While in South Africa, Linda and I observed oxpeckers eating ticks off the back of and also from inside the ear of a rhino. That is a form of symbiosis.
On occasions I’ve seen magpies and starlings feed off the back or heads of deer and cattle. Yesterday I came upon two starlings each standing on the head of a cow.
Here is a photo of the two cows, each with a starling on their head. It’s difficult to see the starling on the head of the all-black cow, but look close, you’ll see it. The beak stands out.
Not sure if they were after flies or ticks, but there were plenty of flies. When a symbiotic relationship benefits both parties, it is called mutualism. Had to look that up.