Young Robins commonly disperse to breed between 1 and 4 miles from their place of birth, but only 5 per cent, have been found more than 8 miles from … - David Lack

In Lapland, all species start breeding 1–2 months later than in Britain, and the breeding season is much less extended. As compared with Britain, the Corvidae and predatory birds of Lapland lay early relative to the small passerines, but among the small passerines, and also among the predators, the different species tend to breed in the same order relative to each other as they do in Britain.

The limicoline species in June and July, and the passerine species in late autumn, cross the North Sea primarily with easterly winds and hardly at all with westerly winds, whereas in spring they often set out against the wind. This might merely be due to a stronger migratory urge in spring than autumn, but it also seems possible that westerly winds deter migration in autumn because they are so often associated with rain and other unfavourable conditions.

... 'duetting' is uncommon in birds, but has been recorded for various tropical species.