Geese can smell the odor of man better than any other animal can
There are two kinds of geese: wild geese, which fly in order high in the sky; and domestic geese, which live in villages, clamor, and maintain themselves with their beaks. Geese mark the night watch by repeated cackling; geese thus warned the Romans of the attacking Gauls. Geese can smell the odor of man better than any other animal can.
The goose can signify men who are prudent and look out for their own safety. As the cackling of a goose saved the city of Rome, so the warning voice of a brother warns his community of disruption by the wicked. The sense of smell of geese represents the wise man who knows of other men by their good or bad reputation.
Pliny the Elder [1st century CE] (Natural History, Book 10, 26-29): Geese keep careful watch; the cackling of geese warned of an attack at the Capitol in Rome. Geese may have the power of wisdom, as shown by the story of a goose who was the companion of the philosopher Lacydes and refused to leave his side. Geese are valued for their liver, which is a great delicacy, and for their feathers, especially the soft inner down. Geese come on foot to Rome from Gaul; if one gets tired it is moved to the front, so that it is forced to continue by the press of the geese behind it. Medicine can be made by mixing goose fat with cinnamon in a bronze bowl, covering it with snow and letting it steep. Only the ostrich reaches a greater size than the goose. Geese kept in a fishpond lose their flavor, and stubbornly hold their breath until they die.
Saint Ambrose [4th century CE] (Hexameron, Book 5, chapter 12.44): Who does not marvel at the nightly sentry watches of the. geese, who give evidence of their vigilance by their constant cackling? That was the way in which they defended even the Roman Capitol from the Gauls. You, Rome, rightfully owe to them the preservation of your empire. Your gods were sleeping, but the geese were awake. - [Savage translation, 1961]
Isidore of Seville [7th century CE] (Etymologies, Book 12, 7:52): The goose (anser) took its name from its similarity to the duck (ans), or because it swims frequently (natandi frequetia). Geese watch at night and give warning with their noise; they can smell humans better than any other animal can. Geese warned Rome of attack by the Gauls.