Thanks to Apple, many of us have decorated our homes with shiny white plastic items. It turns out that one type of bird does exactly the same thing.
Research in Spain has shown that the black kite that has the biggest collection of shiny white plastic pieces is likely to have the most chicks. (That can’t necessarily be said of we humans.)
A report published in the latest edition of Science magazine details how the plastic is displayed in nests as a status symbol: not as a sign of wealth (given the lack of banking facilities in the avian community), but rather a sign that the kite living there will aggressively defend the nest if attacked.
Staff at the Donana National Park investigated the issue after noticing that many nests had been filled with white materials, usually strips of plastic bags, but occasionally cloth or even paper. As well as taking note of which birds had which decoration, they also tried replacing or removing the rubbish to see if it made any difference.
The main conclusion was that the birds most likely to have the material were middle aged (in the sense of being between childhood and old age, rather than the “inappropriate ponytail and motorbike” sense), in the best physical condition, and most likely to take control of any food laid out by researchers. It also appeared that birds with large displays were more likely to rear multiple chicks in the same breeding season.
At one point the researchers tried adding plastic to the nests of lower-status birds, only to find that they almost immediately began removing it. This suggested the birds did not want to risk appearing to challenge the status of their stronger rivals. Those that weren’t quick enough to remove the plastic soon came under attack, apparently from other birds wanting to test the accuracy of the apparent status claim.
In another test, researchers put out shreds of bags that were white, transparent or green. In 29 out of 33 cases, birds only picked up the white shreds. That appears to not be a style choice, but rather a simple matter of the white being more visible.
(Picture credit: Spanish National Research Council )