By Joe Smith of blog.nature.org
A subsequent experiment added yarrow to the nests of tree swallows, which don’t normally use medicinal plants. The result: the abundance of blood-sucking fleas was reduced in nests containing the plant.
Corsican blue tits also add plant material to their nests. They use lavender (Lavandula stoechas), mint (Mentha suaveolens) and an aster (Helichrysum italicum).
These birds add fresh plant fragments throughout the nesting period. When researchers experimentally removed these aromatic plants from their nests, the birds quickly replaced them.
Yarrow from Kohler’s medicinal plants 1887. Public domain.
For good reason it seems – chicks in nests with aromatic herbs had higher body and feather growth rates. The herbs also reduce the amount of and diversity of bacteria living on chicks.
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