Lead Poisoning and Loons: A skeptical look

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This is the continuation of a discussion of loons, skeptically viewed. I am not skeptical about loons themselves. I know they exist. In fact, I just spent the last half hour watching Mom and Dad loon (whom I cannot tell apart, by the way) feeding Junior I and Junior II (whom I also cannot tell apart) what I have determined to be mostly crayfish, but also the occasional minnow.

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.

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17 thoughts on “Lead Poisoning and Loons: A skeptical look

  1. Could various other pollutants that act as endocrine disruptors alternatively be a problem? Our sewage systems aren’t equipped to remove medical residue from effluent.

    “Simplified version of the facts”: I heard Robert F. Kennedy Jr. speak once, and cringed every time he referred to mercury as a “brain poison”. (Sure, I guess you could call it that but the brain isn’t your whole nervous system. Condescend much?) He was talking about mercury from coal burning plants. I kept waiting for him to mention vaccines but he never did.

  2. Sceptical of “scientific” claims?

    I do not deny that anthropogenic carbon dioxide has influence on the climate, but a question by me to Discovery channel last year and a science blogger to please show a comparison between naturally released carbon dioxide (volcanic and other) and anthropogenic fell pretty much on deaf ears.

    If that is the way so called “scientists” treat legitimate questions, no wonder people tell them to fuck off with their various and quite frequently changing claims.
    The worst examples of “science” are the various claims as to the health of different foods or food additives.

    Scientists very often – and especially in fields relating to human and environmental health – are riding hobby horses and pressing a narrow agenda without often considering alternative hypothesis, maybe because they think that pressing their point – as in the lead affecting fowl – can achieve some “good” by neglecting alternative explanations.
    Unfortunately, this attitude very often leads to one thing – distrust what science has to say. Crying wolf once too many.

  3. IANALB (I am not a loon biologist), so I am not current on the evidence for lead poisoning. It is possible that there are other lines of evidence, in addition to the observation that humans are putting lead into the environment, that causally links lead to low reproductive success in waterfowl. It’s possible that wildlife biologists have compared tissue samples from successful and unsuccessful loons, or fed lead to captive birds, or measured spatially correlated reproductive success and lead concentrations in substrate, or found more lead shot in the digestive systems of unsuccessful breeders.

    Peter dismisses the conclusions of all scientists because he is unfamiliar with the evidence. Just because Peter is ignorant doesn’t mean that the conclusions of scientists working in the field are wrong.

    It’s good to be skeptical, but sloppy to draw conclusions about loon biology based on one breeding pair. So let’s look at the data before we dismiss any hypotheses.

  4. I did get into an interesting discussion with an Audobon Society dude once about 25 years ago. He was bemoaning how evil agriculture was killing the poor little duckies and gooses and pointed to historically small waterfowl production rates in the mid 1980s as evidence. I asked him if he was aware that the region was experiencing its worst drought since the 1930s and that farmers were suffering as bad as the ducks. He wasn’t. I predicted that when the rains returned, so would the ducks. Well, wide swathes of North Dakota have been in a state of semipermanent flooding since the early 90s and we have more ducks and geese than we know what to do with.
    I think Greg has the proper response, propose an alternative or a null hypothesis and collect more data to evaluate which is more accurate.

  5. Well, wide swathes of North Dakota have been in a state of semipermanent flooding since the early 90s and we have more ducks and geese than we know what to do with.

    I wonder what you’d do then, if saypintail populations hadn’t dropped by 77% since 1940.

    Sure, flood years will lead to increased production, while drought will cause decreases, both excursions *around the declining trend*.

    And, yes, agriculture is a big culprit. The conversion of natural wetlands – mostly potholes in the breeding range of pintail in the dakotas – to wheat fields obviously ends breeding in those areas.

    Now, there have been various conservation efforts, for instance, to pay farmers to maintain potholes as wetlands rather than farm them, which have helped slow the decline.

    Yet … the 77% decline of this species is real.

    Pintail are apparently the worst affected “puddle duck” in the dakotas, but I’m not entirely sure, as I only spent a few minutes in google looking for the above information (easy for me because I knew of the problems with puddle ducks, disappearing puddles (potholes), and pintail in particular beforehand).

    More on pintail populations:

    The North American Northern Pintail population was estimated to be about 6 million in the early 1970s. The recent population trend is worsening; the spring 2005 breeding population was estimated to be only 2.6 million birds, which is 38% below the long-term average. Population trend analysis for this species using data from both the Christmas Bird Count and the Breeding Bird Survey confirms that the species is in significant decline.

    This doesn’t break out trends for the dakotas but I don’t have any particular reason to believe that things are any better there than in the rest of their range.

    And I’m certainly not going to take anecdotal comments on the intertubes as being authoritative …

    While populations of other prairie nesting ducks increased dramatically following the droughts of the late 1980s and early 2000s, pintail populations remain 38% below their long-term average and 53% below the North American Waterbird Management Plan goals.

    Hmmm … maybe you actually don’t have more of this species than you know what to do with …

    Even though the estimated number of prairie wetlands (May Ponds) indexed by the May Survey increased to record high levels in Canada and the U.S. subsequent to the long drought of the 1980s and early 1990s, pintail populations did not increase as expected based on the historical relationship between these two indices. Each peak in pintail numbers since that in 1955-56 has been successively lower than the one before and each low point (1960s and 1980s-early 1990s) has been lower than the one before.

    No, probably not…

    I’ll give you “ducks” in general, though, I’m picking on pintails because they’re doing poorly.

    Anyway, not just flooding but conservation efforts have helped other species rebound.

  6. It is possible that there are other lines of evidence, in addition to the observation that humans are putting lead into the environment, that causally links lead to low reproductive success in waterfowl.

    Will, there is evidence linking lead and reproduction drops, but it is not straight forward. Lead and reduced fertility has been linked in other waterfowl, and lead has been identified as a major cause of morbidity and mortality in loons. Simply linking lead to morbidity can indirectly link it to reproduction because reductions in health can be all that is needed to reduce fertility.

    I’m not skeptical about lead. What I am skeptical about is my loons, who do quite well every year.

    I am absolutely not drawing conclusions regarding loon biology on the basis of one breeding pair. I am doing exactly the opposite. I’m critiquing the application of a simplistic (and I think in part strategically motivated) general model from loon biology to explain a single case when natural variation related to feeding ecology and stuff may be a better explanation. I’m problemetizing the normative loon (two offspring a year) and the normative conservation-oriented answer.

    There is a very good possibility that the three Bald Eagles that habitually roost in the trees overlloking the loon’s habitually used nest are more important of a factor than the lead, in this particular case, in this particular bay.

    By the way, the number of states that have illegalized lead weights is growing all the time.

  7. Loons breed at age three. The loons you saw could be age 2 or 1. Lead poisoning will not necessarily cause them to not breed, but it could impact the offspring. I have seen crippled and dwarfed trumpeter swan cygnets that tests found to have high lead levels.

  8. While I can’t speak to the reproductive success, I can tell you we still routinely run into lead sinkers when we do our waterfowl autopsies here in Michigan.

    (In case you are curious, it’s mostly to let our interns look at the inside of a bird. If they are croaked already, no harm, no fowl. Har!)

  9. I know this is an anecdote, but some years ago I was at Walden Pond and went to pick up a pebble and it was a lead sinker with a significant corrosion thickness. It was about a quarter inch in diameter, and likely would be a fatal dose of lead if a bird had eaten it.

    I only went to Walden Pond sporadically, but my cumulative time there was perhaps a few hundred hours. If I could find a lead sinker, a waterfowl likely could too.

    The people with a substantial interest in wild birds are hunters, who also happen to be the ones who inject lead pellets into the environment via gunfire. There are lead free alternatives, there is no reason not to use them except cost. The cost of lead shot and lead sinkers is a tiny fraction of what hunters and fishermen spend on their activities. Switching to lead free alternatives isn’t that big a deal. At some point, lead will build up in the environment due to hunting. Better to reduce that buildup by stopping adding more now.

  10. Well dhogoza if you want to get into dueling ducks …
    Canvasbacks – 16 percent above long term average
    Redhead – 62 percent above long term average
    Northern Shoveler – 92 percent above long term average
    Gadwall – 73 percent above long term average
    Green Winged Teal – 79 percent above long term average
    Blue Winged Teal – 60 percent above long term average
    Mallard – 10 percent above long term average
    Total Ducks – 25 percent above long term average
    Information is here.
    Pintails are doing poorly, but they were only 20 below their long term average in 2008, instead of the 38 percent figure you quoted. Widgeons are also not doing as well as other ducks, but their population is only one percent below the long term average.
    I also noticed that you linked to Audubon’s 2002 Watch List and that the Pintail was dropped from the 2007 Watch List. I would also point out that Audubon does not seem to have a “Birds Doing Well” list.

  11. I should tell my Walden Pond story… which I probably did blog at some point … But for now, just for context: Walden pond does get like a million visitors a year. Most are not fishing, of course. In fact, it isn’t fished all that much. I’ve caught quite a few trout there, across the lake from the main beach. The point being, a lead sinker at Walden could be 150 years old! That pond must be loaded with lead! (Though I don’t think there is much waterfowl hunting there.)

  12. Bug Girl: Thanks for the comment. Yes, in one data set that I don’ think was Michigan but was in some loony state E of MN something like a fourth of the loons found dead (in 1995 IIRC) seem to have died of lead poisoning.

    It probably does not take too many sinkers in the gizzard to kill a bird, considering that in the gizzard they are ground up and digested….

  13. I didn’t hear mention of the size of the lake or if there are wake-raising watercraft on it, but in lakes big enough so that loons can build up enough speed to get airborn, there are sometimes motorized craft. Loons, I understand, build their nests right at waterline in waters that are like what they are instinctually adapted to seek out. PWDs can really mess that up. I’ve heard this seriously mentioned by some field ornithologiests. Any of those little go-devils been toolin’ around your lake in the last few years? Just curious.

  14. PWDs? Yes, there are some. But they do not cause a damaging wake to the extent that water ski boats do. Also, the lake is too cold for PWD’s after the chicks are off the nest. The loon nest, is in an excellent location regarding wakes, and is probably OK, but it is a factor.

    This is a large lake. The total use rate is lower than other similar size lakes, but there are plenty of boats. The lake is large enough (2,200 ha) to have aircraft land on it (they don’t land anywhere near the loons, though).

    I will be addressing boats in a future edition of The Skeptical Loon….

  15. Good Ecology research is damn hard to do, as your pointing out. We only get to study very tiny snapshots of very complicated systems and are trying to deduce generalities.

    Anyway, keep up the posts… they are quite interesting.

    A word on lead shot. There are several very good reasons it is used. It is very heavy (2E=MV^2), it is melts at a relatively low temp (easy to work with), and it is soft (easy to work with and can deform to more efficiently convert kinetic energy into carnage).

    However, all that said, killing a bird with a shotgun doesn’t take a lot of “umph”… and steel shot works perfectly fine and should be used by all hunters. There is more of a valid argument regarding bullets.

    Lead fishing weights are just dumb. Get a pair of pliers and untempered steel (or just iron) works fine.

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