246 The Naturalist in La Plata. 



bird can pass in and out without turning round. 

 Another species scoops a circular hollow in the soil, 

 and builds over it a dome of fine woven grass. It 

 should be mentioned that the nesting habits of only 

 about fifteen out of the sixty-five species comprised 

 in this genus are known to us. In the genus 

 Furnarius the oven-shaped clay structure is known 

 to be made by three species ; a fourth builds a nest 

 of sticks in a tree ; a fifth burrows in the side of a 

 bank, like a kingfisher. 



The explanation of the most striking features 

 of the Dendrocolaptidas, their monotonous brown 

 plumage, diversity of structure, versatile habits, 

 and the marvellous development of the nest-making 

 instinct which they exhibit is to be found, it appears 

 to me, in the fact that they are the most defenceless 

 of birds. They are timid, unresisting creatures, 

 without strength or weapons ; their movements are 

 less quick and vigorous than those of other kinds, 

 and their flight is exceedingly feeble. The arboreal 

 species flit at intervals from one tree to another ; 

 those that frequent thickets refuse to leave their 

 chosen shelter ; while those inhabiting grassy 

 plains or marshes study concealment, and, when 

 forced to rise, flutter away just above the surface, 

 like flying-fish frightened from the water, and, 

 when they have gone thirty or forty yards, dip into 

 the grass or reeds again. Their life is thus one of 

 perpetual danger in a far greater degree than with 

 other passerine families, such as warblers, tyrants, 

 finches, thrushes, &c. ; while an exclusively insect 

 diet, laboriously extracted from secret places, and 

 inability to change their climate, contribute to make 



