But the herring-gull has a shriller, more piercing voice, and resembles the black-backed species just as, in human voices, a boy's clear treble resembles a baritone.

Both birds have a variety of notes; and both, when the nest is threatened with danger, utter one powerful importunate cry, which is repeated incessantly until the danger is over.

And as the birds breed in communities, often very populous, and all clamour together, the effect of so many powerful and unisonant voices is very grand; but it differs in the two species, owing to the quality of their voices being different; the storm of sound produced by the black-backs is deep and solemn, while that of the herring-gulls has a ringing sharpness almost metallic.
It is probable that in the case I am describing the effect of sharpness and resonance was heightened by the position of the birds, perched motionless, scattered about on the face of the perpendicular wall of rock, all with their beaks turned in my direction, raining their cries upon me.

It was not a monotonous storm of cries, but rose and fell; for after two or three minutes the excitement would abate somewhat and the cries grow fewer and fewer; then the infection would spread again, bird after bird joining the outcry; and after a while there would be another lull, and so on, wave following wave of sound.

I could have spent hours, and the hours would have seemed like minutes, listening to that strange chorus of ringing chiming cries, so novel was its effect, and unlike that of any other tempest of sound produced by birds which I had ever heard.