Introduction to Habituation, Imprinting and Conditioning - YouTube

simple animation illustrates the meaning & use of the terms.
very helpful for explaining the concepts.

BTW - one error: ducklings imprint on the first MOVING object; not any inanimate object.

Moving or moving away?

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Moving or closest object moving away?

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i haven't a clue if anyone has tested to see if it matters. When they first hatch, there is a span of 12 to 24 hours
over which the clutch hatches & the ducklings recover from struggling to exit the egg, plus stand erect strongly -
they've been curled in a hoop in the egg, their muscles need time to straighten & strengthen. But the duck cannot wait
too long - dry land is not safe, the babies need water to drink, swim in, & feed from, as soon as possible.

during those hours while they wait for stragglers to hatch & get on their feet, i am sure she presents her face often,
as well as her tail - & i don't know whether face or tail matters, to the duckling, or if approach or retreat
is preferred instinctively.

but at some point the duck must conclude that any eggs left are hopeless, her brood are fluffy now & all are
walking - they leave on a forced march to the nearest body of water, the ducklings are still being fed
by their yolk-sacs which will be depleted soon, so they have to hurry, & also evade any predators along the way.

another thing that was not mentioned:
the ducklings TALKED while still in the egg to each other, & to their mother - calling helps to co-ordinate the timing
when the eggs hatch, the excited cross-chatter leading up to a collective hatch is an important factor.
and they recognize their mother's voice; if this is a species where the drake also broods, they recognize
their father's or stepfather's voice.

movement is important, but a familiar parent's voice would be another clue if they were hatched amid a flock.