
Every day I take a walk on the beach. When I first moved to the beach, I didn’t see much order in the different species of birds I observed, but over the years, I’ve observed how birds share the space and the resources that is offered to them here. They do this in many ways, but I’m simply going to talk about zones of the beach, actual physical space that the birds occupy. No doubt this is because they are foraging for different foods, but sometimes it is because they have adapted to forage for the same resources in different manners. There was a famous study done by Robert MacArthur in which he showed that even though five different species of warblers were all after the same resource, they were able to partition this resource by occupying different zones in the tree. This isn’t entirely what’s going on here at the beach, as some birds are simply after different resources, but sometimes the same resources are partitioned by different birds. The result is bands of activity where certain birds can–and cannot–be found.
For a little reference, here in La Serena, the beach is part of a rich kelp forest belt that reaches from Antartica all the way up to Alaska. Some anthropologists call this the Kelp Road which ancient indigenous peoples may have followed from Asia all the way down to the oldest evidence of human occupation in the Americas: Monte Verde, not far from the city of Puerto Montt in the south of Chile whose human occupation has been dated to around 19,000 years before the present. (If I were feeling a bit of Chilean pride, I would say that the first Americans were Chileans, but, well, that’s a bit of an anachronism.) Evidence of the site shows that these ancient peoples relied heavily on the resources of the kelp forests with a diet rich in mollusks and sea weed (they were eating locos and scallops and cochayuyo, just like modern Chileans). This rich resource also breeds an array of wildlife.
The reason for this plenitude is that the cold, polar waters of the Humboldt Current push nutrients to the surface and feed a plethora of ocean fishes and organisms. The base of the food web on the beach consist of clams, scallops, and crabs, which in turn require a healthy kelp forest. Fish are also plentiful as are various insects that feed on the kelp when they are washed ashore.
But as rich as the resources are, they must be shared. While we tend to think of nature as being rife with conflict and competition, it’s also important to think of animals as cooperating. Fighting is dangerous and most animals will avoid a fight if they can. If nature was as cut throat as some people believe, every visit to the beach would be a ringside seat to a blood bath. Instead, animals learn to live with each other. Evolution favors peaceful co-existence over warfare.
Continue reading “Ecological Niches at the Beach”