August 29, 1913] 



SCIENCE 



307 



liavior in other directions, and in other species 

 of birds. They do not comport with the work- 

 ings of instinct in the great avian class. 

 Flight, diving, the capture of food and its 

 treatment, all seem to be as certainly provided 

 for in the inherited stock-in-trade, as either 

 nest-building or song. Young gulls, up to the 

 time they take to the water, beyond which I 

 have never been able to watch them closely, 

 certainly get no direct instruction in regard to 

 their food, but plenty which is indirect, and 

 from the time they desert the family preserve 

 they feed abundantly on insects. The parent 

 is not only alma maier, but the great quickener 

 and director of inherited impulses in the 

 young, while at the same time she is the most 

 fascinating model for them to copy. Aside 

 from bodily protection and other minor serv- 

 ices, the lack of this parental factor is hardly 

 appreciable in the incubator-reared chick, but 

 is much more apparent in a hand-reared 

 American robin or nestling of any other 

 altricious species, where the transition between 

 simply taking what drops from heaven, and 

 going about to search for it, are more difficult 

 to compass. The impulses are in any case 

 natural, though they can not be forced. That 

 there is a " school of the woods " we do not 

 deny, but we regard it as an easy " school," in 

 which the " teacher " has a natural gift to im- 

 part and the " pupil " an inherited tendency to 

 receive. 



It is gull-nature to dally with the food in the 

 presence of the young, laying it on the ground 

 and picking it up again, and even putting it 

 back in the " pocket," if it is not quickly 

 mastered, and it is gull chick-nature to follow 

 every movement of the parent, putting head to 

 the ground to get the food, when this is 

 dropped. In such ways, perhaps, a useful les- 

 son, in looking to the ground as an early source 

 of food, is gradually instilled. But this is 

 probably of small consequence, for most inex- 

 perienced birds peck instinctively at attrac- 

 tive objects, and aU the more readily if these 

 are in motion. 



Young hawks, which we have taken from the 

 nest before they were able to stand, and reared 

 in cages, when first introduced to live prey, 



such as frogs, rats and pigeons, dealt with it 

 in every case in the most uniform and precise 

 manner, and this way was characteristic of 

 their race. Before getting such food they will 

 even seize chips and grass, and practise what 

 we may call " play at catching frogs and mice." 

 They will approach the chip cautiously, crouch, 

 squeal, strike, seize, and spread over it as if it 

 were really alive, inflicting blows upon it with 

 the tearing, ripping-up motion, with which 

 they would treat an actual frog or a piece of 

 meat. 



What then was such a bird as the grebe, 

 referred to above, about, when unceremoni- 

 ously ducking its youngsters? It might be 

 that it was imparting a genuine lesson in 

 diving, of the direct sort, that is, given with a 

 motive, in recognition of its progeny's needs, 

 but we have gone to this length to point out 

 that this supposition does not exhaust all the 

 possibilities. It might be that the parental 

 instincts were on the wane, or that their 

 sequence was disturbed, for many birds, of 

 which the moor hen has been noted by 

 Howard, instinctively drive off their young, as 

 soon as they are able to shift for themselves, 

 teasing, pecking, and harrying them unmerci- 

 fully. It would be important to ascertain if 

 the grebes ever display the same instinct. A 

 wider knowledge of grebe-play, cleaning, and 

 other instinctive procedure, might afford fur- 

 ther suggestions. 



We could refer to parallel and even more 

 striking cases in illustration of the difficulties 

 of interpretation. During courtship most 

 birds perform antics of some sort, in the course 

 of which they spread and move their wings 

 and tail and erect their feathers. Since many, 

 like the gay and lordly peacock, are richly 

 decorated, what more obvious interpretation 

 than that this spreading is a form of display, a 

 showing off of all their finery, in order to 

 charm the female. This, as is well known, was 

 Darwin's interpretation, and formed the basis 

 of his theory of sexual selection, or as it is now 

 often called, preferential mating. But more 

 recent and more exact studies upon the whole 

 course of sexual behavior, of which I would 

 cite particularly the illuminating work of 



