Dear Readers, my British Trust for Ornithology newsletter had a fascinating question this month. It was from a woman who had noticed that the juvenile starlings in her garden were pecking at the heads of flowers and sometimes tearing them off without eating them. “Are they looking for bugs, or are they just being naughty?” asked the writer.

Well, I’m not sure about the concept of animals being ‘naughty’, though I’ve had pets that definitely knew when they were pushing the boundaries. The answer given was the one that I would have given – juvenile animals often imitate adults without exactly knowing why, and they learn by trial and error. So, I see all sorts of baby animals pecking randomly at first, and then gradually learning what tastes good. Within a few days or weeks, they are able to find their own food.

However, the article then goes on to explain something that I wouldn’t have guessed. Starlings often use green plants in their nests, choosing in particular wild carrot (Daucus carota) and fleabane (Erigeron philadelphicus). The data was taken from an  American study (European starlings were introduced to North America in the 1870s) so I wouldn’t expect them to be using this particular species of fleabane, which is a New World native, here in the UK (unless they’re taking it from gardens). There’s plenty of wild carrot though!

Wild Carrot (Daucus carota)

Philadelphia Fleabane (Erigeron philadelphicus) Photo By D. Gordon E. Robertson – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10314173

What the researchers found was that the wild carrot and fleabane greatly reduced the number of blood-sucking mites found in the nests, compared to nests which did not contain these plants. The chicks from ‘green’ nests had higher levels of haemoglobin than the other chicks, indicating that they were less prone to the anaemia that occurs in chicks from nests with high levels of mites.

Were the starlings just choosing plants randomly, though? It appears not. The starlings were also offered garlic mustard (Alliaria officinalis) but they weren’t interested – in the laboratory, it was found that this plant had no effect on the numbers of mites.

However, not all research has shown that ‘green nests’ in general show a reduced burden of ectoparasites. So what else is going on?

The plot thickens with a UK study which showed that nests containing green plants resulted in better parenting behaviours – the eggs were incubated for longer, the parents spent more time at the nest, and foraging began earlier in the day. Furthermore, the eggs developed more quickly and the chicks gained bodyweight more successfully in ‘green’ nests than in those that contained no plants.

What’s going on? There seem to be a variety of things. Female starlings preferred males who included green plants in their nest-building displays, and this could be a way that the males demonstrate their ‘quality’ as mates. But one tantalising hypothesis is that the plants release volatile chemicals that sedate the incubating birds, and encourage them to stay put for longer. The scientists in the study point out that the starlings in the green nests spend most time on the nest at the beginning of the incubation period, which coincides with strongest release of the chemicals (as the plants dry out they release less and less of the sedating compounds). The beginning of the incubation period is also the most critical for the development of the eggs.

‘Green’ nest (Photo fromhttps://www.sialis.org/nestsstarling/)

There has been a lot of research into the ways that animals interact with plants, both to medicate themselves and to deter parasites. I’m seeing lots of photos lately showing jays and other birds ‘anting’ – placing themselves on top of ants nests, or even using individual ants to remove parasites as the insects spray formic acid. I hadn’t heard of the ‘green nest’ phenomenon before, though, and I’m completely fascinated. There are certainly advantages to sitting around with your leg up, one of them being that i’m actually reading some of the things that pop into my Inbox. Thank you, British Trust for Ornithology!