Tuesday, September 21, 2010

Birds and Drought: Palila Follow-Up

As a follow-up to my previous post about the Palila (an Endangered Hawaiian honeycreeper) and drought, I here present quantitative data on the impact of drought on Palila breeding efforts.

Lindsey et al. (1995) presented the results of a 7-year (1987-1993) study of annual survival, age, and sex ratios of the Palila on Mauna Kea, and offered the following observations on the impacts of drought:
The number of nesting attempts by Palila appeared to be influenced by annual differences in precipitation and differences in the availability of immature mamane pods [the principal food source] prior to and during the Palila breeding season (van Riper 1980; P. Banko, unpubl. data). For example, we located 71 Palila nests in our study area during 1991, a year of relatively high mamane pod production, compared to 52 nests during the previous year when mamane pods were moderately available (T. Pratt, unpubl. data). In 1992, when the drought caused an almost complete failure in the mamane crop, we located only five Palila nests [a 92 percent reduction from the average of the previous 2 years]. Adult Palila had higher survival in years when mamane production [and presumably precipitation] was relatively high.
"Hawaii is suffering through an unprecedented drought", with El Nino conditions the last two years having "added new misery to a half-century of declining rainfall on the tropical island chain."

Firefighters fear that "extreme wildfires could destroy native ecosystems and create devastating long-term environmental damage."

Sources:
Lindsey, G. D., S. G. Fancy, M. H. Reynolds, T. K. Pratt, K. A. Wilson, P. C. Banko, and J. D. Jacobi. 1995. Population structure and survival of the Palila. Condor 97: 528-535. URL:
http://elibrary.unm.edu/sora/Condor/files/issues/v097n02/p0528-p0535.pdf

van Riper, C., III. 1980b. The phenology of the dry-land forests of Mauna Kea, Hawaii, and the impact of recent environmental perturbations. Biotropica 12: 282-291. URL: http://www.jstor.org/pss/2387700 [Abstract only]

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