Some bird species typically fly only at night, occasionally spending more than 24 hours in flight to avoid the need to stop in inhospitable or unfavourable areas with insufficient access to food, such as deserts and seas. One such species is the great reed warbler (Acrocephalus arundinaceus), which is known in Latvia. During their month-long migration, these birds can fly for up to 34 hours without landing. The migration route of the great reed warbler leads from Northern Europe to the sub-Saharan region of Africa. As researchers have concluded, the birds can fly at very high altitudes (up to 6,300 m). One explanation could be that, at high altitudes, the birds avoid overheating.