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MIGRATION IN THE OUTER HEBRIDES STUDIED BY RADAR
Author(s) -
Lee S. L. B.
Publication year - 1963
Publication title -
ibis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 80
eISSN - 1474-919X
pISSN - 0019-1019
DOI - 10.1111/j.1474-919x.1963.tb01588.x
Subject(s) - sunrise , passerine , heading (navigation) , geography , oceanography , geology , paleontology , geodesy , meteorology
Summary The main passerine arrivals and departures in the Outer Hebrides in autumn are (i) S.E. from Iceland, presumably of Wheatears and Meadow Pipits in September and of Redwings in October; (ii) E.S.E. from Greenland, mainly of Wheatears; (iii) slightly west of south from the Faeroes; and (iv) with drift by easterly winds, of thrushes and drift‐migrants between west and south from Norway, (v) One W. movement was also recorded. Arriving migrants flew too low over the sea the sea during the second part of the night to be detected by radar, but rapidly gained height at dawn, at which time drifted Continental migrants re‐oriented S.S.W. and S.S.E. (from W.S.W.), but Icelandic and Greenland birds evidently did not change direction. In autumn, the presumed Wheatears, Meadow Pipits and Redwings were far less deterred from setting out by moderate head‐wings or strong cross‐winds than similar birds in Norfolk. But in spring nearly all the sizeable movements occurred with following or light winds. There were three main times of departure from Lewis in autumn, at nightfall (presumed night‐migrants), some two hours before sunrise (presumed night‐migrants again) and around sunrise (diurnal migrants). The presumed Icelandic Wheatears and Meadow Pipits, and until mid‐October the presumed Redwings, departed on the same S.E. heading as that on which they arrived. But after mid‐October the Redwings left almost due south, perhaps a re‐determined heading. On one night in late October about one‐fifth of the presumed southward departure went northwest, apparently because the birds mistook the rising moon for the set sun. Presumed Greenland Wheatears left on the same heading as that on which they arrived, but Continental thrushes, which must have arrived W.S.W., left S.S.W. on subsequent nights. The movements of non‐passerine birds are briefly discussed. In spring, the incomplete observations refer primarily to N.W. departures of Redwings, waders and geese, with some departures N.N.E., presumably for the Faeroes, others E., probably of Blackbirds, and yet others S.E., probably reversed movements.