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They get through around an astronomical 500 million tons of flies, bugs and creepy-crawlies every year. Such are their ravenous cravings, the combined feasting of the known 6,000 species of
insectivorous birds weighs heavier than all the fish and meat consumed by humanity. More importantly, catching and swallowing potentially harmful plant-eating pests is a vital service
provided by birds for safeguarding trees. Scientists say the bulk of the insectivorous food is caught by forest birds, with as much as 300 million tons of prey consumed annually. Besides
revealing the prey mass of birds, zoologists at the University of Basel, the University of Utah (Salt Lake City), the University of Illinois (Chicago), and Koç University (Istanbul) have
been able to calculate what the figures mean in energy consumption terms. In short, it equates to 2.8 exajoules, or the amount of energy used by a megacity such as New York. Conservationists
will be quick to emphasise the importance of preserving bird numbers to protect woolands, particularly in an age when so many migratory species such as wood and willow warblers, pied
flycatcher and tree pipits are in decline. One illustration put forward regularly by ecologists to show how birds eat vast amounts of invertebrates is through the nesting strategy of blue
tits. A single breeding pair, with a clutch of up to 10 fledglings, have to catch around 10,000 small green caterpillars by the time the youngsters are ready to leave the nest. Dr Martin
Nyffeler from the University of Basel, who led the study published in the journal, Science of Nature, explains why birds feeding billions of herbivorous insects, including potentially
damaging caterpillars and beetles, to nestlings is vital. He said: “In doing so, birds – in concert with other natural enemies such as spiders and ants – contribute to natural insect pest
suppression resulting in reduced herbivore damage." A previous study by Dr Nyffeler calculated how spiders are consuming even more insects than birds. With an estimated 45,000 species
worldwide and population densities of up to 1,000 per square metre, researchers worked out arachnids wiped out an estimated 400-800 million tons of prey every year. To put this in context,
the Food and Agriculture Organisation of the United Nations (FAO) says humans eat about 400 million tons of meat and fish annually. At the Royal Society for the Protection of Birds, the new
study is seen as evidence of how insects play their part, good and bad, in the balance of nature. An RSPB spokeswoman said: “Insects are an important and fascinating part of the wildlife in
our gardens and should be welcomed to our outdoor spaces. “They can be an important source of food for other animals, like birds and bats, essential to pollinate our flowering plants and
crops, predators to other insects like aphids, and useful workers when it comes to decomposition and giving us nutrient rich soil. “We can attract them in a variety of ways, from simply
planting insect-friendly plants and flowers, to building habitats for them to live. "The RSPB’s website has lots of ideas on how you can give nature a home.”