Sunday Science Something #2

The very V behaviours of birds and bowheads

During the month of November I often see Canada geese flying over the fields of San Juan Island. The birds are flying in the typical V-formation, characteristic of migrating geese. I always had a vague idea that they were flying in these formations in order to save energy or that it had something to do with navigation, but I never really bothered to look into why they fly like this -until a recent article in Nature caught my eye.


The distinctive V-formation is known in a number of bird species and has been the subject of interest and intrigue to scientists and non-scientists alike. A team of researchers from the UK’s Royal Veterinary College travelled to Austria to work with the conservation group Waldrappteam – who work with the Northern Bald Ibis, a highly endangered migratory bird that went extinct in central Europe 300 years ago. Waldrappteam rear these birds and teach them to fly and eventually migrate. This is where one of my favourite wildlife themed movies pops to my mind –yep, you guessed it ‘Fly Away Home’. Guaranteed if I am looking after kids I will make them watch it –and I just admitted that here in public....

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So the birds are taught to fly and then to migrate by following a microtlite (exactly as it was in the movie).   This real-life human led migration has been the first successful one of its kind and has opened up all sorts of great opportunities to study birds in their natural flight –something that was too good an opportunity to pass on for the team from Royal Veterinary College. This opportunity to study the birds’ migratory flight behaviours allowed the research team to investigate why these birds would adopt the V-formation during migrations.

source: www.rvc.ac.uk

The researchers attached small data-loggers to the birds and recorded behaviours such as when the birds flapped and how hard they were flapping. Working with these trained birds allowed them to retrieve their data-loggers after each flight –something that is mostly impossible with wild birds, and the data they collected has provided new insights into how these birds migrate and why they adopt the distinctive V-formations.


The team discovered that these birds appeared to have keen awareness of the air structures created by their nearby flock-mates, and even more remarkable was that the birds seemed to have an ability to predict or sense the surrounding air patterns and so how to exploit them to their own advantage. 

Source: Nature

The birds would position themselves in the aerodynamically optimum position within the V-formation, i.e. in the best possible place to take advantage of good upward moving air that was being produced by the bird flying ahead.  Upward moving air helps the birds stay aloft without the bird have to exert excess energy through flapping harder.  When a bird flaps it pushes the air down in order to stay up, this creates a downwash of air followed by an upwash of air.  The birds behind the front bird would position themselves where the upward moving air was located –this meant that the birds would not have to flap as hard to stay up so saving energy. The birds were also found to synchronize their flapping behaviour to further exploit the aerodynamic good upwash air.

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This video beautifully explains what the research team did and what they found. Watch it! 

So these birds are flying in V-formations to save energy on long migrations. But what do V-formations have to do with bowhead whales? In this case the V-formation is does not assist in the efficiency of the whale’s migration, rather it seems to be an important behavioural adaptation for increasing the efficiency of feeding. 

Bowhead whales are baleen whales, they feed by filtering tiny marine animals –zooplankton through their baleen fringed mouth. Occasionally whales are seen in groups ranging in size from two to 14 whales swimming in a co-ordinated fashion such that a front “lead” whale is ahead at the front and the other whales are in a staggered lines behind the lead whale creating a V. This formation is also called an echelon formation.

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As with the V-formations observed in migrating birds, these echelons are dynamic with whales changing positions, and group sizes changing as whales enter and leave the group. While it is not fully understood how this co-ordinated formation assists with feeding it is thought that whales adopt this behaviour when they are feeding on the shrimp-like crustaceans called euphausiids.

Euphausiids, unlike other zooplankton species that the slow moving bowhead whale feeds on, exhibit rapid evasive movements and are thought to be able to move out of the way of the whales gape as it moves slowly forward at the sea surface. So those little critters that manage escape the front whale’s mouth by moving to the side find themselves in prime position to be caught up in the gape of the whale behind.... and so on.  

This type of behaviour has also been observed in surface feeding southern right whales. The whales’ adoption of the V-formation ultimately increases their foraging efficiency while at the same time saving energy by drafting behind the lead whale so reducing the cost of swimming, just as the birds exploit the V-formation to exploit the upwash of the bird ahead to save energy during their migrations. So as an energy saving adaptation the V-formation is Very much a winner! 

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NOAA photo by Craig George. Three bowhead whales feeding in an echelon formation north of Barrow on large concentrations of krill.

SOURCES:

Portugal, S.J., T.Y. Hubel, J. Fritz, S. Heese, D. Trobe, B. Voelkl, S. Hailes, A.M. Wilson & J.R. Usherwood. 2014.
Upwash exploitation and downwash avoidance by flap phasing in ibis formation flight. Nature 505: 399-402

Waldrappteam http://www.waldrappteam.at/waldrappteam/indexl_en.htm

Würsig B, Dorsey EM, Fraker MA, Payne RS, Richardson WJ (1985) Behavior of bowhead whales, Balaena mysticetus, summering in the Beaufort Sea: A description. Fish Bull 83:357-377

Fish, F.E., K.T. Goetz, D.J. Rugh, & L. Vate Brattström. 2012. Hydrodynamic patterns associated with echelon formation swimming by feeding bowhead whales (Balaena mysticetus). Marine Mammal Science. 29(4): E498-507