Tuesday, December 13, 2016

A brief meditation on observation of the natural world

For years, we’ve been counting birds down here and trying to draw conclusions from what we observe. Back in the late 1990’s, I read about a Grebe die-off in California and sure enough, months later we had hundreds of little emaciated bodies washing up on the shore. And since that time, we’ve never gone back to the amounts seen before the event. In other years, we’ve observed crashes of the Brown Pelican and Double-crested Cormorant populations that I wrote gloomily about as evidence of the destruction of the Gulf fishery and the doom of both species. But as time went on, the birds came back and today they appear to be about the same as ever.
This year though we seemed to be down on both those two and the local Blue-footed and Brown Booby populations. In the case of the former two, decent numbers seen from shore but far less than the thousands I normally count. The observed numbers of the latter two though has been downright depressing. Instead of hundreds, I’d only managed 4 birds in the whole 10 days of looking. They simply were not present.
So today my friend Doug and I powered up a friend’s $50 aluminum boat and took our annual 3-hour tour of Bahia San Francisco. The slightly overcast sky made it a bit nippy as we headed out to our first stop, passing a local fisherman snorkeling for rock lobsters and a single sea lion basking on the surface, a single fin held straight up to the sky.
Closing in on the big rock locally called “Haystack” the reason for the missing birds was immediately obvious – hundreds of Blue-footed Boobies, Brown Pelicans and Double-crested Cormorants clinging to every niche on the side of the white-washed rock. Many hundreds in fact. My initial conclusion was that the food must have moved out of the bay and so the birds were resting further out and closer to it.
Having counted this host, we moved on to the next two rocks where we ticked off the expectedly small group of Pelagic Cormorants and a few more Pelicans. Not a surprising result, one way or the other. Our last stop was a long, flat volcanic seamount closer to shore and known for a small population of wintering Savannah Sparrows. We passed another sea lion enjoying the day on the way over.
Doug told me that he’d been out here a few weeks earlier and seen more Pelicans that he’d ever seen before. Arriving, it was clear he was not exaggerating – the place was covered from one end to the other with thousands of them. We landed and stopped to watch a Least Sandpiper picking its way through some shore seaweed, dining on gnats and almost walking right up to us. The Savannah Sparrows were just where I’d left them last Christmas.
Climbing up the rocks we found ourselves standing among dozens of Pelican nests, each still containing eggs. A Yellow-footed Gull was smashing one on the ground and flinging the contents into the air. And that’s when it dawned on me – the birds weren’t missing because of depleted food or decimated populations, they were missing because they were nesting for a second time this season. Spread out over the top of the island was a vast colony of Pelicans sitting on their surprisingly neat nests, incubating their eggs. We’d unintentionally caused a bit of damage by chasing a few birds off their nests and creating an opportunity for the Gull to jump in and grab a snack. We backed off quickly and watched as the birds returned.
There are two lessons for me from today, the first being that it’s tough to draw a meaningful conclusion from what seems to be clear information. The birds are gone, therefore there are less birds, and less birds probably means disease or food supply problems. Had we not gone out to sea, we never would have found either of these groups and I would have written a completely different update for our count when it’s submitted.
The second lesson is a bit subtler – there is some reason why these birds are suddenly capable of nesting twice in a season. I’ve been out to that little island just about every December for 20 years and never has it been covered with nesting birds. Nesting is a spring thing, designed to give the chicks the greatest opportunity for survival, having grown to a reasonable size before the dodgy winter weather begins. Not this year - clearly nature is allowing a second chance, and that can only be due to adequate food and warmer weather, both no doubt due to our changing climate. An ancillary bit of data confirms the temperature theory – we now have Sand Fleas chewing on us at this late date, something we never had before.

The good news is we have very solid populations of these species. The bad news, the cause is probably not good. It seems as the Arctic melts, things get rosier elsewhere. Well, at least for now. 

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