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2007年7月 Reverse Migration - 30th July 2006
Gone are the days when people believed that swallows spent the winter hibernating in mud at the bottom of reed-beds or that young barnacle geese hatched from barnacles growing on the seashore. The point of migration is simple. Entire populations need to follow the seasonal ebb and flow in the food supply. The onset of winter across the Northern Hemisphere displaces millions of birds southwards. However, there is no panic. Routes evolved since the world's climate changed in the wake of the last Ice Age 10,000 years ago provide them with both a timetable and an itinerary for twice-yearly journeys that, on average, span a third of the Earth's circumference Despite the fact that it is still summer here, that migration has already started as birds move south from Greenland, Iceland, Scandinavia and Northern Scotland . Waders are normally the first to be seen moving with our own Common Sandpipers leaving mid July as soon as the young have fledged. Other waders such as Curlew and Oystercatchers are also returning to the coast, following moorland breeding. Passerine migrants to leave soon will be Whinchat, Wheatear and Sedge Warbler, to be followed later by the hirundines, Sand Martin, House Martin and finally Swallow. Prior to departure flocking is often noticed particularly with Swallows.
Migration at this season is a more relaxed affair and birds tend to wait for optimum weather conditions before starting a long flight. The route of day-time migrants is influenced by the nature of the land over which they fly. Coasting - the habit of following a coastline - is a common practice with linnets and meadow pipits. Many species that we think of as resident migrate south only to be replaced by birds from the north and east. This is a complex affair and there is a lot to be learnt, but we can be sure of one thing: they have analysed how this planet works and made themselves masters of survival.
2007年7月 Long-eared Owls - 31st July 2007
Seil Island is home to three species of owl, Barn Owl (Tyto alba), Tawny Owl (Strix aluco) and Long-eared Owl (Asio otus). The most uncommon and lesser known is the Long-eared Owl which is largely nocturnal and is almost certainly under recorded here in Argyll. At rest, the long ear tufts and distinctly orange eyes make the Long-eared Owl easy to recognise. However, in flight they can be confusingly similar to Short-eared Owls. The most obvious features to look for are the uniformly dark under-parts, the lack of a white trailing edge to the wing and less distinct barring everywhere, especially under the wing-tip.
They often roost in small stands of conifers surrounded by open hunting habitat. If you're lucky, you may see the male wing-clapping as he performs his display flight. This involves slow steady wing beats with soft single wing claps below the body every few flaps. Hence you hear several well-spaced claps, unlike the flurry of claps given by a Short-eared. The adults are not particularly vociferous and the females tend to sit tight during incubation. The nest is often laid in an old crow’s nest or a stick nest of similar size.
They breed from February-July, with incubation taking 26-28 days. The young leave the nest after about 3 weeks but cannot fly for another 2 weeks. They become independent after a further 8 weeks. The calls of hungry young are often the first indication that a breeding pair is present. The begging call is a loud and plaintive, high pitched “pee-eh” which can be heard for some distance. Their prey includes small mammals, such as mice, short-tailed voles, and small birds. June and July would be the best months to see them, just before dusk, as the young once fledged are calling regularly for food from their parents. |
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