PART ITI 
Explorations in Population Dynamics 
of Representative North American Birds 
In compiling avian life tables one is impressed with the 
scarcity of vital statistics for birds. While this perhaps is to be 
expected for the subadult and adult stages in each species, the lack 
of published quantitative information on productivity is astonishing. 
Many of these gaps in the literature can be promptly and easily 
filled, such as the mean number of young per nest in colonies annually 
frequented by banders; others will require more effort, like the 
determination of the percentage of unproductive females in a popula- 
tion or discovery of the age(s) at which certain species begin to 
breed. These are statistics needed for the ornithological handbooks 
of the future; their incompleteness or absence today may often mean 
that an abridged life table based on banding results cannot be either 
verified or expanded into a life table covering all the stages in 
the life history of a species, 
The expository material in the following chapters is, for 
the most part, segregated under four headings for each species, 
Literature on Productivity and Survival, Banding Work in North 
Kmerica, Characteristics of the Sample Studied, and Abridged Life 
Tables. Commentary material has been generally divided under two 
headings, Age Ratios and Productivity and Population Dynamics. 
These two represent a discussion of the results and an attempt to 
integrate (where possible) the literature on productivity with the 
statistics obtained from abridged life tables. In the longer 
chapters, this. breakdown of description and discussion is less clear 
cut. It is the purpose of Part II to present for biologists and 
conservationists survival and mortality statistics which, for the 
most part, can be used as yardsticks to assess the stability of bird 
populations. 
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