You maintain something when you keep it in its current state. For example, you might maintain a friendship with someone, or maintain your house to keep it in good condition. This is called carrying out maintenance. The soldiers in the picture are maintaining grave sites.
Marching is a way of walking that is brisk and formal. Soldiers march together with their steps in time with each other. See also: March, the calendar month.
To meander means to take an indirect or wandering path. For example, rivers aren't often straight lines from one body of water to another, instead rivers twist and turn in a meandering fashion.
You measure something when you find out how big or heavy it is. People might measure distance, weight or size.
Birds or animals migrate when they all move to a new area at the same time. Migrations happen with the seasons at the same time each year so the birds or animals follow their food source. Sometimes they travel an incredible distance - some kinds of bird travel halfway around the world!
You go out and mingle when you go out amongst other people and talk to them. Mingling is a great way to meet new people.
Mixing is a way of combining two or more things together so you cannot easily tell what went into the mix. You make cake batter by mixing the ingredients together, and you make new colours of paint by mixing different colours together. Food described as 'mixed' like mixed candy or mixed nuts is made from several different kinds of food mixed together. The picture is of someone mixing several different colours of paint together.
You moor a boat when you tie it to something on the shore so it doesn't float away. See also moor, the swampy area.
Moulting, also spelt molting, is when a bird or animal loses some of its feathers or fur so that it can grow new ones. Birds and animals usually moult on the change of season, so that they can grow a thick coat for the winter, or shed their winter coat when the weather warms up.