Abstract
The purpose of this paper is to examine patterns that have emerged over the past two years in captive breeding programs in the United States of avian species that are generally more difficult to propagate. The data has been collected and compiled by the San Diego Zoo under the direction of Kerry Muller, Assistant Curator of Ornithology. The data surveys were funded by the International Foundation for the Conservation of Birds (IFCB) in Los Angeles, California. All major zoological institutions and several large private collections are represented in the survey as the purpose of the survey is to assist in the management of bird collections through the matching of species sexually and in locating pairs of species with programs intent upon their propagation. The analysis of the data collected to date is viewed by the authors as a beginning in what could prove to be a valuable tool in the management and propagation of avian species in North America.
Although this survey covers many collections and species not covered by other surveys, there is still a dearth of data so far as statistical analysis is concerned. Such a lack of data is probably due more to the unavailability of many species and difficulty in breeding the ones available than to a lack of survey participation. At least partially due to this lack of data we have limited the present analysis to the three largest groups represented in the survey - Anseres, Phasianidae, and Psittacidae.
In the present study the data was obtained from nearly 125 participants in the United States with geographical locations of the participants as follows:
A sample was considered as a survey participant possessing at least a pair of a particular species in a breeding situation. For the species included in this paper the participants had a combined total of more than 1300 samples, i.e., pairs in breeding situations. The data were collected in two surveys covering the two periods 1980 and 1981.
Correlations were sought between the number of survivors and rainfall, altitude, longitude, latitude. The data were analyzed using a computer program for statistical analysis called SPSS and the computer programming necessary for this analysis was done by Mr. Wilbon Davis. The measure of breeding program performance was the ratio of surviving offspring to total breeding stock and only those results which had a less than 1 in 20 chance of being due to luck are included.
Two variables are said to be positively correlated if one increases when the other increases and are said to be negatively correlated if one decreases when the other decreases. For example, if breeding success of a particular species is positively correlated with altitude this would mean that greater breeding success was achieved at higher elevations. On the other hand if there is a negative correlation with altitude for a particular species, then there was greater breeding success at lower elevations. It should be noted that for a correlation to exist between breeding success and, say, elevation, there must be breeding attempts at numerous elevations.
The number r2 is a measure of the degree of influence a change in one variable has on the other. If r2 = 1, the relationship is perfect, e.g., if breeding success of one species were correlated with rainfall and r2 were 1, then breeding success of that species would be 100% predictable from rainfall. On the other hand, if r2 = 0, there is no linear relationship between the variables, i.e., there is no way to predict to any degree of accuracy the breeding success of the species based on rainfall.
In most of our cases, r2 ranged from .10 to . 30. A good interpretation of this is that 10% to 30% of the variance of breeding success is attributable to the indicated variable for the particular species. For example, if breeding success and altitude are correlated positively and r2 = .3, then 30% of the explanation for breeding success is due to altitude. A correlation is dependent upon percent increase in the total captive population and not dependent upon total viable...