47 : Milk bottle top

1921

The rapidity with which Blue and Great Tits discovered how to peck through the aluminium foil caps of traditional glass milk bottles to access the cream demonstrated how quickly knowledge of a food source can spread among wild birds; the introduction of waxed cardboard cartons showed how quickly it can be lost.

Birds are not just the ever-elusive objects of their observers’ desires to collect ticks on a list, or representations of their beholders’ need to have specialist or secret knowledge – many draw immediate attention to themselves or exploit humans’ own environments and products.

This is nature’s way, of course, but it is also perhaps why most people, whether habitual birdwatchers or just appreciators of nature in the broadest sense, feel some kind of connection to the presence and activities of birds. They share human space in ways which are described in biology as parasitic (where one party profits to the detriment of the other), symbiotic (a mutually beneficial relationship) or commensal (where one party benefits without detriment to the other).

Birds inhabit and exploit farms, gardens and homes all around the world. There are many campaigns to combat the decline of farmland birds brought about by intensive agriculture, though their remembered numbers are very much artificial in themselves, products of the adaptation of scrub and woodland-edge species to the patchwork of habitats created by the development of arable land in the first place. The even bigger picture is that farmland is also mitigation for the wholesale destruction of woodlands and their ‘edge’ habitats, as Britain and Europe was rapidly deforested over the last 2,000 years or so.

A now-rare and prosaic example of birds’ lives interweaving with humans is the phenomenon of cream stealing. The ‘milk snatchers’ in this case were not acolytes of Margaret Thatcher but some of our most common garden birds: Blue and Great Tits, and Robin. Birds cannot digest lactose-rich cows’ milk but, given the opportunity, will enjoy the lactose-free cream. This habit was perhaps originally developed in the late 19th century when they raided domestic dairy deliveries, but first properly documented in 1921 when birds described as tits were seen to prise open the wax-board tops of bottles on doorsteps in Swaythling, near Southampton.

The pre-war provision of aluminium caps on milk bottles – with colour codes of gold (cream-rich Guernsey and Jersey milk), silver (whole milk), red (homogenised), red and silver (semi-skimmed) and so forth – provided only temporary respite from the depredations of otherwise insectivorous birds; with their sharp beaks they were easily able to peck through to the cream below, the bottle lip acting as a handy perch. Robins developed the skill locally, but the habit spread through the national populations of both tit species.

With changes in milk consumption preferences, the decline of doorstep milk deliveries and the widely adopted switch in milk packaging to plastic bottles and Tetrapaks, the phenomenon has virtually died out. Today’s garden birds rely far more on bird feeders than the almost non-existent prospect of free doorstep cream. However, the rise and fall of the cream thieves emphasises the malleability of our most familiar avian neighbours as they perform the dance of adaptation around our own changing habits.