Movements of BullfinchesPyrrhula pyrrhulawithin the breeding season

Because most bird-species, while breeding, defend fixed territories in which they raise one or more broods, the breeding season is usually regarded as a period of distributional stability. At this time, birds generally remain resident in their nesting localities, at least until their last young of the year are mobile. However, not all bird species show such strict residency, and the adult breeders of some species have been suspected of making long movements within a breeding season, between successive nesting attempts. The cardueline finches, which exploit sporadic seed-supplies, may be in this category. Individuals tend to settle temporarily in localities where suitable seeds are plentiful, moving on when stocks decline. Perhaps the most extreme example is provided by Common Redpolls Carduelis flammea in Fennoscandia.1,2, In years when the spruce crop is good, birds settle in the southern boreal forests as the cones open in March– April, and raise a brood of young. Then, when the seed has fallen, they move north to their usual breeding areas in the birch zone, and raise another brood there. This movement has not been shown by ringing, but has been inferred from the sudden disappearance of birds from the spruce forests in May, and the almost simultaneous appearance of adults with young in the birch areas. In years with little or no spruce seed, the birds breed only in the birch. Within-season movements over shorter distances have been suspected in other cardueline finches, mainly from fluctuations in the local densities of nesting birds. These fluctuations occur during the course of each breeding season, and nesting birds can appear suddenly late in the season in places from which they were formerly absent.3 Cardueline finches do not defend exclusive feeding territories like many other birds, but nest solitarily or in loose groups, and forage away from their nests in search of seeding food-plants. Such temporary food sources are not defended, and many individuals often feed at the same sites, usually forming flocks which can be seen on any date during the breeding season. I do not know how far cardueline finches range from the nest for food, but individuals of several species can be followed from the nest until they are out of binocular range, and distances exceeding a kilometre would not be unexpected. When feeding young, they generally visit the nest at intervals of 20–40 minutes.3 Here I present evidence from British ring recoveries that some Bullfinches Pyrrhula pyrrhula make movements within a breeding season that are far longer than might be expected from birds on their normal daily foraging trips from the nest. The timing of such movements, and the fact that adults of both sexes are involved, suggests that some individuals could move long distances between broods.