Barn Swallows
nest in Europe, Asia, and Africa as well as America. Originally, they
nested in caves, hollowed-out crevices beneath tree roots on cliffs and
banks, and places like that. These nesting spots were rare and tricky
to find, so there weren't very many Barn Swallows. But when people started
building structures, swallows immediately started taking advantage of
them. Swallows don't compete with humans for food, and humans quickly
noticed that swallows eat mosquitoes and other flying insects, so people
liked sharing their homes with them. Some cultures even believe that swallows
nesting on a house bring good luck. As humans spread to more and more
places and built larger and larger settlements, swallows increased right
along with them. This is because no matter where swallows lived, there
was abundant food for them--flying insects can be anywhere!
In some arid
places swallows did not increase when people started building, but are
now increasing, thanks to irrigation. How did this change things? By watering
fields, farmers made mud available! After all, swallows need both a place
to build their nest AND building materials!
When the
first European ornithologists came to America, they were already familiar
with Barn Swallows. On this continent they found swallows nesting on Native
American buildings and structures. As more and more people settled here,
building more and more places where swallows could nest, the swallow population
increased.
Nowadays
nesting structures are easy for swallows to find. They have more trouble
finding flying insects now that people use pesticides. But as long as
there are mosquitoes, houses, and barns, there will be Barn Swallows.