nesting colonies were located in six major marsh communities of the 

 eastern shore and were visited approximately twice a week from 

 late April to mid-August. 



The average clutch size for 537 clutches was 3.3 eggs, with a range 

 of 2 to 5 eggs. The ratio of territorial males to nesting females 

 was 1:1.9. There was direct evidence of double broods by four females. 

 The average number of young produced was 4.2 per breeding female, or 

 8.1 per breeding male. 



Nesting success for the total of 675 active nests was 57 percent, 

 with a range from 38 percent to 69 percent in the colonies. Robust 

 plants that held constant form throughout the nesting season supported 

 95 percent of the nests, and the success of these nests was 58 percent; 

 in contrast, non-robust plants supported only 5 percent of the nests, 

 and the success of this group of nests was only 26 percent. Nesting 

 success varied with height from ground: 45 percent for nests less 

 than 2 feet from the ground, 55 percent for those 2 to 4 feet, and 

 62 percent for those more than 4 feet. Histories of 749 nests were 

 summarized by stages: 749 newly built, 675 with eggs, 424 with nestlings, 

 and 388 with fledging young. (A. A.) 



Keywords: nesting ecology, red-winged blackbird, tidal marshes, Chesapeake Bay 



V-B-46 



Henny, C.J., and V.D. Stotts. 1975. Osprey productivity during the 



mid-1950s in a portion of Chesapeake Bay. Chesapeake Science 



16:219-220. 



While offshore duck blinds in Chesapeake Bay were being surveyed intensively 

 in the mid-1950s to determine use by nesting ducks, information was 

 also collected on osprey nesting. The number of young fledged per 

 active nest was 1.10, which is about the middle of the standard 

 (0.95 to 1.30) necessary to maintain a stable population. Healthy 

 populations consist of 5 to 10 percent of the 2-year-old age class. 



The authors conclude that the observed production rate along the 

 upper eastern shore of Chesapeake Bay in the mid-1950s appeared to 

 be normal or near-normal, based on a small sample. (B.W.) 



Keywords: ospreys, productivity, Chesapeake Bay 



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