10.11.3.2 Birds (2005 Environmental Report
)
C. A. Duberstein and
K. B. Larson
Thirteen of the Biological Resources Management Plan
(DOE/RL-96-32) plots located within central Hanford were
revisited during 2005 to evaluate population trends and
provide information that could be used to support ongoing
risk assessments. These data are also important in evaluating
the response of the bird community after seven of the plots
were burned in 2000 during the 24 Command Wildland
Fire (Figure 10.11.8). Before the fire, 12 of these plots had
a sagebrush overstory and a bunchgrass understory, while
the other was dominated by grasses. The burned plots have
undergone natural vegetation recovery. The fire eliminated
most or all of the shrub overstory, resulting in plant communities
dominated by grass and forb species.
At each plot, at least three 10-minute point count surveys
were conducted during the spring (Bibby et al. 1992). The
total bird count for each plot was divided by the number of
surveys to standardize the data for comparisons.
A total of 1,952 individuals of 42 species were recorded. Western meadowlark (Sturnella neglecta) was the most abundant and most frequently observed species, being observed in 89% of all surveys. Sage sparrows and horned larks (Eremophila alpestris) were also frequently observed, and together these three species accounted for nearly 70% of all birds observed. None of the species observed were listed as threatened or endangered by either the Washington Department of Fish and Wildlife or the federal government. However, the loggerhead shrike (Lanius ludovicianus), merlin (Falco columbarius), and sage sparrow were observed birds that were classified as Washington State Candidate species by the Washington Department of Fish and Wildlife, and the shrike is also a federal species of concern.
Comparison of the abundances of the 12 most numerous species found in 2005 (post-fire) to abundances recorded prior to the 2000 wildfire showed decreases for only two species: white crowned sparrow (Zonotrichia leucophrys) and sage sparrow (Figure 10.11.9). The abundances of two species, loggerhead shrike and horned lark, increased slightly in 2005 compared to pre-fire estimates. For the lark sparrow (Chondestes grammacus), long-billed curlew (Numenius americanus), brown-headed cowbird (Molothrus ater), common raven (Corvus corax), savannah sparrow (Passerculus sandwichensis), and western meadowlark, there were no changes in abundance. None of the changes in abundance was statistically significant (α > 0.05).
Some of the temporal trends in bird abundance detected on the plots were observed elsewhere in the region (cowbird, meadowlark), while others were different than the observed regional trends (horned lark, shrike) (Table 10.11.3). Since most of the birds that breed within Hanford shrub-steppe habitats are migratory and only spend the breeding season in Washington State, it is difficult to determine what factors may be contributing to changes in populations and how much influence any one factor may have.
