They're nothing to do with Magpies or Larks. Pie applies the old English usage of black and white. The lark part perhaps sprang from the birds' liking for muddy open spaces.
Magpie-larks turn out to be most closely related to monarch flycatchers - some of which are black and white - but otherwise show almost nothing in common with them.
Caught male bird above on thorny weed by a pond - a rare pose for a bird happiest on the ground and most definitely not chasing about in aerial pursuit of flying insects.
Picture is another plug for image stabilisers. Taken handheld with Panasonic FZ30+1.7x tele lens (700mm=) from rough-idling 4WD 'mobile hide'.