Mono Lake gull research update
By Nataniel H. Taylor, Justin Hite, and David W. Winkler
In 1999, a team of researchers from Cornell University augmented the team from the Point Reyes Bird Observatory to carry out annual monitoring as well as to investigate the effects of meromixis on the feeding and productivity of California Gulls at Mono Lake. (Meromixis is a state in which the lake does not completely mix on an annual basis, resulting in a less saline water layer floating on top of a more saline layerfor more information on meromixis see www.monobasinresearch.org/timelines/meromixis.htm.)
Researchers assisted in the censusing of the gulls and began studies directed toward understanding the poor productivity of gull nesting in recent years. Much of the Cornell teams work was involved in developing methods for research and establishing a new plot and observation site on Little Tahiti islet. Relatively small sample sizes obtained last summer are sufficient to suggest the following tentative conclusions:
the growth rates of chicks in 1999 appear to have been slightly lower than those that Winkler observed at Mono in 1980-1982
the rate of gull predation on other gulls in 1999 appears to have been higher than normal
gulls fed their chicks a large amount of alkali fly larvae and pupae, though there are still a lot of shrimp being taken
they also added long-legged fly larvae to their diet, a relatively fresh-water species that has not been common at the lake since the meromictic event of the early 1980s.
Last summers research makes it clear that the gulls are taking substantial numbers of alkali flies, but future research needs to explore just how good alkali flies are as food items. If, as seems likely, the flies are better prey than shrimp, where are the limits to greater use of the flies by the gulls? Click here to read the annual gull research reports online.