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ship night and day. To me, however, it appears incredible that any animal should be able to 

 undergo so much exertion for so long a time without taking rest. Mr. Gould says that birds 

 caught and marked are generally seen next day ; but such is not my experience. I have some- 

 times marked ten or twelve Cape-pigeons in a day, and seldom seen one again. Mr. Gould, 

 however, is quite right when he says that sometimes a marked bird turns up after being absent 

 for two or three days ; and how can this be accounted for by the theory of the birds constantly 

 following the ship % Most of the Petrels, more particularly those that burrow or live in holes in 

 rocks, are no doubt nocturnal in their habits when they are on or near land ; but when they are 

 at sea they all become more diurnal. A few can certainly be often seen flying under the stern 

 at night ; and once, when I was keeping the middle watch, at about 1 A.M., a Cape-pigeon, in 

 crossing over the ship, struck a rope and fell on deck. Still they are never numerous, and where 

 there were fifty or a hundred birds in the daytime there are only one or two at night. Their 

 defenceless condition is, as far as I can see, the only reason for the Petrels hiding themselves by 

 day and flying by night ; for the oceanic mollusca &c. on which they feed are equally diurnal and 

 nocturnal. At sea, however, where they have no enemies to fear, and no holes to hide in, the 

 conditions are quite different ; and it is then better for them to take their rest at night and to 

 be alert and feeding in the daytime ; and they change their habits accordingly. I therefore 

 believe that, although a few may follow a ship for a night, most of them sleep on the sea ; and in 

 the morning, knowing very well that a ship is the most likely place to obtain food, they fly high 

 with the intention of looking for one. Some find the ship that they were with the day before, 

 some another one. In the latter case, if the second ship is going in an opposite direction to the 

 first, they are never seen by the first again; if, however, the course of the two ships is the same, 

 the bird might very likely lose the second ship, and rejoin the first after a lapse of two or three 

 days. A height of 1000 feet would enable a bird to see a ship 200 feet high more than fifty miles 

 off; and often, although unable to see a ship itself, it would see another bird which had evidently 

 discovered one, and would follow it, in the same way that Vultures are known to follow one 

 another. This opinion is much strengthened by the fact that at sunrise very few birds are round 

 the ship, but soon afterwards they begin to arrive in large numbers ; and I think I may safely 

 say that this is always the case ; for, having had to be on deck from four to eight o'clock every 

 third morning for six of my voyages, and about once a week during my last voyage, I have had 

 better opportunities for observing this than most people." (Ibis, 1865.) 



