Migration of soaring birds in the Strait of Gibraltar

Across Europe, up to 38 species of diurnal raptors can be found, and almost all undertake migratory journeys across parts of their European range. Some of these migrations are short, but many involve thousands of kilometers, demanding immense energy and testing the survival of these birds.

To reduce energy expenditure, large-winged raptors migrate during daylight using soaring and gliding, taking advantage of thermal currents created when the sun heats the land. These thermals do not form over water, which strongly influences the migration routes of raptors and other soaring birds, including storks.

This makes certain locations in Europe critical for bird migration observation. The Strait of Gibraltar, in the western Mediterranean, is one of the most important corridors, where Europe and Africa are only 14 kilometers apart. Every year, thousands of raptors and storks pass through this narrow passage, making it a key site for raptor migration Strait of Gibraltar, soaring bird migration Europe, and birdwatching in the Strait of Gibraltar.

In the eastern Mediterranean, similar concentrations of soaring birds occur in Turkey and Israel, but the Strait of Gibraltar remains the most significant western migration hotspot in Europe. For anyone studying or observing bird migration in Europe, this strait is an essential site due to the high density of migrating raptors and storks.

The Strait of Gibraltar serves as a vital corridor for migrating birds, where 28 raptor species and 2 stork species can be regularly observed. Each year, an estimated 300,000 raptors and 150,000 storks traverse this narrow passage during their spring and autumn migrations. This region concentrates the bulk of western Europe’s soaring birds, making it one of the most important migration hotspots in the world. Notably, species such as the Black Kite, Egyptian Vulture, Booted Eagle, and Short-toed Snake Eagle reach their highest recorded migration numbers globally here.

Bird migration in the Strait of Gibraltar occurs throughout the year, but the peak periods for soaring birds are February to May and July to November. Here is a detailed month-by-month overview:

• January: Migration is limited. Only White Storks and the first Black Kites are regularly observed.
• February: Migration intensity increases. Black Kites, White Storks, Black Storks, Egyptian Vultures, Red Kites, Griffon Vultures, Short-toed Snake Eagles, Marsh Harriers, Sparrowhawks, Common Buzzards, Ospreys, and Common and Lesser Kestrels start crossing the Strait in significant numbers.
• March: One of the best months for spring raptor migration in the Strait of Gibraltar. Most of the above species reach their peak migration.
• April: Migration continues in good numbers. The Hobby and Honey Buzzard appear, with the Honey Buzzard increasing toward the end of the month.
• May: Most populations have crossed, but smaller numbers continue. The Honey Buzzard migration reaches its mass movement in the first half of May, while Griffon Vultures also peak.
• June: Migration slows dramatically. Few birds cross regularly, with Griffon Vultures being the most common raptor.
• July: The postbreeding migration begins. Black Kites and White Storks are the first pioneers, with thousands crossing on some days.
• August: Black Kites and White Storks reach their peak migration. Sparrowhawks, Egyptian Vultures, Common and Lesser Kestrels, Montagu’s Harriers (peaking late August), and Marsh Harriers also join. The Honey Buzzard migration is remarkable, with thousands crossing from late August to early September.
• September: This is the month with the highest diversity of soaring birds. Many species reach their peak, including Black Storks, Egyptian Vultures, Short-toed Snake Eagles, Booted Eagles, Marsh Harriers, Ospreys and Lesser Kestrels.
• October: Migration continues at lower numbers. The Hobby and Common Buzzard reach their maximum passage. The Griffon Vultures are starting to cross in large numbers.
• November: Most species cross sporadically. Griffon Vultures reach peak migration, while White Storks begin their prebreeding migration back to Europe.
• December: Migration is minimal. The main movements involve White Storks returning north.

The wind in the Strait of Gibraltar plays a crucial role in shaping soaring bird migration. Wind conditions can significantly affect the routes, timing, and concentration of migrating birds.

When winds blow laterally with moderate intensity, they can alter the trajectory of birds. This is particularly important for birdwatchers and researchers choosing observatory points:

• Easterly winds tend to concentrate birds along the western side of the Strait.

• Westerly winds shift the migration flow toward the eastern side.

During strong winds, many birds avoid crossing the Strait, waiting for more favorable conditions. After several days of persistent strong winds, the subsequent decline in wind often results in impressive concentrations of soaring birds crossing the Strait.

These periods also highlight the presence of large numbers of raptors and storks resting on land, waiting for optimal migration conditions. Understanding wind patterns is therefore essential for anyone studying or observing bird migration in the Strait of Gibraltar.

In addition to the common migrating species, the Strait of Gibraltar is home to several rare raptor species in Spain. These birds are observed almost every year, with some appearing regularly. Notable rare species include the Rüppell’s Vulture, Greater Spotted Eagle, Lesser Spotted Eagle, Pallid Harrier, and Long-legged Buzzard.

The presence of these scarce raptors makes the Strait of Gibraltar an exceptional destination for birdwatching and soaring bird migration enthusiasts. Witnessing these rare species during migration is a unique experience and adds another compelling reason to visit this renowned migration corridor.