(This column was first published in the January 10, 2000 Buffalo News.)
You were brought up more respectably than I was if you have not heard anyone referred to as a "birdbrain." That slang word has even made it into our recorded language. My American Heritage Dictionary, for example, defines birdbrain as "a person regarded as silly or stupid." Through my life, I was too often the referent to forget that word.
Indeed birds are creatures driven by instinct. Scientists refer to this as their being hard wired. Their stereotyped lives fit into narrowly defined patterns from which they rarely stray. They do sing, but for most species it is the same refrain -- often beautiful to be sure -- repeated over and over and over, ad nauseam.
Birds do learn, however. Among the famous Darwin's finches of the Galapagos Islands is one species that learned to pry out insects with a stick, a rare example of tool using by non-humans. On a more prosaic level, birds have also learned -- adapted at least -- to build nests in man-made shelters and to take meals from increasingly complicated feeders.
But my favorite example of bird learning was reported in the early 1950s by the English ornithologists James Fisher and R. A. Hinde in British Birds.*
In order to tell this story I provide some background for younger readers. Until those paper milk cartons that are used today were introduced shortly after World War II, milk was universally sold in glass bottles. And before milk delivery was curtailed and finally almost completely eliminated since then, those bottles of milk were delivered to home doorsteps or milkboxes by milkmen. When I was a youngster, those milkmen traveled in horse-drawn wagons, but by the 1950s (when I was a milkman myself) the horses had all been retired and trucks were used.
An aside: Older readers will recall how we learned that ice expands. The milk in bottles left out in sub-zero temperatures would freeze and push up through the bottle neck to form a white extension, the bottle cap still resting atop this column of milk ice.
Back to the story. Fisher and Hinde tell about British tits, close relatives and look-alikes to our chickadees, learning to open those glass milk bottles in order to drink the milk. They would prize the paper or tinfoil cap from the bottle by piercing it and prying it up. Having gained access to the milk (or more often the rich cream that rose to the top in those times before so much milk was homogenized) they would drink significant amounts. In a few cases they would steal so much milk that they would slip down the narrow neck and drown.
How did these birdbrains learn this technique? Fisher and Hinde are professional ornithologists so they very carefully hedge their conjectures with the usual "need for controlled studies," but the information they report supports a quite reasonable history.
The first record of this form of milk theft was from a Southampton village in 1921 and maps of later records indicate that the activity spread in geographic circles of increasing radii from there and from two other initiation sites near Manchester and Belfast.
This certainly suggests that individual (gifted?) birds found how to remove these caps, almost certainly through a kind of fortuitous trial-and-error. For example, they may have found a capless bottle or a bottle with its cap awry and started from there. Other local birds observed the activities of this avian research scientist and copied it, thus spreading the word through their communities.
The technique was even picked up by other species including two that are well known to American birders -- the house sparrow and starling.
Birdbrain indeed.-- Gerry Rising
* James Fisher and R. A. Hinde, "The Opening of Milk Bottles by Birds," British Birds 42 (1950): 347-357 and R. A. Hinde and James Fisher, "Further Observations on the Opening of Milk Bottles by Birds," British Birds 44 (1952
* James Fisher and R. A. Hinde, "The Opening of Milk Bottles by Birds," British Birds 42 (1950): 347-357 and R. A. Hinde and James Fisher, "Further Observations on the Opening of Milk Bottles by Birds," British Birds 44 (1952 ): 393-396.