THE ARCHITECTURE OF SWALLOWS 395 



years there has been a wonderful change in the manner in 

 which the common house martin of Europe builds its nest. 

 Formerly their nests were globular in shape, with a small 

 rounded opening hardly large enough to admit the parent 

 birds comfortably. Such are all the old nests in museums, 

 such the descriptions of all writers, half a century ago. These 

 nests were inconvenient, only one bird could come at a time 

 to the opening to be fed. Long before the young could leave 

 their nest they must have been uncomfortably crowded in 

 their ill- ventilated and close quarters. Some time within the 

 half century this entire species has made a great advance and 

 wonderful changes in the whole style of their nest. Instead of 

 a sphere, the nest is simply hollow, semi-oval, roomy, airy, and 

 comfortable, stronger in its attachments, with increased facili- 

 ties for access, better protected, both from the rain and from 

 enemies. Unfortunately, no one observed just when this 

 remarkable change in their architecture took place. We know 

 not if it was gradual or sudden, or how long it was in becom- 

 ing general. But surely no one can pretend that all this was 

 the result of mere instinct I" 



Connected both with the migration and nidification of Swal- 

 lows are some remarkable facts relating to the return of the 

 same pair of birds to the same nest year after year. In the 

 nature of the case, this is difficult to determine with cer- 

 tainty; but observations which have not seldom been made 

 on birds that were marked by some recognizable peculiarity 

 have established the fact beyond question. Far from being 

 singular, however, it accords with many observations made 

 upon birds of other families. How marvellous, how admirable, 

 how complex and subtile, must be the mental faculties of such 

 humble creatures, who can find their homes again with unerr- 

 ing precision, after journeying for thousands of miles ! 



The eggs of Swallows differ as much as their modes of nest- 

 ing. As might be expected from consideration of the slender- 

 bodied form of the birds, the eggs are rather narrow, elongate, 

 and pointed. In the typical hole diggers, who retain their 

 original habits most tenaciously, the eggs are pure white, as 

 in the case of the Bank Swallow, and as the rule is with birds 

 which, like Owls, Kingfishers, Woodpeckers, and many others, 

 lay in holes. Many Swallows' eggs, however, are colored, and, 

 in fact, profusely speckled with reddish and brown shades. I 

 presume, without the slightest proof, but judging by reason- 



