I will develop adaptive management strategies for a tropical, globally endangered bird species, the Pale-headed Brushfinch (Atlapetes pallidiceps).
The species was believed to be extinct during 30 years when in 1998 a residual population of 30-60 individuals was discovered (Agreda et al 1999). Despite protection of this last remaining population by Fundacion Jocotoco, a local NGO, the population did not increase until its main threat, high parasitation rates of invasive cowbirds (Molothrus bonariensis) was lowered by a cowbird eradication program (Oppel et al. 2004a). Even though the population of the Pale-headed Brushfinch has grown fivefold since then and now counts about 200 individuals, it is currently unknown whether the population will continue to increase, since the carrying capacity seems to be reached (Krabbe et al. 2011) and genetic impoverishment might additionally threaten this species.
To successfully develop conservation strategies for the Pale-headed Brushfinch, we aim at the following:
- Identification of remaining suitable habitat outside the reserve
Since the species is nowadays confined to a single location, it is very vulnerable to catastrophic events such as locally occurring bushfires. Especially if genetic analyses reveal decreased adaptive potential of the species, a translocation and establishment of a second reserve might be recommended.
- Investigation of cowbird parasitism rates in 2013/2014
Since the first cowbird control in 2003, the population has expanded to higher altitudes and more humid areas of the reserve, a suboptimal habitat for the cowbirds. Possibly the proportion of parasitized nests has decreased and cowbirds no longer remain the main threat for the species, which means funds for cowbird control could be allocated elsewhere.
- Comparison of different habitat management strategies
Semiopen scrubland as preferred by the Brushfinch quickly converts into dense forest unless appropriate measures are applied. Vegetation control by the local park ranger is very time consuming and not feasible across the entire reserve. Controlled fires and controlled pasture outside the reproductive period might be adequate alternatives. Nest searches and behavioural studies in parts of the reserve which had been burnt or grazed intentionally will identify how the different measures affect Brushfinch reproductive output.
- Bottleneck assessment of the Pale-headed Brushfinch
I want to test the hypothesis that the severe reduction in population size has lead to a genetic impoverishment of the species. This could have a large effect on the future fitness of the population, especially considering larger time scales than the current ten year increase. I will apply functional genetic markers, such as MHC genes, and neutral genetic markers, such as microsatellites.
- Population Viability Analyses
Population Viability Analyses (PVAs) allow to estimate the future trend in population growth of the Pale-headed Brushfinch, e.g. to model the long-term effect of inbreeding. PVAs are also successful in evaluating the benefit of different management options beforehand, e.g. a translocation, cowbird control or habitat regeneration. The most effective strategy can then be weighed against its cost and enable an efficient management of the species.
Agreda, A., Krabbe, N., Rodriguez, O. 1999. Pale Headed Brushfinch Atlapetes pallidiceps is not extinct. Cotinga 11: 50-54.
Krabbe, N., Juiña, M. & Sornoza, A. F. 2011: Marked population increase in Pale-headed Brushfinch Atlapetes pallidiceps in response to cowbird control. J. Ornithol. 152, 219-222.
Oppel, S., H. M. Schaefer, V. Schmidt & B. Schröder 2004a: Cowbird parasitism of the Pale-headed Brush-Finch Atlapetes pallidiceps: Implications for conservation and management. Bird Conservation International 14: 63-75.