Migrations of Birds
نویسندگان
چکیده
منابع مشابه
The genetics of human migrations
W hen our human ancestors began to migrate from the African savannahs across the Alps into Northern Europe and Asia between 200,000 and 60,000 years ago, they encountered a colder climate, different food sources and new predators. Inevitably, evolution began to work on those wandering tribes: their skin became lighter, their metabolism adapted to new food sources, and their immune system had to...
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United colours: Some may fear immigration as a novel phenomenon endangering established cultural and ethnic units, but research has shown that humans have always migrated and mixed. A recent global study suggests that more than 94% of individuals have significantly mixed ancestry. The picture shows a scene from the Cowley Road Carnival at Oxford, UK. (Photo: Michael Gross.) Migration is one of ...
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Many migrations are temporary – a fact that has often been ignored in the economic literature on migration. Such omission may be serious in that expected migration temporariness can impart a distinct dynamic element to immigrants’ economic behavior, generating possible consequences for non-migrants in both home and host countries. In this paper we provide a thorough examination of the various a...
متن کاملStep-by-Step Migrations
This paper considers a dynamic model of industry location in which there is a tension between two forces. First, there is the agglomerating force of preference of intermediate input variety that tends to keep an industry at its original location. Second, other location factors matter and these tend to pull the industry in the direction of a new location. A crucial aspect of the model is that th...
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— Swallows of the north temperate zone display a wide variety of territorial behaviour during the breeding season, but as soon as breeding is over, they all appear to adopt a pattern of independent diurnal foraging interleaved with aggregation every night in dense roosts. Swallows generally migrate during the day, feeding on the wing. On many stretches of their annual journeys, their migrations...
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ژورنال
عنوان ژورنال: Nature
سال: 1879
ISSN: 0028-0836,1476-4687
DOI: 10.1038/020219b0