New research has shown that there are approximately 50 billion birds in the world — six per person. They belong to 9,700 species. Scientists noted that they have described only 92% of birds — the remaining 8% are so rare that they are difficult to record.
The results of the study were published in the journal Proceedings of the National Academy of Sciences. A team of scientists from the University of New South Wales in Australia has calculated the approximate number of birds in the world. The group combined data from a billion observations stored in the eBird online database. The researchers then developed an algorithm to estimate the population of each species.
The calculations took into account the “detectability” of each species — the probability that a person would spot a bird and publish the results of their observations in eBird. Other characteristics included size and color, whether the birds fly in flocks, and how close they live to cities.
The results showed that there are approximately 50 billion birds belonging to 9,700 species living in the world. The most common are house sparrows (1.6 billion individuals), common starlings (1.3 billion individuals), Delaware gulls (1.2 billion individuals), and barn swallows (1.1 billion individuals).
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At the same time, about 12% of species are estimated to include fewer than 5,000 individuals. And there are species that number only 100 individuals, such as the black-breasted three-toed woodpecker. The scientists added that 8% of species were not included in the study because there are too few birds belonging to them and the authors did not have available data on them.
“We will be able to say how these species are doing by repeating the study in five or ten years. If their numbers continue to decline steadily, we will take this as a warning sign,” said Associate Professor Will Cornwell, co-author of the study. Estimating species numbers is an important step in animal conservation, ecologists added. By counting them correctly, we can find out which species are vulnerable and how populations change over time.
Biologists have tracked the emergence of a new species of bird
Both DNA sequencing and physical analysis confirmed the emergence of a new species of Darwin’s finches, unique inhabitants of the Galapagos Islands. Darwin himself suggested that all of them — and there are almost 20 species of these finches — descended from a single ancestor, whose descendants adapted to different conditions, feeding habits, and breeding patterns. A pair of such species apparently interbred recently, leading to the emergence of a third species through hybrid speciation.
It all started when, during an expedition to Daphne Island, biologists Peter and Rosemary Grant from Princeton University noticed a large cactus ground finch, Geospiza conirostris, which had not been seen there before.
These finches are noticeably larger and sing differently than the three species native to Daphne. “We didn’t see it fly across the sea, but we noticed it shortly after its arrival,” says Peter Grant. “It was so different from the other birds that we knew it had not hatched on Daphne Island.”
However, this male then mated with two females of the local medium ground finch Geospiza fortis, and they produced offspring. In principle, this is rare in nature, but even rarer is the ability of hybrids to mate with each other and reproduce. The new line of finches succeeded in doing so. Soon, biologists observed a new species with a whole set of necessary characteristics, from the size and shape of the beak to the sound of the song and the manner of attracting a mate.
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