The Ecological Roles of Birds

Birds provide numerous invaluable ecological services, and one of the most important is by scattering plant seeds. Seed dispersal enables plants to migrate into new territory and reduces competition with others of their own species, thereby increasing survival rates. In fact, if you enjoy spicy foods, you owe some appreciation to birds, who played a pivotal role in the evolution of chili peppers. In an example of evolutionary partnership, chili plants evolved in a way that offers birds a nutritious food source, while the plants benefited from the wide distribution of their seeds after passing through the birds’ digestive systems. Capsaicin is the molecule in spicy peppers that creates the sensation of heat we feel when it binds to pain receptors in the mouth. On a human tongue, a solution of just ten parts per million creates a distinct sense of burning, but nerve receptors in birds do not register the heat of capsaicin even if they ingest as much as twenty thousand parts per million.

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Bird digestive systems also do the seeds of the chili pepper no harm, because many birds with a fondness for them have a rather short, straight digestive pipe through which food transits quickly. Researchers have even found snails that had been eaten by a bird, passed through its digestive tract, cast out the other end, and were still alive. Moreover, chili peppers can be plucked readily from the stem only when they are ripe, which means only those seeds ready to germinate (begin growing from a seed into a plant) are swallowed by the bird. Catching the eye of birds helps pepper plants expand their range. If mammals ate chilies, they would digest and destroy them or deposit them fairly close to the plant. Birds, however, drop the undigested seeds in faraway places. The cradle of chili pepper civilization is in Brazil, in a lowland region dubbed“the nuclear area” because it has the largest number of wild varieties of chilies in the world. It is believed that the first wild chili peppers sprang to life here and were spread across much of the Western Hemisphere by birds.

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Birds shape the plant world in myriad other fascinating ways. Some two thousand species inadvertently play the middleman in sexual relations between plants. White-winged doves that survive in the desert on cactus flower nectar carry pollen between saguaro cactus flowers, and hummingbirds seek out the nectar of a variety of wildflowers and domestic crops; some hummingbirds visit thousands of flowers in a day, and as they search for nectar, they carry millions of tiny grains of pollen stuck to their heads, beaks, and feathers, brushing flowers like flying paintbrushes.

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There are places where birds and the pivotal roles they play have vanished. The extinction of the dodo, the three-foot-tall flightless bird of Mauritius, could well be the cause of the decline of the tambalacoque tree, also known as the dodo tree, which is highly valued for its timber (wood). Some plants have just a single animal partner that plays a key role in its life, and in the case of the peach- tree-like tambalacoque, the dodo’s digestive tract may have been vital in paving the way for the tree’s successful growth. As the seeds moved through the bird’s system, fruit pulp was scrubbed of, reducing the risk that bacteria and fungi would kill the seeds before they germinated. These days, botanists growing tambalacoque trees pass their seeds through wild turkeys or even gem-polishing machines to roughen and clean them in preparation for planting.

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Large enough flocks of birds can also be a factor in the weather. When millions of migratory seabirds arrive in the Arctic each summer,they bring a huge burst of guano (bird waste). As bacteria go to work on the guano and break it down, they emit ammonia. As sulfuric acid and water combine with the ammonia in the atmosphere, bigger particles are formed, which become the nuclei for cloud droplets and thus create cooling clouds. The number of cloud droplets near seabird colonies can be 50 percent more than in those areas without birds. Smaller droplets are also formed, which reflect sunlight and contribute to the cooling effect. When seabirds change their migratory patterns or disappear, experts believe they may contribute to changes in Arctic weather.

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?Birds provide numerous invaluable ecological services, and one of the most important is by scattering plant seeds. Seed dispersal enables plants to migrate into new territory and reduces competition with others of their own species, thereby increasing survival rates. In fact, if you enjoy spicy foods, you owe some appreciation to birds, who played a?pivotal?role in the evolution of chili peppers. In an example of evolutionary partnership, chili plants evolved in a way that offers birds a nutritious food source, while the plants benefited from the wide distribution of their seeds after passing through the birds’ digestive systems. Capsaicin is the molecule in spicy peppers that creates the sensation of heat we feel when it binds to pain receptors in the mouth. On a human tongue, a solution of just ten parts per million creates a distinct sense of burning, but nerve receptors in birds do not register the heat of capsaicin even if they ingest as much as twenty thousand parts per million.