What birds were they? (...) He listened to the cries: like...

What birds were they? (...) He listened to the cries: like the squeak of mice be- hind the wainscot : a shrill twofold note. But the notes were long and shrill and whirring, unlike the cry of vermin, falling a third or a fourth and trilled as the flying beaks clove the air. Their cry was shrill and clear and fine and falling like threads of silken light unwound from whirring spools.