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A challenge for any diving bird is the change in refraction between air and water. The eyes of many birds have two foveae (the fovea is the area of the retina with the greatest density of light receptors), [22] and a kingfisher can switch from the main central fovea to the auxiliary fovea when it enters water; a retinal streak of high receptor ...
Coot species that migrate do so at night. The American coot has been observed rarely in Britain and Ireland, while the Eurasian coot is found across Asia, Australia and parts of Africa. In southern Louisiana, the coot is referred to by the French name "poule d'eau", which translates into English as "water hen".
Nocturnal migration can be monitored using weather radar data, [40] allowing ornithologists to estimate the number of birds migrating on a given night, and the direction of the migration. [41] Future research includes the automatic detection and identification of nocturnally calling migrant birds.
The Arctic tern has the longest migration journey of any bird: it flies from its Arctic breeding grounds to the Antarctic and back again each year, a distance of at least 19,000 km (12,000 mi), giving it two summers every year. [19] Bird migration is controlled primarily by day length, signalled by hormonal changes in the bird's body. [20]
Species that live in the far north, such as the European nightjar or the common nighthawk, migrate southward with the onset of winter. Geolocators placed on European nightjars in southern England found they wintered in the south of the Democratic Republic of the Congo. [9] Other species make shorter migrations. [8]
Robertson and Loss were two of four co-authors on a study that looked at the migrations of 150 bird species along flyways from South America to the high Arctic, using remote sensing and satellite ...
Milwaukee is under "high" migration alert Wednesday night, with more than 27,000 birds expected to migrate over the city. Kakatsch said colder weather usually drives an upswing in migration in the ...
It may be mobbed by birds while there is still light, and by bats, other nightjar species or Eurasian woodcocks during the night. Owls and other predators such as red foxes will be mobbed by both male and female European nightjars. [3] Like other aerial birds, such as swifts and swallows, nightjars make a quick plunge into water to wash. [23]