The above was the original title of an essay I wrote some 15 years ago, a bit of a rant really, in response to constant needling by some people wondering why I was studying tiny nondescript little warblers for my Ph.D. research instead of something more important… you know… like tigers. After all I was doing field work in a Tiger Reserve anyway, and there aren’t any warbler reserves, so why was I wasting my time? Hence, eventually, my response, outlining the greater importance of warblers.
That essay somehow landed on the desk of Joanna Van Gruisen, who happened to be editing a coffee-table book on wildlife conservation in India for the Ranthambore Foudation. She liked my contrarian essay well enough to want to include it in the book “In Danger” where most of the other contributions were about much more charismatic megafauna, including tigers! She did tone down the title, turning it into a question – see below. In the years since, I keep hearing from various people in India that they have read that article, which was also reprinted in a magazine, and more recently in another edited book on ornithological writings from India. Sometimes I get the sense that more people have read this article than have read any (or all) of my academic papers. It is this kind of unexpected (honestly) response which encouraged me to try more science writing for nonscientists, eventually leading to this blog and other writing I am doing currently.
This warblers vs. tigers polemic, though, keeps coming back. Recently, a newfound friend on the internets, Arati Rao, wrote to me about going back to re-read it, wishing she could own a copy, but that the original book is now out-of-print. At her behest, therefore, I am reproducing the article below, and hope it finds new readers. I think I will scan the original print version also and post it online soon. Meanwhile, here it is, below the fold:
Are Warblers Less Important Than Tigers?
Are Warblers less important than Tigers?
Now what kind of a stupid question is that?! Everyone knows that tigers are more important, being large predators, as apex species, at the top of the food chain, flagship species for conservation… etc. … etc. … etc.!!
These are arguments I have to face often enough when I tell people I am studying warblers—in Kalakad-Mundanthurai Tiger Reserve! For some reason, studying these tiny, nondescript, common birds is thought to be an entirely trivial, indeed arcane, academic pursuit of little practical or conservation value.
“What can studying little birds tell me about the habitat of large mammals, which are my primary concern?”—asks the reserve manager. On the other hand, if we focus on the larger mammals—the apex species philosophy of Project Tiger—and do our best to improve their habitat, other species will also naturally benefit. Given limited funds and manpower for conservation (research and action), is it not better to focus on the mega-fauna and let the mini- and micro-fauna take care of itself? The only small creatures one should worry about then are those that may form part of the food chain leading up to the larger focal species.
Before you accuse me of a biased perspective (which is undoubtedly true, for I make my living watching little warblers!), let me state that, in defending these little creatures, I am also arguing in favor of a broader ecological perspective in conservation—one that goes beyond the charismatic mega-fauna, and starts looking at species more in terms of their ecological role in the system, rather than their appearance/charisma, or tourism potential!
So what is the ecological role of my favoured little leaf-warblers?
Leaf warblers (Genus Phylloscopus) must surely rank among the least glamorous vertebrates, so utterly lacking in charisma that even many die-hard bird watchers dismiss them lightly, scarcely bothering to try and even identify them to species level. Part of the problem is, of course, the fact that they are all small, dull-green coloured, and highly active in the forest canopy, making identification in the field difficult. It is only rarely—either when one is truly nuts about birds or when the fate of one’s Ph.D. thesis hangs on such identification—that one develops the eye for the subtle morphological, auditory and behavioural differences between species. These difficulties in identifying species, however, need not bother our busy manager too much, since they (the leaf-warblers) are all pretty similar ecologically as well—the role they play in the forest is largely independent of their taxonomic status, except insofar as structural aspects of their foraging microhabitat within the forest canopy are concerned.
All 18 species leaf warblers occurring in the Indian subcontinent are migratory, breeding in the temperate summers from Himalaya north to the Arctic circle, and taking over the peninsular (including Himalayan foothills, and much of Northeast India) forests from September through May. While each individual may weigh only 7-11 grams (range includes all species; give or take a gram), one may still emphasize the term take-over, when describing their relationship to their forest habitats: they number in the billions and form probably the most abundant avian guild in the subcontinental forests during our tropical winter. My study at Mundanthurai (in the southern western ghats) records a density of 6-8 leaf warblers (of two species) per hectare of forest—usually any given patch of forest may have 2-3 species, depending on the type of forest; and I doubt there is any forest habitat in India that does not host at least one species some time of year. Picking a random hectare from my 20 ha study plot at Mundanthurai, I find 6 leaf warblers (of 2 species) making it their home for 7-8 months— for these are territorial individuals that remain on site for much of the winter. And what do they do during this period? Well, eat insects, mostly! Humdrum as their lives may sound, they spend over 75% of their waking hours foraging for insects (and other arthropods—but insects predominate) in the foliage. Since they are not concerned about finding mates or raising young during this season, and want merely to survive in good shape for the next summer, their other activities—preening and maintaining territories through vocal and visual dialogue with neighbors—does not take much time. Hmm… a bunch of small, dull birds spending most of their day peering at leaves in search of insects—do I seem to be only weakening the defense? Not really…
Consider the fact that each leaf-warbler, on average, eats 3 insects every waking minute (this is averaging over all their activities throughout the day). Since they forage by picking prey off a substrate—mostly leaf, sometimes also twigs and flowers—the prey largely consists of herbivorous insects. In the case of my one hectare on Mundanthurai, it is mostly caterpillars eating leaves. A single leaf-warbler thus eats an average of 180 insects every hour, or about 1980 per day (assuming an average 11 hour working-day from dawn to dusk). The six individuals on our plot thus rid the plants of almost 12,000 insect pests—every day!! Multiply that with the number of days (200-250) that they are in residence on that one ha plot and you may begin to appreciate the service they render to all the plants. Now I ask you to consider removing these warblers from the study plot, since they seem to take away so much research and conservation energy from your more favoured mammals, and picture the forest as it may appear in a few weeks’ time…! The scenario could become even more dramatic if you (in your large-mammal chauvinism) remove all the other insectivorous birds from the plot as well: I estimate each hectare of Mundanthurai’s forest has at least 40 insectivorous birds, including other warblers and flycatchers (both resident and migrant), minivets, shrikes, drongos, babblers etc. The average number of prey may come down to just over 2 per bird per minute—which gives a total of about 5000 insects per hour, or 55,000 per day in every hectare of forest! Remove those insectivores: …and don’t be surprised if in a few weeks your plants start to appear ragged with their foliage tattered… and your endangered langurs become unhappy because so many leaves are now packed with toxic anti-herbivore compounds produced in response to caterpillar nibblings… and the plants make fewer flowers and fruits as they are forced to spend too much energy in self defense… in turn making the nectarivores and frugivores unhappy… and regeneration of the forest slows down as fewer seeds get produced and dispersed… and the ground starts to dry faster because the canopy is thinner and more sunlight gets in… I leave you to work out the rest of the ecological cascade effects on your own!! For now, I’d be happy if you simply pause to appreciate the job done by the nondescript little green jobs—the leaf warblers—and their insectivore colleagues that travel thousands of kilometers every year to eat all those insects.
Before you start protesting that you will never contemplate removing all those birds, and that I am just another doomsayer, consider the fact that 80% of the warblers (esp. the Green leaf warbler, which is the most common one here) as well as the next most abundant migrant (Blyth’s reed warbler) spending each winter at Mundanthurai come from the forests of the hill regions around the Caspian Sea, from Turkey east through Kashmir, including bits of southern Russia and Afghanistan. Now imagine that these hills—breeding grounds for so many migrant insectivores—are deforested on a large scale, either directly by us or through effects of global climate change, cutting down the bird population by 90%. Such declines is not very unrealistic, as those studying migrant forest birds in the Americas will tell you—though they worry more about forests in the wintering areas being cut down rather than in the breeding grounds. In fact, over the past two decades, Americans and Europeans are increasingly facing the prospect of another Silent Spring. Not, this time, due to the factors mentioned in Rachel Carson’s clarion call in the 1960s—over-use of chemicals in agriculture at the height of the green revolutions—but to a suite of other human activities that have hit the habitat of avian migrants in both their northern breeding grounds and southern wintering grounds. Many species of migrant songbirds, which enliven the northern spring after the dreary and silent winters, have been pushed to the brink of extinction—some like the Kirtland’s warbler down to a few scores of breeding pairs—over the past two decades, even as my ornithologist comrades in the west are racing against time to figure out the causes of these declines, so we may try and reverse the process! The culprits are, of course, us humans: deforesting the tropical wintering grounds; fragmenting the temperate forests into suburban woodlots more accessible to human subsidized nest-predators such as domestic cats and other small carnivores (wild or feral) thriving on our garbage; and directly subsidizing populations of non-migratory nest-parasites like the north-American cowbird through back-yard bird feeders, enabling them to survive the harsh winter, and fool over 200 gullible species of songbirds into raising their offspring! We seem to be particularly adept at causing damage to the ecological fabric of this planet, even when we mean good—feed them poor little birdies in the winter, or the cute raccoons at night!!
Getting back to our continent, where we have no information on population trends of forest birds at all—whether resident or migratory, in tropical south and south-east Asia or temperate Russia, Mongolia and Siberia—declines paralleling those on the other continents are very much on the cards, if, indeed, they haven’t occurred already! Given the contempt that these migrants have for human geopolitical boundaries, their populations are subject to forces beyond the control of any one national conservation agency, let alone the manager of a single Tiger Reserve. And if their populations are found to be declining as drastically as many New World migrants’ have over the past several decades, mammal chauvinists may be reduced to haplessly watching the habitats of their favourite creatures getting degraded.
Do you think even the tigers might get worried about such a scenario??
Is it worth studying these warblers, trying to figure out what makes their populations tick, and how to save them—and ensure they continue to keep all those insects down?
Are warblers less important than tigers?? Isn’t the question itself meaningless?