Counting the glyphs from the beginning of period no. 1 we arrive at 27 respectively 29 for these birds. I have made a table showing this.

27 stands for the number of nights the moon is potentially visible and 29 nights are needed to reach next month (at least half of the times).

Therefore these two birds must be located exactly where they are, which happens to be in the 4th period (as I see them).