RECONSIDERATIONS 



375 



had struck a barrier of another sort a barrier of uncleared land, a 

 barren countryside covered with scrub and bracken, where the thistle 

 was unknown a consequent insufficiency of food. 



The period during which the migration of the redpole continued 

 through Tutira was also brief. The barrier to the southern progress 

 of the redpoles was of an exactly opposite sort not bad land, but good 

 land unpropitious environment to a wild country breed, vast stretches 



^> \ *> *^ J *S ^_-? ^.V fC^ "^ 1 *^*> *7 



^ 1 \ x ^^ v -d^ v 8 



Goldfinch passing through " broken in " 



country checked by unhandled bracken 



and scrub. 



Redpole movement checked by 

 grass- lands. 



of grass-land completely cleared of scrub, lacking both food and nesting 

 accommodation. 



On the other hand, the passing of the blackbird and thrush through 

 the station was prolonged for years. There was nothing to check the 

 current of their flow for scores of miles beyond Tutira. There was every 

 inducement to proceed through a warm, highly fertile coastal belt, amply 

 supplied with shrubberies, plantations, and gardens. 



The duration of the weasel trek through the run was more brief 

 than that of any other aliens ; rivers unbridged proved no barrier he 



