WAR OF ATTRITION
1st JUNE 2020
“Big fleas have little fleas that live on their backs and bite ‘em,
Little fleas have lesser fleas and so ad infinitum”
(From “Siphonaptera” by Augustus de Morgan 1872)
No, this piece is not about fleas, but that little rhyme shows nicely that, in nature, all organisms depend upon others to make a living. Magpies get “bad press” for their way of making a living as it involves predatory habits, especially when it comes to the eggs and chicks of smaller birds. Although research has shown that this has no impact on songbird populations (Gooch et al 1991), nevertheless the bad press still sticks to them. But Magpies also have problems of their own, and they come in the form of Crows.
Gert Baeyens studied Magpie nests in the Netherlands (Baeyens 1980) and looked at the visits they got from other members of the family such as Jays, Jackdaws, Rooks and Crows, as well as other Magpies. Of these, the biggest interference in Magpie breeding came from Carrion Crows. These birds are about twice the body weight of Magpies and will steal nest material, eggs, chicks and even take over the whole nest. Although Magpies will occasionally drive them away, the bigger bird usually ends up winning. Magpies disturbed in this way had virtually zero chance of successful breeding when that happened (Baeyens 1980).
In the spring of 2020, Homo sapiens had a new enemy called the Covid-19 virus, which kept many people at home, reduced road traffic enormously, and brought air traffic to almost nil. These quiet skies meant that recording from my garden became a pleasant pastime rather than one spoiled by the rumble of planes at Geneva airport (even though it is 30km away). A pair of Magpies had taken up residence at the top of a tall spruce tree in a neighbour’s garden, but a pair of crows also took a liking to the tree and a war of attrition ensued which lasted for about 2-3 weeks. This enabled me to finally, spend the time to understand a little about the loud, but for me confusing, calls of Magpies. You can see more details here.
About 20-30 times each day the Crows would make a sortie on the Magpie nest and battle would commence, the Magpies watching for them lurking about, and the Crows waiting for their perfect moment to move in. The video below is an annotated sonogram of one such 2 minute encounter which I selected for the variety of sounds in the exchange.
The Magpies won this particular round, but eventually they gave up in the face of so much harassment and moved elsewhere. They are still around and I see them most days, but I do not see any signs of a replacement nest.
You can find more Magpie calls and a deeper explanation here.
