Every migration time birds get left behind. Most die quite quickly – if they can’t make their migration then they are in a bad way. If a sick bird can fly it will have a go, and probably die trying. A swallow that stays in the UK overwinter will have a very low chance of survival so it might as well try to migrate. But for species that come here to spend the winter, spending a summer here is not necessarily a death sentence. Arctic breeding species will even find better conditions here than they might experience further north. So any wintering bird left behind might have a gentle summer to recuperate. In a similar way, some long lived species may even deliberately spend eighteen months in their wintering ground in Africa and skip a breeding season when they have had a hard preceding breeding season. This all came to mind because I was watching an aseasonal whooper swan down at Balcomie this week. There has been one around on and off since the spring: all the other whooper swans of last winter have been gone since April and are in Iceland now. It is tempting to think the worst for this swan, but instead, it may be having a summer off, after a bout of bird flu at the end of last winter that precluded any migration. And next spring it will be in really excellent condition, ready to have a spectacular breeding season in Iceland.
Wild Crail 
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