are using auditory cues while foraging, researchers recorded chewing sounds of larvae feeding underground. They played back these sounds through micro-speakers under controlled conditions, to see whether magpies would locate the source by the faint sound alone. Amazingly, they could.
It's a remarkable feat because scarab larvae are invisible on the surface, and are extremely quiet, with sound levels at only 30-38 dB. The only noise is their faint nibbling and cutting sounds of the grass roots.
Even more curious, perhaps, is that the magpies have been observed consistently using their left ear rather than their right when foraging for hidden food sources. This is one of a number of left-right biases that have been observed. When visually scanning the ground, for certain tasks and situations they favour their right eye, and while tracking moving prey or a potential predator such as a lace monitor, they favour their left eye.
Response by: Professor Gisela Kaplan, author of Australian Magpie (2019) CSIRO; and Bird Bonds (2019) , MacMillan
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