Short-tailed Shearwater Ardenna tenuirostris

Medium-sized, dark brown shearwater. Has narrow, crooked wings and flies with quick, snappy wingbeats. Variable underwing pattern, usually rather dark with a less distinct silvery flash than Sooty Shearwater, but difficult to judge depending on lighting. Common in the Pacific Ocean, especially around Australia and New Zealand and up to the Bering Sea. Unknown from South America. Can be abundant in ocean waters off Alaska, gathering in enormous flocks; less common further south. Extremely similar to Sooty Shearwater. Short-tailed is lighter and has more crooked wings; also look for slightly shorter bill and more rounded head.