7. De uurgemiddelde-grafieken

In the figures the mean numbers of birds per hour per 7-day period for the three Coastal regions ZH, NH and Wd are given (resp. upper, middle, lower figure). In these figures the mean numbers of birds flying N(E)-wards are plotted above the abscis, while the mean numbers of birds flying S(W)-wards are plotted below the abscis. 7-dayperiods in which less than 6 hours per region were available, have not been used in the figures Below each region-figure the percentages of presence are given for each month. These were obtained by dividing the number of hours in a certain month, in which a certain species was seen, by the total number of observation-hours in that month. Thus this value may give an indication of the likelyness of encountering a certain species in a particular month in a particular region