Mudflats · Coconut CoveScience for kids

Why do birds flock to bare-looking mudflats?

In short: Mudflats are wide stretches of soft mud uncovered at low tide. They look empty, but the mud is packed with crabs, shellfish and worms, making it a seaside restaurant where flocks of migrating birds stop to feast.

How it works

Rivers carry fine mud to the coast. In calm bays and estuaries, where the water slows down, the mud settles and builds up over time into mudflats. The sea covers them at high tide and uncovers them at low tide, bringing in fresh nutrients and food each time.

The mud is full of hidden life. Crabs dig burrows, shellfish bury themselves and filter food from the sea water, and worms wriggle through the mud. The tiny holes, little mounds and bubbles on the surface are signs of the creatures living below.

For migrating birds, mudflats are refuelling stations on very long journeys. Different birds have different beaks: long-billed birds probe deep into the mud for worms, while short-billed birds peck crabs and snails from the surface, so they can share the feast.

Where to see it in New Zealand

Every spring, thousands of bar-tailed godwits, or kuaka, fly more than 10,000 kilometres non-stop from Alaska to New Zealand's mudflats, and head north again around March. Pūkorokoro Miranda on the Firth of Thames and Farewell Spit are great places to see them.

Try it together

At low tide, go with an adult to the edge of a mudflat and stay on firm sand, out of soft mud. Wait quietly for a few minutes. Can you spot holes, bubbles or crab tracks? Does a little crab peek out? Take binoculars to watch the birds.

Kids also ask

Why do mudflats smell like rotten eggs?

The mud has very little oxygen. As bacteria break down dead seaweed and creatures, they give off a gas that smells like rotten eggs. It is a normal mudflat smell and a sign of busy life in the mud.

Is it safe to walk on mudflats?

Take care. Soft mud can trap your feet, and the tide can come back in quickly. Always go with an adult, check the tide times first, stay on firm ground and don't disturb feeding birds.

In the game, “Mudflats” is a nature card on Coconut Cove.

Your child finds this card by reaching the right place or meeting the right weather on the island, and lights it up by answering the question on the back. Tap the button below and the game shows your child which island it is on and how to find it. Mochi Isle is a browser learning game for ages 5 to 18; the main island and the daily lesson are free.

Find “Mudflats” on the island ↗ All cards from Coconut Cove