Reverse migration (birds)

Keith Vinicombe suggested[2] that birds from east of Lake Baikal in Siberia (circled) could not occur in western Europe because their migration routes were too north–south.

[3] Many birds that detour from their regular migration patterns find themselves in adverse wintering circumstances, so a considerable number may not survive.

However, in most small species, such as passerines, the route is genetically programmed, and young birds navigate innately to their wintering area.

[3] Genetic variations may be triggered by a range of factors, including mutations in the genes responsible for the sensing of environmental cues such as photoperiod (day length) or geomagnetic fields, which birds use for navigation.

Manual monitoring radar data not only enhances our understanding of bird behavior, but it also plays an important role in avian conservation efforts and the protection of critical stopover sites along migration routes.

[5] A miniature transmitter is attached to the subject animal and emits a very high frequency signal (30–300 MHz) that can be picked up by one or more receivers.

[6] The combination of small transmitters and triangulation via many receivers has transformed the area of avian studies, allowing scientists to unearth minute data about bird behavior, navigation, and habitat utilization.

This data is essential for conservation efforts, as it helps identify stopover locations and key habitats that are crucial for the survival of migratory birds.

[8][4][9][7] Thrushes migrating southwards were radio-tracked to examine when and why some individuals, during a stopover along the northern coast of Mexico, would not continue south but fly inland northerly.

It has been observed that birds increase their hematocrit before consuming large amounts of food for fat stores, which could explain why these birds chose to travel 200 km in reverse to access high-quality softshell prey to supply fat and increase their hematocrit before long migrations.

When broad-winged hawks traveling north reach the tip of the Door Peninsula and the islands beyond, the long stretches of water sometimes unnerve them.