'111^ 



A further analysis of the data disclosed when 

 and why color tags are lost. Almost all birds re- 

 tained their tags from 1 to 4 months (97.3 percent 

 of 1,291 recoveries), but substantial losses occured 

 thereafter; 55 percent of the tags were retained 

 from 5 to 8 months, 28 percent from 9 to 12 months, 

 and 8 percent from 13 to 16 months. Loss of plas- 

 ticizer from the plastic, causing brittleness of the 

 tag, was the major reason for tag loss. 



Ecological relMions of robins to fruit in Massa- 

 chusetts. — Basic research on population compo- 

 sition and behavior of a chief fruit crop offender, 

 the eastern robin, was imdertaken in 1964 by the 

 Massachusetts Unit. The main source of data was 

 from 281 wing-tagged robins, each of which could 

 be individually identified by these symbols. Move- 

 ments of the birds were studied in order to deter- 

 mine their relation to commercial fruit crops. It 

 was found that breeding males may travel up to 

 2 miles in search of food, but most feed within a 

 quarter of a mile of the territory. 



Robins have well-defined habitat preferences 

 for nesting, studied by comparing two represen- 

 tative habitats; and statistical tests showed a 

 significant difference in nesting success between 

 the habitats. Three peak hatch periods showed 

 that young of the year were mobile by the time 

 fruit crops such as raspberries, blueberries, and 

 peaches had ripened. Robins fledged on territor- 

 ies having poor food traveled to areas with abim- 

 dant food, and parent robins were observed to lead 

 young directly to nearby food sources. A high 

 percentage of the depredating birds were young of 

 the year. It becomes obvious that, for extensive 

 orchards, the best control may well be elimination 

 of breeding habitat bordering such plantings. 



Three species of Pacific Ocean birds associated with haz- 

 ards to aircraft are the Laysan albatross (top), black- 

 footed albatross (middle), and blue-faced booby (bot- 

 tom). The airfield at the Midway Naval Station, Mid- 

 way Island, has been appreciably freed of bird hazard 

 by grading and blacktopping wide strips parallel to run- 

 ways, following the recommendations of Bureau biolo- 

 gists. (Photos by Karl W. Kenyon) 



64 



