Developments in Brief : Gulls of Mono Lake Are Going Home Again, Thanks to Rising Water Level

More than 1,200 California gulls have recolonized their former nesting grounds on Mono Lake’s Negit Island. In 1978 and 1979, as many as 33,000 gulls were forced to leave the island when diversion of water from the lake lowered the water level to expose a land bridge that allowed coyotes to attack the gulls’ nests.

The Los Angeles Department of Water and Power had diverted water from four of the lake’s five tributaries to supply water to the city.

In the recent seventh annual census of Mono Lake wildfowl, biologist David Shuford observed 636 nests with eggs on the island, more than six times as many as last year. The gulls began to return to the island last year after heavy snow runoff in 1982 allowed the DWP to halt the diversion.

Since then, the water level in the lake has risen by more than nine feet, although the remaining predators on the island were not removed until last year.

Most of the gulls had moved their nests to much smaller islets around the shore when the lake water receded. The recent rise in the water’s level had reduced the amount of space available on such islets and reduced the birds’ reproductive efficiency. The number of fledged chicks dropped from 26,800 in 1976 to an average of nearly 14,000 in recent years.