Status
The Barn Swallow has an enormous range, with an estimated global extent of 51.7 million square kilometres (19.96 million square miles) and a population of 190 million individuals. Although global population trends have not been quantified, the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (that is, declining more than 30 percent in ten years or three generations). For these reasons, the species is evaluated as "least concern" on the 2007 IUCN Red List, and has no special status under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which regulates international trade in specimens of wild animals and plants.
This is a species which has greatly benefited historically from forest clearance, which has created the open habitats it prefers, and from human habitation, which have given it an abundance of safe man-made nest sites. There have been local declines due to the use of DDT in Israel in the 1950s, competition for nest sites with House Sparrows in the US in the 19th century, and an ongoing gradual decline in numbers in parts of Europe and Asia due to agricultural intensification, reducing the availability of insect food. However, there has been an increase in the population in North America during the 20th century with the greater availability of nesting sites and subsequent range expansion, including the colonisation of northern Alberta.
A specific threat to wintering birds from the European populations is the transformation by the South African government of a light aircraft runway near Durban into an international airport for the 2010 FIFA World Cup. The roughly 250 metres (275 yards) square Mount Moreland reed bed is a night roost for more than three million Barn Swallows, which represent one percent of the global population and eight percent of the European breeding population. The reed bed lies on the flight path of aircraft using the proposed La Mercy airport, and there were fears that it would be cleared because the birds could threaten aircraft safety. However, following detailed evaluation, advanced radar technology will be installed to enable planes using the airport to be warned of bird movements and, if necessary, take appropriate measures to avoid the flocks.
Climate change may affect the Barn Swallow; drought causes weight loss and slow feather regrowth, and the expansion of the Sahara will make it a more formidable obstacle for migrating European birds. Hot dry summers will reduce the availability of insect food for chicks. Conversely, warmer springs may lengthen the breeding season and result in more chicks, and the opportunity to use nest sites outside buildings in the north of the range might also lead to more offspring.
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