Abstract

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Moen, S.M. and H.B. Tordoff. 1993. The genetic and demographic status of peregrine falcons in the upper midwest. Report submitted to the Nongame Wildlife Program, Minnesota Department of Natural Resources. 84 pp.

Abstract:

Chapter 1: Analysis of pedigrees

Once more, Peregrine Falcons are breeding in the Upper Midwest after about three decades of absence and 11 years of successfully hacking birds into the wild. The success of the peregrine recovery effort in the Midwest can be tallied by the genetic condition of the new population as well as by counting pairs in the wild. Pedigree analyses indicate that the Peregrine Falcons breeding in Upper Midwest (including Winnipeg and St. Louis) are relatively related (mean kinship falls between 0.026 and 0.053) and are moderately inbred (inbreeding coefficient is no less than 0.014). The high average relatedness of the population suggests that the inbreeding coefficient will rise as the population moves from being supplemented with hacked birds to becoming self-sustaining.

The relative importance of genetic, demographic, and environmental conditions in driving the founding event of this new population is uncertain. Particular individuals and pairs have been more successful than expected at producing offspring that survives in the wild. This suggests a genetic component to survival. However, the survival of the nest mate (not necessarily a sibling) also appears to positively influence the survival of a fledgling suggesting an environmental component to survival as well. The subspecific condition of an individual does not seem to influence its success since pure F. p. anatum birds survive at a similar rate to pure F.p. pealei individuals and the ratio of subspecies fledged and those breeding is similar. A fledgling's chance of survival does not appear to depend on whether it was wild-produced or hacked.

Peregrine releases in the Upper Midwest are virtually over as of fall 1993. Terminating the peregrine release effort should not jeopardize the new population's genetic integrity since the availability of unique genetic information is limited in the captive population. Continued banding and intense monitoring of the new population is essential, however. We recommend continued banding and monitoring of the population at least until the dramatic genetic changes involved in the founding event are over; particularly, we suggest that the level of inbreeding and kinship be calculated annually. A similar pedigree investigation should be initiated for the Canadian release project. Peregrines released in the lower Midwest of Canada and the Upper Midwest of the United States interbreed freely and similar genetic stock supports both release projects. Should further releases in the Midwest be necessary, we suggest using genetically diverse individuals, especially birds that are not inbred and that are unrelated to falcons breeding in the wild.

Chapter 2: Analysis of DNA similarity

We used DNA fingerprinting and HRFLP analyses to quantify the genetic status of the re-established population of Peregrine Falcons in the Upper Midwest. The overall DNA similarity of the wild breeding population as of 1992 was calculated as 36.42 +/- 1.04(SD). Broken down by probe type, the DNA similarity was calculated as 36.21 + 3.20(SD) for the DNA fingerprinting and 36.82 +/- 2.94(SD) for the HRFLP analysis. The captive population, which gave rise to the wild one, had an overall DNA similarity of 32.99 +/- 1.10(SD). Broken down by probe type, the DNA similarity for the captive population was calculated as 39.59 +/- 1.22(SD) for the DNA fingerprinting and 21.86 +/- 1.88(SD) for the HRFLP analysis. The DNA similarity index provides baseline data for future population assessment but does not adequately reflect current kinship levels as expected based on the result of research on other vertebrates. The unique combination of subspecies involved in the release project might account for the poor correlation between DNA similarity and mean kinship. Approximately 12% of the 63 fragments scored in and the two assumed to be in the captive population were missing from the group of falcons analyzed in the wild. Without intervention, the new population was theoretically expected to lose about 9% of the genetic diversity present in the released population. We recommend a DNA analysis of at least the five major subspecies involved in the release project to assess differences in the frequency of fragment occurrences. We also recommend continuation of DNA analyses of wildborn peregrines and their parents in the Upper Midwest to insure accurate pedigree records and enhance the baseline genetic information presented in this report.

Chapter 3: Population viability analysis

The demographic parameters of the Midwest peregrine population are similar to those reported for other populations. Males and females first breed at an average age of 2.4 and 1.8, respectively. Roughly 1.78 young are produced per nesting attempt even though about 25% of nesting attempts fail. The annual adult mortality for females is 14%; for males it is 19%. We used the specific parameters calculated for the Midwest population as input data for VORTEX(c), a model designed to simulate the dynamics of small populations. The results of the simulations reflect the high environmental variance associated with the demographic parameters precluding accurate predictions about population size. High environmental variance increases the likelihood of extinction. The simulations suggest that the continued success of the population is likely if all population parameters are accurate and static for the next 100 years. More information on juvenile survival would be instructive in fine-tuning the model. Without management, the simulated populations had up to a 5.2% chance of becoming extinct within a century. Simulations of the data from the peregrine population in California confirm the modeled results of Wooton and Bell (1992). Additionally, we present extinction probabilities for the peregrine population in California.

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