But there is some controversy over what kind of bird it is.

There is no doubt whatsoever that the bird was a finch. However, what kind? Most likely a house finch, because they are common, and the most likely to live in a big auditorium thingie and not be fearful of people.

A pic of the bird is above. Here is another:

What do you think it is?

An oystercatcher is a wading bird of the family Haematopodidae, distributed in one genus, Haematopus. As is the case with many coast loving birds, there has been confusion about the limits of the 11 or so species known to exist worldwide. That itself is an interesting story (Hocke 1996), but one we will not go into now.

Adult coastal oystercatchers (some species are not coastal) eat all sorts of animals found in the intertidal zone, including shellfish of all sorts, depending on availability. They get their name from their tendency to prey on bivalves (including oysters). Oystercatchers have long heavy beaks which allow them to open these bivalves using various methods (de Hoyo, 1996). At least one method they use for this is to jam the beak into the bivalve and cut the muscle that normally would be used by the bivalve to “clam up.” This strategy is thought to be dangerous, because if the bivalve closes on the beak, then you’ve got this damn bivalve attached to your beak for the rest of the day. If the bivalve in question happens to be attached to the substrate (as are oysters and mussels, typically), then the Foraging Fail is more serious; The bird may have shoved its head under water to get at the bivalve. If not, the tide may be on its way in anyway. Either way, the bird may drown.

Here’s the interesting evolutionary story, which has to do with development.

Adult oystercatcher photo by Steppeland Click here for attribution

Adult oystercathers have a long beak and long legs to facilitate intertidal feeding behaviors, including wading and bivalve predation. But one method of bivalve predation is potentially deadly. So, baby oystercathers have to learn how to do this. Trial and error is not an option. The very first error a baby oystercatcher makes may be its last earthly act before going off to oystercatcher heaven (and there is no oystercatcher heaven). Instead, they must learn using some other learning method. One might expect oystercatcher genes to be selected to make oystercatchers automatically good at this dangerous act. The problem here is that the neural mechanisms underlying the process are higher order integrative systems using a wide range of sensory inputs and motor commands. Organisms with brains can’t evolve pre-programmed genetically tuned neural mechanisms that operate at any level of detail. The brain that runs this finely tuned process must be shaped by experience (learning).

What we see in nature is this: Baby oystercatchers follow their mothers around all day, every day, for many days, watching, watching, constantly watching. They internalize what they are observing, and after many instances of observing the bivalve predation technique, are able to do it.

Baby oystercatcher Photo by Haukur H. Click here for original

That part is interesting; Oystercatchers are an example of evolution NOT solving a complex behavioral problem by pre-programming neural circuits at a fine level of detail. This conforms to what we know about how brains develop (Deacon 1997). It is very difficult or impossible to pre-program complex cortical functions such as language, general intelligence, mathematical abilities, or even something simpler like catching an oyster using genes coding for neural connections. Rather, experience (learning, environment, culture) shapes the brain during development.

And, this part is also interesting (and in relation to oystercatchers, most interesting): The baby oystercatchers, while following around their mothers with their brains being shaped by experience to attain the appropriate skill level, retain a small and ineffective juvenile beak. The babies are incapable of trying what may well be fatal until some time in their development when a hormonal shift occurs, causing their beaks to grow to adult size. It did not have to be this way: It is not true that baby birds typically have non-adult beaks until the last minute (though there is a wide range of developmental trajectories for bird beaks). The long-retained small beak, caused by the timing of hormonal development, facilitates learning in the particular way that conforms to the overall oystercatcher adaptation.

Well, that certainly is a nice story, but it is also based on common knowledge of bird behavior, development, and ecology. How do we really know that oystercatchers actually risk death while foraging for bivalves? Well, we know this because we know this. This is probably one of those pieces of knowledge that is generally known by natural historians, is written down as a generalization in a number of authoritative or semi-authoritative books, and for which there is a handful of anectdotal examples buried somewhere in the pre-PDF, pre-Google, pre-Medline ancient literature. And therefore, lost in obscurity and of no possible value.

But wait, there are scholars who still read actual books and printed journals! And it turns out, this can be useful and interesting. There is indeed an ancient, obscure anecdotal case, and it is brought to us via Tetrapod Zoology Blog. In Clam attacks and kills oystercatcher, Darren Naish describes a publication from 1946 in The Auk (a classic bird journal) in which a brief account is provided of an oystercatcher having got its beak stuck in the clam, as it were.

In this case, an adult Haematopus palliatus (American oystercatcher) got its beak stuck in a Mercenaria mercenaria (hard shelled clam) in South Carolina, in 1939.

It drowned, and the soft tissue of its neck was scavenged by crabs. What a way to go.

Baldwin, W. P. (1946). Clam catches oyster-catcher The Auk, 63, 589-589

Deacon, T. (1997) The Symbolic Species: The Co-Evolution of Language and the Brain. Norton.

Hockey, P (1996) Family Haematopodidae (Oystercatchers) in del Hoyo, J.; Elliot, A. & Sargatal, J. (editors). (1996). Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions. ISBN 8487334202

del Hoyo, J., Elliott, A. and Sargatal, J. (1996) Handbook of the Birds of the World. Vol. 3: Hoatzin to Auks. Lynx Edicions, Barcelona.

In this installment of How the Loon Terns we will look at breeding success.

In this installment of How the Loon Terns we will look at breeding success.

Common Knowledge: When a pair of loons fails to breed, it is because they have lead poisoning. Last year the pair of loons failed to breed. I mentioned this to a bird expert … a trained ornithologist who is actually working part time on loon conservation and who works for a major research institution. We were chatting at an educational bird display event and she was showing off some raptors. She did not know that I was a scientist, loon-lover, blogger, but she did know that I did the lake/cabin thing. That is important context to what she told me. She indicated that lead poisoning was the reason, caused by hunters using lead shot and anglers using lead weights. The idea here is that when loons go down to the bottom of the pond or lake to get stones for their gullets, they often pull up these bits of lead. This significantly affects their health. When I suggested alternative explanations, she politely told me that no, it was the lead. “Trust me,” she said. “Sure,” I said. “Right,” I thought.

Now, I’m sure this is a real problem, and I support regulations against lead in hunting and fishing. In fact, I can’t believe we are still using lead. But I’m not so sure that lead was the issue here. The following observations argue against it:

1) Last year the lake was at its lowest in any one’s memory. Everyone’s memory is that the loons produce one or two offspring a year, but last year it was zero and the year before one. Last year was the lowest lake level, the year before the second lowest. The lake level determines the ecology of the bay including the inlets and shallows, and the extent of the marshes. A very large area that is normally shallow water became marsh last year, and the loons do not really forage in the marsh. So, the change in ecology should be considered as a possible factor. I’m not saying it is a factor, and I’m certainly not insisting that it is the factor. I’m just sayin’.

2) The loons live over rocky and gravelly substrate. If you grab stuff off the bottom, it will be sand with gravel (between rocks). While there is some duck hunting right in the vicinity that the loons nest, and there is lots of fishing around here (so I have no doubt that lead is a problem) this bay has a lot of non-lead gravel to offer. I hypothesize that lead is more of a problem in waters with little natural gullet-suited gravel.

3) As mentioned in point 1, the loons seem to always breed except that one year. I would think that if lead was a chronic problem with these loons there would be many years with zero and some with one offspring, rather than most with two and a couple with one (except this one year with zero).

I want to point one thing out that is very important: I noted earlier that one loon in the pair might have changed two years ago. That pair raised one offspring. Last year I did not see a change, and this year I did not see a challenge to the pair by an interloping loon, but this does not mean it did not happen. So, it could be that both adults in the pair are constantly being poisoned by lead, and when two longer-term loons are resident, they eventually have low success, but when one of the two is relatively “fresh” they have better success. Or, it could be that an interloper who takes over (say a female) for one of the pair could be from a place where more lead is consumed (a muddy bottomed pond where the lead shot is more likely to be consumed because there is not much gravel). And so on. My point being that my observations of what happens here on this bay may be only part of the lead poisoning picture.

I conclude that while lead is important, I’m being fed some rhetoric from the bird conservation people who want to emphasize the lead problem at the expense of adherence to the science. I don’t blame them. The average person has a hard time with nuance (I wonder why???) so they have to be beat over the head with simplified version of the facts. Many hunters or anglers may be quite willing to use uncertainty as an excuse for continued use of lead sinkers or lead shot. I do think, however, that this sort of zeal on the part of bird conservation people is fairly common and not generally a good thing.

Next: A look at boating and habitat loss.