begging-call is used by juveniles to beg for food from parents. Learnt behaviours An interesting example of culturally transmitted learning in birds was the phenomenon dating from the 1920s of blue tits teaching one another how to open traditional British milk bottles with foil tops, to get at the cream underneath Such behaviour has been suppressed recently by the gradual change of human dietary habits (low-fat or skimmed milk instead of full-fat), and the way of getting them (from a supermarket in plastic containers with hard plastic lids, instead of the milkman). In addition, the instinct to strip bark from trees in search of insects has developed into a tendency to peel building materials such as thatch, wallpaper, stucco and window putty. Predators and natural threats The small size of the Eurasian blue tit makes it vulnerable to prey by larger birds such as jays who catch the vulnerable fledglings when they leave the nest. The most important predator is probably the sparrowhawk, closely followed by the domestic cat. Nests may be robbed by mammals such as weasels and red squirrels, as well as introduced grey squirrels in the UK. The successful breeding of chicks is dependent on sufficient supply of green caterpillars as well as satisfactory weather. Breeding seasons may be affected badly if the weather is cold and wet between May and July, particularly if this coincides with the emergence of the caterpillars on which the nestlings are fed. Parasites Eurasian blue tits are known to be host to feather mites, and rarely lice and flat flies. In Europe, the only feather mite species known to live on the blue tit host is Proctophyllodes stylifer. However, this mite seems to be of no concern to the bird as, until now, it is only known to feed on dead feather tissue. P. stylifer lives all its developmental stages, i.e. egg, larva, protonymph, tritonymph and adult, within the plumage of the same host. The usual sites where P. stylifer is encountered are the remiges and the rectrices of the bird where they can be found tandemly positioned between the barbs of the rachis. Status and conservation The Eurasian blue tit is classified as a least concern species on the IUCN Red List (version 3.1), and as a Green Status species, since 1996, by the Royal Society for the Protection of Birds in the United Kingdom. Cultural significance The Eurasian blue