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Feature

Black Robin
-- Alive by Accident?

The saving of the Chatham Islands black robin is a wonderful success story, but it may well have succeeded in spite of
conservation science, rather than because of it.

Ian G. McLean

Conservation biology is undergoing a revolution. It has moved dramatically from a subsistence existence as a concoction of natural history, local issues and a few dedicated individuals, to being a quantitative science with a sound theoretical base, global applications and a network of professionals.

But there is a long way to go. According to my dictionary, science consists of systematic and formulated knowledge based mainly on observation, experiment, and induction. This conceptual approach is frequently incompatible with the doing of conservation. Why? Because pressure to "do something" in the face of crisis supervenes any attempt to do precisely those things that constitute good science.

How can one experiment when sample sizes are too small to provide statistically testable results? What is the point of observation when one is dealing with a relict population in degraded habitat? Why gather systematic information when the choices are immediate intervention or extinction?

Right here in New Zealand, we have an example that is already a classic in the work of modern conservation -- the black robin, a species which by rights should have been written off. Surely it was irresponsible to expend resources on a species that in 1980 was clearly extinct in all but name. The programme might even have been comparable with that well known Air Force house.

Hold on. The black robin story is one of success, has been applauded across the world, is the flagship of the New Zealand conservation movement. Black robins are saved, or at least no longer face the threat of imminent extinction. This was conservation science at its best.

Not so. It might have been a success, it might even have been the best possible science. But it was not good science.

Why It Shouldn't Work

Let us look at the different components of the black robin story in the light of modern conservation theory. There are some important theoretical cornerstones to be found in the new conservation textbooks. Proper application of those principles should have squashed the black robin programme flat.

First, genetics. Small numbers of black robins mean large amounts of inbreeding. Inbreeding reduces genetic diversity, allows the expression of lethal recessives due to homozygosity, and decreases the ability of a population to cope with adversity. Genetics predicts that a population based on one female has little chance of long-term survival.

Second, competition. Ecological theory predicts that if the niche requirements of two species overlap too much, they will be unable to coexist and competition will drive one to extinction. The problem was pied tits on Mangere Island, which forage in similar ways to black robins and are also closely related. Although the two species had coexisted in the past, this did not mean that a small number of robins in a new home would compete successfully against a thriving tit population. Caution dictated that the tits be eliminated, even though no experiment was conducted to see if competition between the species occurs.

Third, behaviour. The notion of "imprinting" was first formulated by German zoologist Konrad Lorenz earlier this century. He demonstrated that young animals imprint on the first parental object that they encounter (i.e., something reasonably large and protective). It's a smart idea because such an object is likely to be one's parent. Unfortunately, this means that robins fostered to warblers or tits are likely to be extremely confused about just what they are, and more importantly, who they should mate with. What happened? A few fostered robins were confused and two attempted to mate with tits. So not only was there a known theoretical problem, but some fostered robins demonstrated that there was also a problem in reality.

Fourth, minimum viable population size (MVP) and the 50/500 rule. The MVP for a population is the number required to ensure the survival of that population for some stated time interval. For vertebrates, most authors regard 500 as the minimum, with 50 being regarded as the minimum number required to maintain genetic variability. There is a second part to the theory which states that the effective population size (i.e., the number of breeders that actually contribute to the next generation) will be much less than the 250 pairs supposedly provided by the minimum of 500.

A short divergence into real data will help to elucidate the theory. In a study on birds of the California Channel Islands, only populations of more than 100 pairs had more than a 90% chance of surviving for 80 years; in a study of Drosophila, only 4% of the breeding population actually contributed genes to the next generation. These numbers make a joke of the black robin programme.

Enough of theory. Has someone made a dreadful mistake here? Are black robins really in an inevitable extinction vortex which has been only slightly perturbed by the best efforts of Don Merton and his many helpers? Perhaps black robins prove the theories wrong?

What Went Right

In reality, Merton and his team were doing the important groundwork of the black robin programme before the first conservation textbooks were even written. However, most of these theoretical arguments were available at the time. Inbreeding had long been identified as bad; the original formulation of competition theory was published in the 1950s, and Lorenz's notion of imprinting had been available since the 1930s. Only the 50/500 rule was still in development. The Wildlife Service was well aware that the black robin programme was in conflict with the guidelines provided by theory, even if that theory had not yet been given a coherent conservation perspective.

Options were limited, but the Wildlife Service certainly approached the problem scientifically. Doug Flack was employed to do a long-term study of breeding biology on the closest relative of the black robin, the New Zealand robin. Experiments of a sort were performed: only small numbers of black robins were available to be transferred between islands, so Flack transferred small numbers of mainland robins between islands. The two transfers were successful, both in the short term (some robins survived) and the long term (they bred and the populations increased in number). The first eggs given to warblers and tits on the Chathams were fakes. Only small numbers of real eggs were transferred into warbler and tit nests initially. All the manipulated nests were observed carefully.

Although this seems like a solid scientific approach, these were not proper experiments. They had no controls (e.g., transfer of warbler eggs between nests), and the sample sizes were too small for statistical testing (only two transfers of South Island robins between islands were undertaken). In reality, Merton and colleagues approached the problem as "firefighters" (Merton's word) rather than as scientists -- there was no time for the niceties of experimental investigation.

Even if the transfers of mainland robins to new islands had failed, the black robins would still have been moved to Mangere Island because the habitat on Little Mangere was severely degraded. The transfers of New Zealand robins and the other preliminary tests are best called exploratory science, or pilot experiments. They did not allow for proper conclusions to be drawn about the probability of a black robin transfer succeeding, or the frequency with which other species would accept robin eggs. On the other hand, their success must have provided a massive boost of confidence for Merton and crew, who had few options. At least they offered the suggestion that the proposed manipulation would succeed.

What of the imprinting problem? The notion of imprinting was a well-known phenomenon in ducks, geese and chickens, but nobody knew if the problem would arise in robins. Proper experiments, presumably with New Zealand robins, would have involved transfers of eggs or chicks to warbler or tit nests, presumably some kind of control, and a massive expenditure of resources in such things as finding and monitoring many nests and moving chicks. Had he done those experiments, Merton would presumably have found that tits, but not warblers, could raise robins, and robins would imprint on tits. Would these results have prevented the cross fostering of black robins to tits?

My feeling is probably not. Merton approached the black robin study by dealing with one problem at a time, and he is most likely to have concluded that a live, tit-imprinted black robin was of more value than no black robin at all. No theory was available, but it might be possible to deal with the imprinting problem later (which is precisely what happened; the imaginative solutions to this problem are well documented in the black robin books). Thus the experiments, although of considerable scientific merit, might have had little influence on the final outcome.

Is there competition between robins and tits? Data gathered by Flack indicated some overlap in foraging behaviour, justifying the concern. It appears, however, that although both robins and tits obtain most food from the ground, there are distinct "robin" and "tit" foraging styles, with tits spending more time off the ground, moving at faster rates, and using somewhat different feeding methods than robins. In fact, the species now cohabit successfully on both Rangatira and Mangere Islands, There may not be much competition between the species.

So far, I seem to have argued for two conclusions. First, theory has little to contribute to the doing of conservation; and second, the black robin story seems in conflict with the theory that is currently available.

Theory Still Developing

The second statement may well be at least partially true. The first is absolutely wrong.

Everything that Merton and Flack did was based in some sense or another on theory. Much of that theory was untested, or perhaps even unformulated. But the idea that "we may be able to deal with the imprinting problem later" is a theory, eminently testable when reformulated as a hypothesis, and in this case at least, it was right. Another theory suggested "this electronically heated thermos flask will serve to protect a robin's egg and keep it warm during transfer to another island". Again, a testable hypothesis, and one that proved correct.

These examples are rather specific, the second even trivially so. But they demonstrate the principle that most of the decisions that we make are theory driven, and many of the conclusions that we draw are based on experiment (frequently called "trial and error" in real life). Experiments without true controls or with small sample sizes may be poor science, but they can still contribute valuable information, and they are still science,

Theory in conservation biology is still under development, and much of it is untested. The black robin may well be an example that contradicts theory about inbreeding, or the 50/500 rule (more time needs to pass before these conclusions are drawn). But that contradiction does not prove the theory wrong. Many more tests would need to be conducted before the theory itself was rejected, which is why the definition of science includes the notion of induction.

In contrast to physics, where things tend to be fairly precise, theory in biology only provides general guidelines about the way things ought to happen. These guidelines amount to probabilistic rules, which should be adhered to, all other things being equal. The black robins were in crisis. All other things were not equal, and there was an onus on the protagonists to do the best possible job within severe constraints. Thus, Merton and Flack did the best experiments that they could among a limited array of options constrained by resources (the robin programmes were run on shoestring budgets), and time (black robins had very few years left).

Risk Paid Off

Conservation must involve the best possible science. Gut feelings, badly designed experiments, or dependence on luck rather than theory must not replace proper scientific method just because there is a crisis. Compromise of scientific principles, including rejection or bypassing of theory, is entirely acceptable after a full assessment of all available options, but carries a high risk factor, The black robin story is an extraordinary example of the right decisions being made i) in the absence of essential data, ii) despite at least some predictions of theory, and iii) with minimal potential for proper experimental exploration of options.

We were right to reward Merton for his vision and dedication (his awards include a QSM, a Doctorate of Science, and two distinguished service medals), and we are justifiably proud of our flagship species (there are now 155 black robins). But let's be realistic -- we may have been lucky that time.

lan G. McLean is a lecturer in the University of Canterbury's Department of Zoology.