1. RESULTS and DISCUSSION
Puerto Rican Parrot Aviary Population: Demographic and Genetic Analysis For Management
Joanne Earnhardt, Ph.D.1, Jafet Vélez-Valentin2, Ricardo Valentin3, Brian Ramos Güivas3, Sarah Long4, Colleen Lynch4
1Alexander Center for Applied Population Biology, Lincoln Park Zoo, Chicago 2Luquillo Aviary, U.S. Fish and Wildlife Service, Puerto Rico 3 Rio Abajo Aviary, Puerto Rico Department of Natural and Environmental Resources 4Association of Zoos and Aquariums Population Management Center, Lincoln Park Zoo, Chicago
RESULTS and DISCUSSION
Demographic analysis – observed changes in population size and structure
Steady population growth occurs at both aviaries (Fig. 1)
Production of chicks increases as population size grows (Figs. 1 & 2)
The larger population sizes produce more chicks
INTRODUCTION
3) Genetic analysis of aviary population
The Puerto Rican parrot (Amazona vittata), one of the most endangered birds in the world, declined to 13 birds during the 1970’s due to threats such as habitat changes, predators, and hurricanes. To preserve the species and enhance recovery of the wild population, managers from the U.S. Fish and Wildlife Service and the Puerto Rico Department of Natural and Environmental Resources established two aviary populations (Luquillo and Rio Abajo) and initiated a breeding program. In 2010, after 30 years of successful breeding, more than 225 birds live in two aviaries on the island. For the ongoing reintroduction program, over 100 aviary birds have been released to two sites on the island. The exchange of birds between aviaries as well as releases and captures from the wild has created a complex history of population change. To provide the most effective genetic and demographic management of the combined populations, we developed a centralized database that tracks individual birds from birth to death and used analyses from this database for management decisions.
The goal of our genetic management: to slow the loss of genetic diversity and the accumulation of inbreeding without compromising the high level of production
After 30 years of the breeding program, parrots in the 6th generation are living in the aviaries (Fig. 5).
All birds with known pedigrees are related to other birds in the population.
The scientific management of the population is a challenge due to birds with uncertain pedigrees (ancestral and living); for these birds, genetic relationships to other birds are unknown. To improve the pedigree data, molecular genetic analysis is in progress.
Given the complexity of the known pedigree (Fig. 5), computer analysis is the most efficient method for generating information on genetic relationships.
Birds are paired for breeding based on three genetic criteria: 1) Avoid close inbreeding when relationships are known, 2) Match birds to improve pedigree management (%known) and 3) Match birds of similar known genetic value.
Figure 1: History of population growth. Geometric mean lambda for combined population: ƛ = 1.12
Figure 2: Number of hatches at both aviaries over time. N=590 hatches.
Age of birds selected for release changes the population structure (Fig. 3)
Population structure impacts the future growth potential; when young birds mature they, in turn, contribute to population growth
Careful monitoring of population structure is necessary to retain high reproductive output
METHODS
The team from Lincoln Park Zoo, the Luquillo and Rio Abajo Aviaries selected PopLinka as our database application because it was developed for data collection and analysis of small managed populations (such as the programs of the Association of Zoos and Aquariums, AZA). For each individual parrot, the variables recorded in the studbook database are: hatch date and location, parentage (dam and sire), sex, transfer date and location, offspring, death date and location as well as unique identifiers and management comments. Even though other studbooks had been created (and abandoned) in the past, we found reconstructing the 37 year history of 702 parrots to be challenging. The database continues to grow as hatches, releases, and deaths are entered by the aviary staff. Four population biology workshops (2007, 2008, and two in 2009) have focused on 1) standardization and consistency of data, and 2) sessions on genetic and demographic concepts and analysis to be used for management decisions.
Figure 5: A diagram of the complex pedigree for the combined aviary population.
Figure 3: Effect of releases in 2007 on age structure of combined aviary population. On left, age structure before release; on right, age structure after release of 1-2 year old birds.
2) Demographic analysis – projected changes in population size and structure
Using data from past hatch and death rates, the ZooRiskb model application can project future production of offspring in the aviary
By modeling different rates of harvest from future populations we can anticipate the reduction in aviary population size (Fig. 4)
Managers can anticipate numbers of birds available for release to the reintroduction program
CONCLUSIONS
The centralized database improved the population analysis process.
Collaboration between aviary staff and population biologists was essential to the success of the project. Experienced aviary managers posed the management questions and challenges; Lincoln Park Zoo staff used their expertise in scientific management of zoo populations.
With science-based management, the successful breeding program can act as a source for birds to be released in the reintroduction program.
Figure 4: Model projections for change in size of the Puerto Rican parrot aviary population following harvest for reintroduction. Three different management scenarios: ‘No harvest’ scenario retains all offspring in the aviary population ‘Projected harvest’ removes a range of 2-10 parrots for release/yr (allocation goals from Recovery Planc). ‘Extreme harvest’ selects 8 additional birds/yr. Solid lines are means from 300 iterations and dotted lines are +/- 1SD.
REFERENCES
a. Faust et al PopLink
b. Earnhardt et al ZooRisk: A Risk Assessment Tool.
c. U.S. Fish and Wildlife Service Recovery plan for the Puerto Rican Parrot
ACKNOWLEDGEMENTS
The authors and the parrots thank Carrie Schloss and Kate Schowe for their diligent pursuit of complete and accurate data on this species history in the aviary. .