Monday, December 16, 2013

Pinyon Jay Project Update

GBBO has been continuing its work to better understand the causes behind the rapid, ongoing decline in Pinyon Jays.  This decline of 4-5% per year has been occurring over the last 30 years, and has been well-documented by BBS data. However, its causes have not yet been adequately explained, in part because Pinyon Jays have been a poorly studied species in much of their range and present many challenges for field biologists. Nevertheless, we have been successful in efforts to deploy radio tags on Pinyon Jays, and have over the past year conducted a detailed nest study and habitat use assessment in the Desatoya Mountains of western-central Nevada. 

Although data from the last year are still being analyzed, all of our findings to date are consistent with a picture of Pinyon Jays as a species that prefers transitional ecotones between pinyon-juniper woodlands and sagebrush.  Because many of these mixed-age, mixed-structure transitional areas have been supplanted over the last century by larger and denser pinyon-juniper woodland patches, we are hypothesizing that the Pinyon Jay's preferred landscape has been reduced in extent. This suggests a possible mechanism that may have contributed to the Pinyon Jay's documented declines, and one that has ramifications for current pinyon-juniper woodland management practices. GBBO will continue its efforts on behalf of Pinyon Jays, and we will be presenting our findings and recommendations in publications in the near future.

- John

Tuesday, December 10, 2013

Waterbird Surveys

Dennis and Bob surveying on Walker Lake
GBBO has been monitoring populations of fish-eating birds over the last year on several western Nevada lakes, including Walker Lake and Pyramid Lake. Our monitoring efforts occur year-round, although they are more intensive and frequent during the spring and fall migration periods. Our goals are to better understand how waterbird populations at Walker Lake have, and are, changing as the lake shrinks, as dissolved solids increase, and as fish populations decline. We are also interested in determining the extent to which other nearby lakes "take up the slack" and provide habitat for birds that formerly used Walker Lake during migration. 

At present, Walker Lake exhibits substantially reduced numbers of several fish-eating waterbird species, and very large populations of phalaropes and Eared Grebes, which feed on the aquatic invertebrates that thrive in saline lakes. In these respects, it is becoming similar to Mono Lake, but we consider the situation to be reversible if water deliveries to the lake increase again.  Our monitoring program will continue, and as efforts to increase inflows to Walker Lake bear fruit, we can document recovery of its fish-eating waterbirds.

- John