Very often, in a café, there will be a jug of mint infused water sitting in a corner, offered as a complimentary accompaniment to the coffee. A fragrant way of ‘refreshing our palate’. Mint is one of many aromatic plants that we use to scent our rooms or freshen our breath. But are we the only species that uses mint and similar aromatics such as lavender in this way? Do other animals appreciate the aroma that a freshly plucked mint leaf can provide?
A quick use of duckduckgo (or google if you’d prefer), revealed a surprising answer (or at least further questions) to this odd behaviour. It would appear that blue tits have been observed to pick mint, lavender and curry plant leaves and use them to line their nest. Moreover, individual blue tits have a preference for different plants. Some females (it appears to be the female that collects the leaves) prefer mint, some lavender, and presumably some prefer curry. There is even a video from “Springwatch” that filmed this behaviour in a blue tit nest a few years ago (link is here). Similar behaviour has been observed in some other bird species such as the Starling (Sturnus vulgaris) but not in other, related bird species such as coal tits or great tits. So what could be driving this behaviour, is it, as the BBC said in its headline “aromatherapy”?
According to research, in fragranced nests, the number of bacteria/pathogens on the chicks was significantly reduced compared with non-scented nests. The chicks also seemed healthier, not only did they have a higher red blood cell count, they grew faster. What remains unclear is the reason that this should be so. Is it that the mint is anti-bacterial? Or is it, as suggested in the programme Springwatch, that the smell can perhaps relax the immune system of the birds allowing them to “put more effort into their growth”. Moreover, how did the birds first know how to pick these plants? How did this behaviour spread?