6. De uurgemiddelde-grafieken
Club van Zeetrekwaarnemers Verslagen , Volume 35 - Issue 1 p. 15- 28
In the figures the mean numbers of birds per hour per 7-day period for the coastal regions ZH (upper) and NH (lower) are given. In these figures the mean number of birds flying N are plotted above the abscis, while the mean number of birds flying S are plotted below the abscis. Periods in which less than 6 hours were available are marked *. Below each region figure the percentage of presence is given for each month. These were obtained by dividing the number of observation-hours in which the species was seen by the total number of observation-hours for that month. Thus this value gives an indication of the likelyness of encountering a certain species in a particular month in a particular region.
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