Helen Alexander, of Wellington, asks :-

How do birds find worms under the ground?

Kevin Burns, an ecologist at Victoria University of Wellington, responded.

It turns-out that most birds don’t find worms underground at all. They wait until worms are forced-out into the open to snatch them up. Most earthworms live in burrows that they excavate beneath the soil surface. This usually keeps them safe from hungry birds, most of which aren't adapted to dig for their next meal.

But lucky for birds, earthworm burrows fill with water when it rains heavily, which forces them to come to the surface to avoid drowning. Birds often take advantage of rainy days to gobble-up as many worms as possible, which is why you often see large flocks on grassy paddocks after heavy rain. In this way, most birds wait for earthworms to come to them, rather than the other way around.

However, scientists have come to expect the unexpected when it comes to New Zealand’s birds. Unlike forest dwelling birds elsewhere, kiwis actively hunt beneath the soil surface. Kiwis have exceptionally long bills, which they use to poke through the soil surface to infiltrate the homes of earthworms and other invertebrates hiding below. They don’t use their eyes much, because they forage mostly at night. It’s also hard to see anything that’s buried beneath the ground, even during the day. They instead use a highly acute sense of smell to find their next meal. They are the only birds on the planet to have nostrils at the end of the bills, so they are exquisitely adapted to locate prey buried beneath the soil surface. Furthermore they have long whiskers that may help them feel for worms burrowing below.

So in the end, the answer to your question depends on whether or not you’re a kiwi, whose long nostrils and whiskers are an exception to the rule.