When geese are feeding it is not specified as far as I can tell, but during nesting it is the male who does the guarding.
Wary - Alert for danger. Often while the flock is feeding, individuals will take turns acting as sentinels (neck erect), warning others of impending danger (Bent 1925).
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The Canada Geese are fond of returning regularly to the place which they have chosen for resting in, and this they continue to do until they find themselves greatly molested while there.
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Thus, on some of the great sand-bars of the Ohio, the Mississippi, and other lase streams, congregated flocks, often amounting to a thousand individuals, may be seen at the approach of night, which they spend there, lying on the sand within a few feet of each other, every flock having its own sentinel.
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Whilst the group, called a gaggle, of geese are feeding at least one goose will stand guard, a sentinel against any predatory threat. They have an incredible sense of sight and hearing and issue out a very loud warming honk in the event of danger. Wherever geese congregate other birds will visit the pond or lake to take advantage of this early warning system.
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As compared to during nesting times,
Geese are perennially monogamous, meaning that one male and one female form a lifelong pair bond. Like ducks, paired male geese protect their mates from harassment by intruders, but their larger size allows ganders to defend against not only other males but also many predators. While male ducks wait on nearby ponds to rejoin their respective mates following egg laying and during incubation breaks, ganders stand guard in the immediate vicinity of the nest. In further contrast to ducks, male geese remain intensely territorial until the eggs hatch and then assist the female with brood-rearing duties.
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Geese will appear in pairs during nesting season. A solitary goose
typically indicates that a nest is in the vicinity and "he" is
standing guard.
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The male goose will stand at guard a distance away from his nesting mate, so that he does not attract predators to his mate. We get numerous calls during nesting season about “a goose has been standing in one spot for days, it won’t fly away; is it OK”? This is the male goose standing guard over the nesting goose. If a predator approaches the nesting area, he will attack it, to distract it from discovering the nesting goose.
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She covers them to keep them safe for predators. With a gentle sound from her, the goslings know they are being called to safety, and all scurry under her wings where it is safe. The gander, the father of the goslings, stands watch over the little ones and his mate, very proudly, his strong neck raised high and looking about in all directions, guarding and protecting them all.
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Fun fact, humans sometimes use geese to guard things.
On modern farms, geese are said to be good deterrents to predators of other domestic fowl,1[13] and snakes. A handbook on industrial security recommends them for protecting warehouses and other isolated physical assets.[14] They are reported to have been used to guard United States Air Defense Command installations in Germany;[15] Ballantine's Distillery in Dumbarton, Scotland; and to protect a police station in Xinjiang, China
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