Long before storks began flying across birth announcements with babies dangling from their beaks, Europeans were already associating the birds with fertility, family and good fortune.

White storks made unusually convincing symbols. They returned from their annual migrations in spring, built enormous nests on rooftops and chimneys, and were attentive parents. A stork nesting on a house was considered a good omen in parts of Europe, and over time the birds became increasingly entwined with stories about marriage, pregnancy and new life.

In parts of northern Europe, old folklore associated water with fertility and new life, and some traditions imagined unborn children or their souls waiting in wells, ponds or springs. Storks, which commonly fed in wetlands and were already associated with family and fertility, became linked to these stories. In German folklore, people could even appeal to a stork to bring a baby, helping set the stage for the familiar story of storks delivering newborns.

Then Hans Christian Andersen helped the story travel. His 1840 tale The Storks describes storks collecting babies from a pond and delivering them to families. Andersen did not invent the association, but the popularity of his stories helped carry it well beyond the regions where the folklore had developed.

By the late 19th and early 20th centuries, illustrators and greeting-card makers had transformed the old legend into the image we recognize today: a stork in flight with a newborn bundled in cloth.

The story also solved a practical problem for generations of adults. When a child asked where babies came from, "the stork brought you" was considerably easier to explain at the dinner table.