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Do swallows fly continually during their migration north or south, or do they rest now and then?

Sent in by Lois-Anne Brown, South Africa

Adult and juvenile swallows start to move south by mid-August as the autumn migration begins. Autumn migration is rather drawn out with birds moving short distances every few days to settle at lower latitude roosts. The average body mass of the birds using such roosts gradually increases into the autumn. As the weather becomes less stable, this essentially forces the push southwards.

For example, Irish breeding swallows cross into Wales and then southern England during August. The vast majority of British breeding birds then leave our southern shores during September with gradual southerly movements.

The spring migration is a far more straight through run of affairs - the birds have more of a necessity to get where they are going. There is a high level of competition amongst males to secure a mate and nesting site.  In spring, experienced birds may be able to return from South Africa in about five weeks at a speed of about 300km per day.
 
Although swallows are thought to exclusively migrate long distances each winter to equatorial regions, a substantial minority winter between their breeding territories and wintering strongholds.

Swallows breed across Eurasia, from Morocco to Ireland and Norway in the west and on similar latitudes across to Japan and southern China. They also breed extensively across North America.

In winter, they are found widely in Africa south of the Sahara, from Pakistan, to New Guinea and northern and central South America.

Within Europe, a few straggler birds winter in southern and Western Europe and are recorded annually in Southern Spain. In recent years, a few swallows have with increasing frequency been recorded over wintering as far north as Britain and Ireland– a probable indicator of the effects of climate change. Small numbers winter regularly in North Africa and there are also small resident (or partly resident) populations in eastern Mediterranean countries.

From bird ‘ringing’ we know that juvenile dispersals begin in July. Newly fledged birds stay around the breeding site, being fed by their parents for several days. Earlier broods can stay put around the nest site for as long as six weeks. Juveniles then enter communal roosts (getting used to the area they will return to next year) while adult birds finish the late broods (as many as three per year).

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