Photo by Paul Gavinger at https://www.flickr.com/photos/highlyecumenical/52796500456
Dear Readers, you may have noticed how much of our discarded ‘stuff’ seems to end up in birds’ nests and squirrel dreys. Scientists have been intrigued about what is selected and why for some time now – for example, magpies and crows have been spotted ripping the anti-pigeon spikes from buildings and incorporating them as a kind of spiky armour in amongst the twigs and leaves. However, scientists found birds using many other kinds of human-made objects in their nests, and speculated that corvids, notorious egg thieves, might be neophobic – afraid of new things – and that this might give the parent birds more time to defend their nests from the marauders.
Large feathers are also often found in nests, and one theory was that this looked as if a bird had been killed at the nest site, deterring nest predators from approaching.
Scientists Magne Husby and Tore Slagsvold, both from universities in Norway, constructed three kinds of artificial nests. One just contained quail eggs, one had eggs plus a shiny spoon, and one had the eggs plus large feathers. They then trialled the nests in a forest to measure the responses of magpies, and at a landfill site to measure what ravens did.
Magpies waited 96 hours before taking eggs from an ‘ordinary’ nest, 149 hours before raiding the nest with a shiny spoon, and 152 hours before checking out the nest with feathers. Ravens were much less hesitant, but still took 28, 34 and 43 hours respectively.
There is a substantial difference in time of predation between undecorated and decorated nests, and it intrigues me that birds are adapting to our ‘rubbish’ in this way. However, I do wonder – corvids are very fond of shiny objects themselves, so I’m surprised that the shiny spoon wasn’t more of a draw than anything else. As with everything else in nature, we may underestimate the effects of individual personality and choice, both in the parent birds and the egg thieves. This isn’t the end of the story, I’m sure.
You can read the Royal Society paper here.
I am just having a Monday morning catch up and hope you don’t mind a combined comment.
Many years ago I remember watching a blackbird persistently trying to feed its fledgling a small red rag and the youngster equally persistently refusing to have anything to do with it. It was dry weather and worms would have been hard to come by so we provided a few small bits of cheese as a more nutritious offering but the adult showed no interest in them
Thanks for all the cuckoos, I had no idea they existed and the different calls were fascinating but still recognizably cuckoos.
Fascinating!