<P> From observing the migration of eleven soaring bird species over the Strait of Gibraltar, species which did not advance their autumn migration dates were those with declining breeding populations in Europe . </P> <P> Many of the smaller insectivorous birds including the warblers, hummingbirds and flycatchers migrate large distances, usually at night . They land in the morning and may feed for a few days before resuming their migration . The birds are referred to as passage migrants in the regions where they occur for short durations between the origin and destination . </P> <P> Nocturnal migrants minimize predation, avoid overheating, and can feed during the day . One cost of nocturnal migration is the loss of sleep . Migrants may be able to alter their quality of sleep to compensate for the loss . </P> <P> Many long - distance migrants appear to be genetically programmed to respond to changing day length . Species that move short distances, however, may not need such a timing mechanism, instead moving in response to local weather conditions . Thus mountain and moorland breeders, such as wallcreeper Tichodroma muraria and white - throated dipper Cinclus cinclus, may move only altitudinally to escape the cold higher ground . Other species such as merlin Falco columbarius and Eurasian skylark Alauda arvensis move further, to the coast or towards the south . Species like the chaffinch are much less migratory in Britain than those of continental Europe, mostly not moving more than 5 km in their lives . </P>

Write a short note on migration of birds