SCOTT SIMON, HOST:
One human's trash just might be an avian's armoire. Urban birds have long used a wide assortment of building materials to build their nests - galvanized nails, barbed wire, even sheet music by BJ Leiderman, who writes our theme music. Now a team from the Netherlands has documented a number of birds' nests around Europe that are built from anti-bird spikes. These are strips of metal spikes that people attach to the eaves of buildings to try and deter birds from roosting there. Auke-Florian Hiemstra, a biologist at the Naturalis Biodiversity Center in Leiden, was the lead author of the paper and joins us now. Mr. Hiemstra, thanks so much for being with us.
AUKE-FLORIAN HIEMSTRA: Thanks so much.
SIMON: Can you describe a few of these nests for us?
HIEMSTRA: The very first nest I saw was a nest from Antwerp, in Belgium. And we also describe it in the paper as the biggest nest we found, a nest that included more than 1,500 nasty, metal, anti-bird spikes.
SIMON: (Laughter).
HIEMSTRA: Fifteen hundred - so that's like a bunker for birds.
SIMON: How do the birds wrestle them out of the material?
HIEMSTRA: Well, that's interesting. This nest was made in the courtyard of a hospital, and we also went to the roof of the hospital. And there were a lot of bird spikes. But all the bird spikes closest to the nest, they were gone, and just a trail of glue was present. But, yeah, I think the magpie ripped them off the roof and used them in its own nest. And actually, just making a nest out of anti-bird spikes is already hilarious. But they even use them in a very smart way as magpies do not only have a bowl...
SIMON: Yeah.
HIEMSTRA: ...A nest bowl, but also have a roof over their nest. And for this roof, normally, they search for thorny branches to actually prevent predation from the nest, so to ward off predators. However, in cities, there are not a lot of thorny branches, but there are a lot of anti-bird spikes.
SIMON: Yeah.
HIEMSTRA: And this is, I think, crazy. They use the bird spikes in the same way as they were intended to be used, namely to ward off other birds.
SIMON: Oh, that's hilarious.
HIEMSTRA: And I think that's just perfect.
SIMON: My gosh. Now, any birds more likely than others to use these spikes?
HIEMSTRA: Yeah. So a few species in particular use these spikes. We have examples of crows using them and examples of magpies using them. And so this is within the family of the corvids, and those are very smart birds, birds which are very intelligent, which are also using tools. They can do a lot of problem-solving. And so they also solved the problem of having no spikes in the city centers.
SIMON: Don't they have to worry about getting hurt using these - what I'll refer to as hazardous materials?
HIEMSTRA: Yeah. So the whole outside of the nest is covered with these bird spikes. But within the nest, it's this very safe place made with soft material. So the young ones are safe. But I think the - well, the parents may struggle a little bit to handle the material, but they managed to find a way...
SIMON: Wow.
HIEMSTRA: ...Which really reflects how animals now are adapting to our urban city life.
SIMON: Mr. Hiemstra, I'm moved to say, good for them.
HIEMSTRA: Yeah. Yeah. I think it's magnificent to see these rebellious birds actually fighting back. And actually, when you walk through a city, suddenly, you see them everywhere. And actually, like, it's a little bit sad, I think...
SIMON: Yeah.
HIEMSTRA: ...That we are so actively trying to fight our urban biodiversity while we also could, like, embrace those beautiful animals.
SIMON: Well, I'm impressed by your work, to be sure, but mostly the birds. Thank you.
HIEMSTRA: Thanks so much.
SIMON: Auke-Florian Hiemstra is a biologist in Leiden, the Netherlands. Thanks so much.
HIEMSTRA: Thanks so much for having me.
(SOUNDBITE OF SONG, "BIRD ON THE WIRE")
LEONARD COHEN: (Singing) Like a bird on the wire, like a drunk in a midnight choir... Transcript provided by NPR, Copyright NPR.
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