SIGHT FIELDWORK AND EXPERIMENTS 65 



Once this method has been successfully carried out the 

 owl will behave in the same way with a live mouse or young 

 rat which has been caught in a "live-trap". Much informa- 

 tion about the quickness of eye and the extent to which the 

 owl can adapt its sight to varying conditions of light will be 

 gained by carrying out such experiments. 



It is, of course, essential that the light in the place where 

 the test is being made must be sufficient for you to see what 

 happens yourself, but it will be found that once one's own 

 eyes have become accustomed to the dim light of a small 

 lamp or torch it will be quite easy to follow what goes on. 

 In the next section which will deal with hearing I shall 

 describe rather similar experiments designed to show the 

 acuteness of an owl's ears. 



Mammals 



In dealing with the sight of mammals in general and with 

 field observations in particular, there is one pitfall which the 

 student must be careful not to fall into. It is all too easy to 

 ascribe to keen sight many displays of behaviour which in 

 fact have nothing to do with sight at all. Sight may be the 

 dominant sense in birds, but mammals for the most part live 

 in a world of sounds and smells. This is not to say that all 

 mammals have poor sight ; but compared with their fantastic 

 powers of scent and hearing, their eyes do not have anything 

 like so much importance as one is often tempted to think. 



Many mammals of varying sizes have very short sight, 

 some have virtually none at all, and most of them see moving 

 objects far better than any object which is still. All field 

 workers know, or should know, that if one suddenly comes 

 across, say, a fox, or even a bear or a rhinoceros, so long as 

 the wind is not blowing towards the animal and the observer 

 stops moving and remains absolutely still, he has a good 

 chance of remaining undetected. He can then frequently see 

 some incident which is well worth while and which he may 

 not get the chance of seeing again. This is an exercise, if not 

 an experiment, that can be carried out as a form of training. 

 A field with a few cows or sheep in it will do for a trial. All 

 one has to do is to see that one approaches up wind, and at 



