I’m guessing but it seems to me that the White areas were cut away first then a light blue ink was applied to the raised areas and printed. The artist had decided on an edition of 100 so the first colour would be printed 100 times.
Next the lightest blue areas would be cut away and the ochre area printed. At this stage the main shapes of the composition would be established. There would be more cutting away to leave darker parts of the terns and the isolated shadow areas raised. These would be overprinted again with a slightly darker shade of grey.
Finally the whole block would be levelled just leaving the black areas of the birds and the border raised up. A final print of black ink finishes the job.