Bird Migration (Collins New Naturalist Library, Book 113)
Ian Newton
Language: English
Pages: 400
ISBN: B004GXB4WU
Format: PDF / Kindle (mobi) / ePub
The phenomenon of bird migration has fascinated people from time immemorial. The arrivals and departures of different species marked the seasons, heralding spring and autumn, and providing a reliable calendar long before anything better became available.
Migration is shown by many kinds of animals, including butterflies and other insects, mammals, marine turtles and fish, but in none is it as extensively developed as in birds. The collective travel routes of birds span almost the entire globe, with some extreme return journeys covering more than 30,000 km. As a result of migration, bird distributions are continually changing – in regular seasonal patterns, and on local, regional or global scales.
Migration has repeatedly prompted familiar questions, such as where birds go or come from, why do they do it, how do they know when and where to travel, and how do they find their way? In this book, Ian Newton sets out to answer these – and other – questions.
The book is divided into four main sections: the first is introductory, describing the different types of bird movements, methods of study, and the main migration patterns seen around the British Isles; the second part is concerned mainly with the process of migration – with timing, energy needs, weather effects and navigation; the third with evolution and change in migratory behaviour; and the fourth with the geographical and ecological aspects of bird movements.
lower than the 0–3 per cent estimated for other times of year (Ward et al., 1997). In theory, following radio-marked birds on their journeys can also provide information on migration-related mortality, providing death can be distinguished from radio failure or detachment. Of 19 juvenile Ospreys radio-tracked from Britain between 1999 and 2002, only ten seem to have survived the journey to Africa. Two died in the western Atlantic, four in the Sahara, and up to three elsewhere. With the latter
(1985). Factors determining the population size of arctic-breeding geese wintering in western Europe. Ardea 73: 121–8. Ebbinge, B. S. & Spaans, B. N. (1995). The importance of body reserves accumulated in spring staging areas in the temperate zone for breeding in Dark-bellied Brent Geese Branta b. bernicla in the high Arctic. J. Avian Biol. 26: 105–13. Edelaar, P. & Terpstra, K. (2004). Is the nominate subspecies of the Common Crossbill Loxia c. curvirostra polytypic? Morphological differences
high-altitude performance that are matched by very few other animals. Not all birds have such flexibility, however, and whatever the advantages of high-altitude flight, many species seem confined to migrate at low elevations, presumably for physiological reasons (Chapter 4). In the New World, most of the mountain ranges, including the Rockies and the Andes, run approximately north–south, so do not need to be crossed or circumvented by most lower-ground migrants travelling roughly on a north–south
to particular selection pressures, as explained in Chapter 15. Departure from different latitudes: the role of daylength Many migratory species winter over a wide span of latitude. In general, northern breeding populations that winter furthest south, and have further to migrate, start their return migration earliest in spring, whereas those that winter further north start later. In other words, wintering populations withdraw in sequence from south to north, as they return to their northern
km per day. Return of displaced birds to wintering sites All these experiments involved birds displaced from their nesting places, to which they presumably had a strong incentive to return, but similar experiments have involved the displacement of birds from their normal wintering sites. They showed that birds caught as adults were more likely to return in the same or a subsequent winter than birds caught as juveniles, and that the return of juveniles depended on how long they had spent at