Info

Proportion migrating

Constant

Variable

Timing

Consistent

Variable

Distance

Consistent

Variable

Direction

Consistent

Variable

bird species from low to high latitudes. It accounts for why some species, such as the Great Tit Parus major or Eurasian Bullfinch Pyrrhula pyrrhula, are essentially resident in some parts of their geographical range, irruptive in other parts, and perhaps regular migrants in yet other parts (Cramp & Simmons 1980, Cramp & Perrins 1993). Each mode of behaviour is adapted to the nature of the food supply in the region concerned, in accordance with their different food plants.

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