4 2\^BSTS AND EGGS OF BIRDS. 



loosely built, some of the eel-grass hanging down at least ten 

 inches below the rim of the nest. The inner lining was made 

 in the common way, of the usual grasses. One of the nests 

 which he obtained had a few dead leaves in its base. Finally, 

 the collection of Dr. Wm. Wood, of Connecticut, contains 

 three robins' nests, all built during the same season, within the 

 same tobacco-shed, and made wholly of bits of tobacco-twine 

 woven inseparably together. Presumably, these three nests 

 were made by the same pair ; and Dr. Wood is reported as 

 inclining to the opinion that two of them, at least, were made 

 before any eggs were laid, since he has known of such a case. 

 Such exceptions to the rule seem fairly to suj^port Dr. C. C. 

 Abbott's clever explanation, lately advanced, of the use of mud 

 by the robin alone among the thrushes ; for, leaving out an 

 occasional scant supply in the nest of the wood-thrush, none 

 of the other species employ it in their architecture. Dr. Abbott 

 considers it probable that, at the close of the glacial epoch, the 

 robin was among the most venturesome of the birds to move 

 again into the new territory slowly yielded by the ice, and there 

 found it needful to fortify its home very stoutly by thick walls 

 of mud against the arctic and changeful temperature ; and that 

 it has persisted in this practice, deriving a benefit from being 

 able to set at breeding so much earlier in the season than its 

 more poorly-housed relatives. Dr. Abbott adds that the ten- 

 dency of all variation in the modes of nest-building practised 

 by birds now is, he thinks, toward greater simplicity. The 

 cases cited above, of the robins which built their nests without 

 mud, might be considered as examples of this I suppose. 

 Possibly the wood-thrush used to build a wind-proof home 

 of mud, but has now almost wholly abandoned it. It must be 

 confessed, however, that I find a circumstance militating against 

 this theory in the habits of the blue jay {Cyamira cristata)^ 

 which builds an open nest in the cold north, and one largely 

 composed of mud in the hot south ; but this may perhaps be 

 explained by saying that the bird finds the chill and solid earth 

 a cooler and cleaner house-material in the dry south than veg- 

 etable matter, which in the north, under a diflbrent climate, it 

 prefers. 



