Migration speeds of birds

This entry was posted Wednesday, 17 November, 2010 at 9:46 am

The speed of migration is different for different species, depending on when they migrate. A new study has found interesting differences in the migration speeds of early and late migrants between Europe and Africa. Do Indian migrants show similar patterns?

by Raman Kumar

Raman Kumar is a birder and researcher based in Dehradun who studies human impacts on bird communities. He is currently assessing how woodpecker species in the sal forests of Uttarakhand are affected by different forest management systems. Raman can be contacted at cyornis[at]gmail.com.

Long-distance migration is a demanding exercise, particularly for small passerine birds that weigh only a few grammes. Flying hundreds to thousands of kilometres – often non-stop – is a great strain. In addition, weary migrants have to contend with predators, rough weather and uncertain stopover conditions along their route. And as if all this were not enough, they also have to reach their destination in time to compete for good wintering or breeding sites.

Given all these challenges, how quickly should birds attempt to complete their migration? The answer to this depends on the costs and benefits in terms of energy, time, and security. For example, birds often have to make stopovers to feed and replenish their energy reserves before continuing migration. Flying too fast may consume their energy reserves too rapidly, and this could prove fatal. On the other hand, flying slowly might mean a delayed arrival and a consequent risk of better foraging grounds already having been taken over by competitors.

The speed of migration may also depend on migration distance. Studies have shown that birds that start their autumn journey early fly at greater speeds than those who start later; this may be because early-migrating birds often need to cover larger distances than do late-departing ones that are bound for relatively closer destinations.

The record for the non-stop long-distance flight is held by the bar-tailed godwit [1]. An individual that was radio-tagged in New Zealand flew 11,000 km to Alaska in a mere eight days, without stopping! Passerines (sometimes called “perching birds”) can travel as much as 300 km in a single day, but their effective speed (including stopovers) over the entire journey is typically 27–75 km per day [2]. Some of them progressively speed up as they move to wintering grounds in the tropics. For most passerines the spring return to breeding areas is traversed much faster (by almost 20–60%) than the autumn migration, possibly due to longer daylight hours or better nutrition along the way.

A recent study [3] has assessed speeds of passerines that migrate long-distance between Europe and eastern Africa. Of the 11 species studied: marsh warbler, sedge warbler, red-backed shrike, thrush nightingale, nightingale, willow warbler, garden warbler, whitethroat, lesser whitethroat, barred warbler, and spotted flycatcher, the last four also visit India during autumn and winter. The route was divided into four latitudinal sectors (Europe, desert, northeast Africa and eastern Africa) [see Map]. Observations from many earlier studies on ringed individuals at various locations along the migratory route were compiled to calculate median dates of arrival or passage for each species.

The study found that autumn migration speeds in the European sector were higher for those species that started early (e.g. marsh warbler, sedge warbler, nightingale and thrush nightingale). On the other hand, spring migrants in the northeast African sector that started late travelled at higher speeds (e.g. red-backed shrike, marsh warbler, garden warbler and spotted flycatcher). Overall, spring migration time was shorter than that for autumn, mainly on account of relatively faster travel in African and the desert sectors. A speedier spring migration could have evolved due to the competitive advantage for ‘early birds’ who corner better breeding quarters than do latecomers. But there could be another reason for faster travel during springtime. Since days are relatively longer, there is more time available for feeding and hence faster replenishment during the journey.

The Indian subcontinent, like Africa, is an important destination for millions of wintering birds that come down from northern latitudes beyond the high Himalayas. Yet, information about their arrival and departure timing, speeds and migration routes is scant. Research similar to that conducted on the European-African flyways, but conducted in the subcontinental context, could provide important insights about seasonal movement patterns of passerines in India. Researchers do have a certain idea about the autumn departure dates of some species that also visit India from their breeding grounds in Europe [3,4]: yellow wagtails usually leave Russia in late August, chiffchaffs depart in late August or early September, and lesser whitethroats, bluethroats and white wagtails leave around early September. It would be interesting to observe when these enter India and spread across the subcontinent. The two main ways of generating information on the migration of small birds are intensive bird ringing (and recovery) and large-scale observation networks. Perhaps data from the citizen scientists of MigrantWatch will prompt a better understanding of the fascinating phenomenon of seasonal migration.

Note from MigrantWatch. If you are interested you can check in the MW database whether the arrival of Yellow Wagtails, Chiffchaffs, Lesser Whitethroats, Bluethroats and White Wagtails in India is related to their departure times from Russia.

[1] Gill, R.E., Jr., Tibbitts, T.L., Douglas, D.C., Handel. C.M., Mulcahy, D.M., et al. 2009. Extreme endurance flights by landbirds crossing the Pacific Ocean: ecological corridor rather than barrier? Proceedings of the Royal Society-B 276: 447-457.

[2] Newton, I. 2008. The Migration Ecology of Birds. First edition. Academic Press. London.

[3] Yohannes, E., Biebach, H., Nikolaus, G. and Pearson, D.J. (2009). Migration speeds among eleven species of long-distance migrating passerines across Europe, the desert and eastern Africa. Journal of Avian Biology.

[4] Ryzhanovskii, V.N. 2008. Dates and duration of the basic seasonal phenomena in the annual life cycle of passerines of the subarctic zone on the example of the lower Ob’ region. Contemporary Problems of Ecology 1:227-237.

1 Comment to Migration speeds of birds

  1. capt praveen chopra says:

    November 23rd, 2010 at 8:06 am

    I have an understanding that the Passerine migrants take a piggy ride on the backs of the migrating Cranes. This was specfically observed by the ancient Egyptians who noticed little Warbler flying of the back of a Craneonce they knocked one. Any modern day observations or evidence to substantiate the above?? I would welcome a discussion on this as it would be of great value to those studying Migration of Birds.

Leave a comment