50 Years Ago

Why do many birds move around in flocks instead of singly? The advantages to be gained from being part of a group are usually thought of as being either protection from predators or ease of finding food … Krebs et al. … have recently demonstrated that one reason why a single bird may be at a disadvantage when seeking food is that it is unable to exploit finds of food made by its flock mates. Using captive great tits, they showed that the members of a flock “copy” one another. If one bird finds food, the others will find it as well, as a result of searching in the same area ... The exact location of food was, however, not the only thing which the birds could learn from their flock mates. In one experiment, four different types of food container were dispersed throughout the test area. Once one bird had found food in one type of container, the others would search specifically in that type. An interesting finding was that the degree to which the birds copied one another was dependent on the kind of food distribution they had experienced previously. If they had been used to finding a lot of food in one place, they would copy to a greater extent than if they were used to hunting for small pieces of food dispersed over a wider area.

150 Years Ago

When the tenderest cabbages are growing in the early summer, a number of very small caterpillars or larvae may be seen upon the plants, devouring them in a regular and systematic manner ... At first very small in size, the caterpillars do not attract much attention, and especially, as after living for a few days, they hide up out of the light, and look shrivelled and ill. After a short time, the caterpillar in retreat bends its back violently, and splits the skin of one of the rings or segments of the part nearest the head, then a vigorous struggle enables the legs and the head to be withdrawn through the crack, and the larva is noticed to have attained a new skin within the old one. It crawls on to its favourite plant and makes up for lost time, grows rapidly, and really may be said to live to eat. It cares not for its fellows, nor for any other leaves; it is content with its own cabbage, and has no ambition and no desire to quarrel or to move away.