One of the sad, but immutable, laws of nature is that if you are not at the top of the food chain, you are in someone else's. On Skomer Island, this is something that becomes painfully apparent the more you watch nature in action.

Puffins, for instance, predate sand-eels. But puffins are not on top of the food chain. Both directly and indirectly they contribute to others.

Peregrine falcons breed on Skomer on cliffs adjacent to some of the largest clusters of puffin burrows. A bit like having a maniac ultra-high speed cannibal living two doors away, waiting for you to leave the house.

Gulls predate puffins in various ways. Skomer has populations of both lesser and greater black-backed gulls (BBGs). The greater ones can take on a full-grown puffin, and will certainly take chicks given the opportunity. While the lesser BBGs rarely take on an adult, they will go after unguarded chicks too.

One of the not-well known aspects of the lesser BBGs is that they will attempt to steal cargoes of sand-eels that the puffins bring back to feed their chicks (a form of kleptoparasitism). Drew and Richard pointed out to us that gulls can spot puffins with sand-eels much quicker than we can. They will jump after, hassle and harry returning puffins trying to force them to drop their cargoes before they can be given to the chicks. They'll even stick their heads into the burrows to try to get the fish (or the chick if the parent is not effective at protecting it).

Jackdaws also take advantage of any dropped fish. They always hang around where the gulls get at the puffins, pouncing on anything the gulls miss.

Puffins are not the only victims of the gulls. We saw an oystercatcher that sat a lonely vigil on top of a broken-down stone wall. It was probably guarding a nest from the lesser BBGs. Every so often, it would go up in the air to mob a lesser BBG that posed a threat.

Perhaps the saddest sight is the corpses of Manx shearwaters that dot the ground wherever you walk. There is a huge population of these birds on Skomer: the better part of three-quarters of a million birds. While they are amazingly adapted for life at sea, they have to come in to land to breed. This is where they can fall victim to greater BBGs. The BGGs can make short work of the Manxies, devouring anything edible, and leaving the stripped corpses littering the ground. Manxies have adapted to predation through a nocturnal lifestyle, but a bright moon or lights from shipping can show them up and leave them vulnerable. While I was on Skomer, the moon was bright and I never even heard them flying in, as they stayed clear of being seen by their predators.

It is important to remember though, that however brutal all this undoubtedly is, the puffins and shearwater colonies, as a whole, are doing well. This year and last, over 40,000 puffins were counted on the small island, an immense increase in the numbers just a few decades ago.