Maybe you're familiar with the arsehole behaviour of cowbirds. Known as "brood parasites", cowbirds lay eggs in another bird's nest and trick the host bird into raising cowbird offspring at the expense of her own. Like I said, arseholes. But birds can learn to recognise imposter eggs. That's where 3D printing comes in.
To study how host birds, such as the American robin, reject brood parasite eggs, scientists have relied on making fake eggs. That could be eggs taken from another bird (problematic, also limited sizes and shapes) or eggs hand made from plaster or wood (not hollow and not realistic). A possible solution then? 3D printing.
In a paper published in PeerJ, scientists described how to 3D-print hollow eggs of plastic filled with water. The eggs can then painted to give them the right colour: blue for robin's eggs, white for cowbird's. 3D printing makes it easier to create fake eggs on demand and also continuously tinker with size and shape.
Initial tests show the 3D-printed eggs stack up pretty well against other out-dated alternatives. When the fake eggs were painted blue as a test, robins accepted all the eggs. When they were painted white, they accepted only 21 per cent of them — in line with past experiments with fake plaster eggs.
But more refined 3D-printed egg could even be better. Host birds sometimes try to pierce eggs they recognise as imposters, which is obviously not possible when the fake is a solid plaster or wood egg. That could actually be skewing the results. Hollow eggs, though, could also be made to be pierce-able and all the more realistic.
Picture: Igic et al/ Peer J