We were standing holding on to the railing of the catamaran as it pitched through the indigo blue of the deep waters off Kona. I mentioned to my dad that I hadn’t seen a gull since we had arrived on the islands. If this had been back on a mainland coastline, there would have been numerous gulls.
“In fact,” I said, “I haven’t seen any marine birds here.” Just after I said this, a large blue-billed Red-Footed Booby swept past the catamaran, swerved and then returned to give us the once-over before sweeping off into the dusk. It didn’t beat a wing, but sailed efficiently and smoothly through the chill brisk breeze. Just afterwards I saw two other marine birds, probably shearwaters, cutting swiftly through the air just above the waves. They didn’t tarry either but flew rapidly away and disappeared. These seemed to be birds superbly adapted to this oceanic habitat, with beautiful functional lines and structure.
We never did see a gull during the two weeks that we were in Hawaii for my daughter’s wedding. This was something that puzzled me. My dad said that there probably wasn’t enough food to support a population of gulls. I was dubious and did a search which is summarized below:
1. The Hawaiian islands are an isolated group. This is not a reason. Yes, the islands are isolated but gulls DO reach the islands and probably have throughout the past millenia. The original colonizing honey creepers reached the islands and underwent an adaptive radiation into many niches. How strong a flier are honeycreepers? Not as strong as gulls I suspect.
2. Gulls can’t drink salt water because they don’t have desalination glands. Wrong, gulls can drink salt water and they do have these glands. However there are freshwater streams that would offer a freshwater source even if they couldn’t drink salt water. This is not a valid reason.
3. Gulls aren’t found very far from large land masses. This isn’t an answer, but simply another observation on the scarcity of gulls on islands. Gulls can and do make it to the islands and have most likely for many years. Why haven’t they established breeding colonies here?
4. Gulls frequent the shallow waters of the continental shelves and their food habits reflect this. Ok, this isn’t very clear. Does this mean that the deep waters about the islands do NOT have a sufficient amount of food for gulls? Just to my eye there was an abundance of fish, but perhaps they weren’t sufficient to support a population of gulls.
5. Another source: “The lack of sea gulls around Hawaii is due to the absence of a breeding population OR the islands, which in turn is because the food resources normally eaten by gulls are absent. While the fish fauna around Hawaii seems abundant, in reality it is considered depauperate. Although, several terns thrive on the islands, gulls are primarily temperate species and only scattered, wandering individuals show up in the tropical Hawaiian chain.” Huh?
According to number five my father was right…not enough food. Somehow this still seems inadequate, especially since I read one estimate that at any one time there were fifteen million sea birds of 22 species flying over the Hawaiian islands. If I hear of a better explanation, I’ll let you know.