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Image: Tommy Hansen

Ever since Alfred Hitchcock’s thriller The Birds, watching birds flock has never been the same. The following pictures, however, leave that association behind and instead show the remarkable skill and coordination that flying in a flock requires.

Flocking is a collective animal behaviour that can be observed in birds, fish and insects; all animals in fact, only that for some species, it is called herding, swarming, schooling or, er, summer sale.

2. Thousands of grackles swarm around Houston’s Wortham Center at dusk:

Image: Adam Baker

It is an instinctive behaviour that follows simple rules and does not require central coordination, but whose results can be astounding: bird migrations over thousands of miles, for example, or complex structures like termite mounds. The advantages of a flock versus a single animal are that a group of animals is stronger, better protected and can hunt or feed better.

In birds, flocking behaviour can be observed beautifully in flight when often huge flocks of birds cover an area in the sky, flying around apparently without coordination but also without any collisions. Three general rules guide flocking behaviour, and, as tests have shown, not only for animals:

Separation: don’t step on your neighbour’s toes (or claws), avoid crowding;
Alignment: keep in line and steer toward the average direction of the neighbours;
Cohesion: keep the structure and steer toward the average position of the flock neighbours.

3. Following all the rules? A flock of red-winged blackbirds at Quivira National Wildlife Refuge in Kansas:

Image: Jerry Segraves

Bird formations especially have puzzled humans for a long time until studies revealed a few simple facts.

1) Each bird flapping its wings creates an uplift for the birds that follow. By flying in a “V” formation, for example, the whole flock gains a 71% greater flying range than each bird flying alone.

4. Watch out, here we come! Synchronized seagull formation:

Image: David Joyce

5. Canadian geese in classic V-formation above Lake Michigan:

Image: Kelly Martin

2) Each formation has a lead bird that rotates back into the formation when it gets tired so that another bird can take over the head position.

3) Similarly, any bird falling out of formation soon realises the extra resistance when flying alone. It quickly moves back into line to take advantage of the lifting power of the bird immediately in front of it. For that reason, geese flying at the back of a formation, for example, honk encouragingly to those in the front to keep up their speed.

6. A reinforced V, for greater encouragement or did they just feel chatty?

Image via Dehornberger

4) When a bird in formation gets too tired, sick or wounded to continue, at least one bird will drop out of formation as well and follow it for protection and help. They stay with the wounded bird until it dies or is able to fly again. If their original formation is already too far ahead to catch up with, they will join another one.

The flocking phenomenon has become a biannual event in Denmark that is known as Black Sun (Sort Sol), where European starlings gather in vast numbers and therefore temporarily darken the sky with their complex flying patterns.

7. A huge flock of starlings over Tondermarsken in southwest Jutland, Denmark:

Image: Tommy Hansen

8. A cloud of starlings during “Sort Sol”:

Image: Christoffer A. Rasmussen

9. Actual migrating bird formation over the Mediterranean:

Image via My Mutual Help

10. Birds on the trail of the airplane or vice versa?

Image: fdecomite

11. Beautiful shot of birds flying into the sunset taken from the terrace of the Kennedy Center in Washington, D.C.:

Image: Mark Zimmermann

The accidental symmetry of the next picture is just amazing. A near perfect V on top of an inverted perfect V.

12. Ten birds flying in formation over the Golden Gate Bridge:

Image: mykaul

13. A flock of barnacle geese over the perfectly flat landscape of northern Germany:

Image: Dirk Ingo Franke

The sub-Saharan red-billed quelea is the world’s most abundant bird species. No wonder then that queleas are able to live and breed in huge flocks, often tens of thousands strong, that can take hours to pass when flying past.

14. Red-billed quelea over a watering hole in Namibia:

Image: Alastair Rae

15. Taking a U – an Auklet flock over the Shumagin Islands, Alaska:

Image: D. Dibenski

16. Flying right at you – a flock of seagulls at Galveston, Texas:

Image: Ed Schipul

A free bird leaps on the back
Of the wind and floats downstream
Till the current ends and dips his wing
In the orange suns rays
And dares to claim the sky.

(The first stanza of Maya Angelou’s poem “I know why the caged bird sings.”)

17. Pelicans escaping the Pacific waves at Cove Beach, Año Nuevo State Reserve, CA:

Image: Wing-Chi Poon

18. A large flock of birds over one of Rome’s many churches:

Image: Anthony M.

19. A semicircle is just a rounded V-formation. A flock of geese close to Chicago’s O’Hare airport:

Image: Doc Searls

20. Spectacular formations of greater white-fronted geese (left), snow geese (right) and Canada geese (background):

Image via Paul Noll

Copycats! A T-bird formation:

Image: Jarrod Ulrich

So, the next time you see a bird formation in the sky, you’ll know that what might look random is actually a coordinated, ingrained pattern.

Source: 1, 2, 3, 4

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