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THE MIXED-SPECIES FLOCKS OF MANU THE MAXIMUM BIRDING EXPERIENCE IN THE WORLD

In most forested areas of the planet, whether temperate latitudes or in the tropics, insect-eating birds often form flocks of several species. These flocks are familiar to every birdwatcher in Europe and North America, for instance, and are composed of chickadees (which are called "tits" in Europe) with some small woodpeckers and other insect-eating species.

In temperate latitudes, these flocks are largely confined to the nonbreeding season, which is to say, from the fall through the winter.

In the tropical rainforests of the world, mixed-species flocks of insect-eating birds exist all year round, in breeding season and outside the breeding season. In all the world, the mixed-species flocks of the Amazon rainforest are the most complex known, and of the Amazonian flocks, those of SE Peru, particularly in the Manu and Tambopata areas, appear to be not only the most complex bird flocks in the world, but also the most complex multi-species assemblages of any group of organisms on Earth.

In Manu, research that I carried out between 1976 and 1983 showed that mixed species flocks include 103 species of forest birds, including virtually every species that actively searches foliage for insects. I also found that up to 70 species of birds can be found in one mega-flock at the same time. These mega-flocks are found normally only from about 1100 am until 230 pm in tall, lowland forest, and they are result of the joining together of a permanent understory flock, an entirely separate and permanent canopy flock, and a temporary flock of fruit-eating tanagers.

These midday megaflocks are the birder's equivalent of a "moon shot"---the most extreme birdwatching on the planet.

If you follow one of these megaflocks for a few hours during midday, you should see rarer flock species join and leave the flock, tthus bringing your flock list to 100 species! This suggests that, despite the conventional wisdom that early morning birding is best, in fact the best tropical birding experience in the world is during the midday hours. To enjoy these large flocks, we might suggest that you take a mid morning nap and then go out at 1000 am or 1030 am with an excellent box lunch and follow mega-flocks during the midday hours to maximize your flock watching experience  

During my doctoral research on mixed-species flocks of Manu, I discovered that three species of birds (the Bluish-slate Antshrike, the White-winged Shrike-Tanager, and the Black-fronted Nunbird) were "sentinels", who made a living by giving early warnings of attacking hawks, and so endeared themselves to the more actively-foraging flock species, which then followed them all day through the forest. But these sentinels extracted payment for their sentinel services---by catching insects flushed into the air column by the more actively foraging birds. And when a particularly juicy grasshopper or other escaping, flying insect was flushed into the open, these specialized sentinels sometimes resorted to lying to get a leg up in the aerial competition to catch the fleeing insect. They cried "hawk" when there was no hawk, presumably to slow up other birds that were considering going after the flushed insect. This behavior, which is like the trick of the boy who cried wolf, appeared surprisingly frequently, and was the subject of a short article that I published in the scientific journal "Nature" in 1986----the article was entitled, "Birds that "cry 'Wolf!'".

To enjoy mixed-species flocks in Manu, ask your favorite travel agent or tour operator to check carefully with ground operators to ensure that you get an expert birding guide, as only a select few guides (probably less than 6 or 8 in all of Peru) really understand and can identify the many, many species of these mixed species flocks.

Charles A. Munn, Ph.D., Chairman of the Board, Tropical Nature (a nonprofit nature conservation group---www.tropicalnature.org)