Editing Bird migration (section)

===Diurnal migration in large birds using thermals===
[[File:Vulture 19o05.jpg |right |thumb |[[Griffon vulture]] soaring]]

Some large broad-winged birds rely on [[thermal]] columns of rising hot air to enable them to soar. These include many [[bird of prey|birds of prey]] such as [[vulture]]s, [[eagle]]s, and [[buzzard]]s, but also [[stork]]s. These birds migrate in the daytime. Migratory species in these groups have great difficulty crossing large bodies of water, since thermals only form over land, and these birds cannot maintain active flight for long distances. [[Mediterranean Sea|Mediterranean]] and other seas present a major obstacle to soaring birds, which must cross at the narrowest points. Massive numbers of large [[Bird of prey|raptors]] and storks pass through areas such as the [[Strait of Messina]],<ref>{{cite web |url=http://www.surfbirds.com/mb/Features/messina/messina-0302.html |title=European Birding Hot Spot: The Strait of Messina, southern Italy |last=Corso |first=Andrea}}</ref> [[Gibraltar]], [[Falsterbo]], and the [[Bosphorus]] at migration times. More common species, such as the [[European honey buzzard]] ''Pernis apivorus'', can be counted in hundreds of thousands in autumn. Other barriers, such as mountain ranges, can cause funnelling, particularly of large diurnal migrants, as in the [[Central America]]n migratory bottleneck. The [[Batumi]] bottleneck in the Caucasus is one of the heaviest migratory funnels on earth, created when hundreds of thousands of soaring birds avoid flying over the Black Sea surface and across high mountains.<ref name=Gavashelishvili11>{{cite journal |last=Maanen |first=E. van |author2=Goradze, I. |author3=Gavashelishvili, A. |author4=Goradze, R. |year=2001 |title=Opinion: Trapping and hunting of migratory raptors in western Georgia |journal=Bird Conservation International |volume=11 |issue=2 |pages=77–92 |doi=10.1017/S095927090100017X |doi-broken-date=1 November 2024 |doi-access=free}}</ref> Birds of prey such as honey buzzards which migrate using thermals lose only 10 to 20% of their weight during migration, which may explain why they forage less during migration than do smaller birds of prey with more active flight such as falcons, hawks and harriers.<ref>Gensbol, B; (1984) Collins Guide to the Birds of Prey of Britain and Europe, p.28</ref>

[[File:The natural terrace of Mount Dinnammare on the Strait of Messina, sicily .JPG|thumb|The bottleneck of the [[Strait of Messina]], point of transit of the migrations, seen from the [[Peloritani]] mountains, [[Sicily]]]]

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.<ref>{{cite journal |last=Panuccio |first=M. |author2=Martín, B. |author3=Onrubia, A. |author4=Ferrer, M.  |year=2017 |title=Long-term changes in autumn migration dates at the Strait of Gibraltar reflect population trends of soaring birds |journal=Ibis |volume=159 |pages=55–65 |doi=10.1111/ibi.12420 |issue=1 |hdl=10261/141899 |hdl-access=free}}</ref>

[[File:Rubythroathummer65.jpg|thumb|[[Ruby-throated hummingbird]]]]