John Buchan 
The Blanket of the Dark [EPUB ebook] 

Peter Pentecost, from his eyrie among the hazels, looked down on the King’s highway as it dipped from Stowood through the narrow pass to the Wood Eaton meadows. It was a King’s highway beyond question, for it was the main road from London to Worcester and the west for those who did not wish to make Oxford a halting-place; but it was a mere ribbon of rutted turf, with on each side the statutory bowshot of cleared ground between it and the forest fringes. And, as he looked, he saw the seventh magpie.
Peter was country-bred and had country lore in the back of his mind. Also, being a scholar, he respected auspices. So, having no hat to doff, he pulled his forelock. Seven magpies in one day must portend something great.
He had set off that summer morning on an errand for the cellarer of Oseney Abbey to the steward of the King’s manor of Beckley, some matter touching supplies for the Abbey kitchen. The sun had risen through lamb’s-wool mists, the river was a fleckless sheet of silver, and Peter had consecrated the day to holiday.