Belcrossin 1946 deaward#1/2 Species account Bonin Island Petrel Kayson: Covert, dorsal contour feathers + neck, nump) are tipped with pale blue grey. The secondaries & primaries themselves have a blue grey caste which may be no more than a feather bloom or mud pluggage. This entire grey caste, tipping etc is lacking on the adults & the entire dorsal area gives a brown or charcoal aspect rather than grey. The mid dorsal area especially is brown and thus there is very little contrast of the dark head and mid dorsal region. The immatures, on the other hand have the pale grey back & contrasting dark head. Adults show brown caste probably due more to feather wear than actual feather structure (i.e., gray tips are all abraded). 20-21 Due apparently a heavy rain drowned out many of the smaller individuals while we weren't in the area as many are found dead at burrow entrances. Perhaps though these are being deserted by parents and have starved. Estimated 3-5000 immatures. ad- one and go, but could be up to 1000 or any one caught !