Swallow

Swallows are presented in Silent Spring as birds whose decline makes the effects of pesticide use visible in the everyday landscape. A Wisconsin naturalist contrasted skies once full of swallows with their near absence four years later, and identified two possible links to spraying: the loss of insect food and the poisoning of insects that remained.

Feeding and Exposure

The book describes swallows as aerial feeders, straining insects from the sky in a way compared to herring filtering plankton from the sea. Their dependence on airborne insects ties their fortunes to the abundance and condition of that food supply: spraying may harm them by reducing insects, or by leaving poisoned insects for birds to eat.

Reported Decline

A Wisconsin naturalist recalled that swallows had been plentiful overhead four years earlier, but were now seldom seen. The report does not settle whether the change resulted from a shortage of insects, poisoned prey, or both. Its force lies partly in that uncertainty: the disappearance is observed directly, while the precise route from spraying to fewer birds remains unresolved.

Significance

The swallows' decline belongs to the book's wider account of harms that can be difficult to isolate in a single dramatic incident. Their reported scarcity connects pesticide use to changes in the food web and turns a familiar feature of the sky into evidence of ecological disruption. The naturalist's account also preserves the limits of what could be concluded from observation alone, distinguishing the evident loss from its possible causes.