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The mission statement of the American Federation of Aviculture 

 (AFA) is "To preserve avian species on a worldwide basis". To achieve this 

 mission requires that we have to maintain genetic diversity in our captive 

 populations in order to preserve the fitness of species in captivity as close as 

 possible to their wild counterparts. To do otherwise would foreclose future 

 conservation options. Zoological Parks have the same mission regarding 

 captive populations, but have limited space and funding to accommodate all 

 the species needing a captive-population hedge against extinction. Zoological 

 institutions are often referred to as being analogous to "Noah's Ark". 

 However, there is concern about how many and which species can be 

 accommodated in the Ark, and how many individuals of each species will be 

 necessary to survive a trip of unknown — but likely very long — duration. The 

 private sector can expand the Ark to a "fleet" allowing for more species and 

 greater survival rates. 



Given the fact that preservation of genetic diversity of birds in private- 

 sector collections is important, still leaves the unanswered question of how 

 many birds of each species are needed? As must be well-known to Dr. 

 Beissinger, the concept that a nucleus population of 50 to 75 birds can be 

 managed to maintain the genetic diversity of a captive population over the 

 long-term has been discredited. In a 1993 paper in Zoo Biology (12), pages 535 

 to 548, Kevin Willis and Robert J. Wiese evaluated the premise that a small 

 nucleus population (50 to 75 individuals) supplemented by periodic 

 importation of wild-caught animals could be used to maintain the same 

 amount of gene diversity as larger populations that do not import wild- 

 caught animals. Assuming a "perfect population" regarding breeding 

 population size, sex ratios, productivity etc. (all of which would maximize 

 retention of gene diversity) mathematical models were used to conduct a 

 comparative analysis. Even for this unrealistic "perfect population" the 

 results were staggering. For populations of 50 to 100, 10 to 20 times more 

 wild-caught animals were required for each generation than had been 

 suggested based upon untested theory. The results showed that if the 210 

 species recommended to be managed in this fashion were established with 

 total captive population sizes of 100 each, then 5,040 new wild-caught animals 

 would have to be imported each generation to maintain 98% of the original 

 gene diversity. The authors concluded that, "clearly, this approach is not 

 practical for application on a large scale". AFA concurs with this and with the 

 four conclusions of the paper: 



" 1. Regular importation of wild-caught animals will allow 

 continued maintenance of gene diversity in captive 

 populations. 



2. The Nucleus I population concept, as defined and promoted 

 by the CBSG, would require 10-20 times greater importation 

 rates than indicated by the CBSG. This factor makes wide 



