Table 1. — Weights and measurements of 108 bald eagles collected in Alaska 



1 Number of specimens in parentheses. 



2 Obtained by subtracting weight of the food in the stomach and crop from bird's gross weight. 



3 The laterarmeasurement from wingtip to wingtip when the wings are extended to their limit on a flat 



< The measurement from the tip of the bill to the tip of the longest taO feather when the bird is fully extended. 

 5 The measurement from tip of bill to the feathers at base of the cere. 



NESTS AND YOUNG 



We owe much of our knowledge 

 of the nesting habits of the bald 

 eagle to the initiative and persever- 

 ance of Dr. Francis H. Herrick, 

 head of the department of biology 

 at Western Keserve University, 

 who, during the years 1922 to 1930, 

 conducted intimate studies of this 

 bird in northern Ohio. From tow- 

 ers constructed at the nesting sites, 

 he observed and photographed the 

 courtship, nest building, egg laying, 

 incubation, and raising of the 

 young eagles to flying age. In the 

 course of his studies, an original 

 wooden structure was extended to 

 a greater height, and this in turn 

 was replaced by a steel tower 80 

 feet high. When this tower was 

 uprooted in a severe storm in 1929, 

 a second, 96 feet high, was con- 

 structed and used to the end of the 

 studies. The steel tower, equipped 

 with a platform and blind at the 



top, was moved from one nest to 

 another as required by changing 

 conditions. 



Bald eagles are inclined to use 

 the same nest year after year unless 

 disturbed (fig. 4). Herrick (1924a, 

 p. 94) traced the history of six 

 successive nests in the vicinity of 

 Vermilion, Ohio, over a period of 

 nearly a century. One of these 

 nests, the oldest and the largest, was 

 destroyed during a storm in the 

 36th year of its occupancy. Having 

 been added to throughout the years, 

 it had acquired enormous propor- 

 tions, and near the end of its exist- 

 ence was 12 feet high and 8i/^ feet 

 across the top. The upper surface 

 had an area of nearly 50 square 

 feet and its total weight was com- 

 puted to be about a ton (Herrick 

 1924b). 



Broley (1947) records a still 

 larger nest near St. Petersburg, 



332664—55- 



13 



