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Autumn migration at Beidaihe 1986 to 1990 conclusions |
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Written by Martin Williams
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Sunday, 11 November 2007 |
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Page 5 of 7
Appendix B: Histograms showing occurrences of migrants in autumn 1987
Histograms produced by Daniel G. Duff, based on an analysis by John Palfery of a migration log kept by Jesper Hornskov
Histograms are plots of bird-day totals (summed over five-day periods) against time (date) in five-day periods. The date for each species have been separated on the histograms to distinguish be-tween birds visibly migrating (dense hatching) from those birds recorded as present in the area (sparse hatching).
To be included among the migration histograms, a species must have occurred for more than ten bird-days, and the observations must fall within more than one five-day period.
The histograms are split into two sections. The first and main section treats birds specifically identified. Here the birds are listed in order of date of median occurrence, although this is an ap-proximation as the five-day bird-day totals are used in this calculation. Also, the median occurrence date calculated over the period 18 August to 30 November will be somewhat arbitrary for birds with a significant presence at Beidaihe outside this period, in particular for several early migrants.
The second section deals with birds not specifically identified, and here the histograms are in spe-cies order.
The letters beneath the histogram numbers in the first section refer to the histograms in the second section (incompletely identified birds) which might contain records of the species concerned.
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Last Updated ( Sunday, 11 November 2007 )
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