First Eared Grebe count of the season a successSeptember 23rd, 2013 by Julia, Project Specialist
Happy fall from the Mono Basin! Last night, summer ushered itself out with a lovely, recharging evening rain followed by a morning charmed by the first snow of the season. The Sierra Nevada peaks to the south and west of the basin sported white dustings of snow this morning. Up into the mountains, Yosemite National Park received as much as four inches in places—enough to close Highway 120 for much of the morning!
With the arrival of fall comes time for the annual count of North American Eared Grebes on Mono Lake. After the summer breeding season, over 90% of the entire North American population of Eared Grebes migrates to two lakes in the United States: Mono Lake and Great Salt Lake, where the adults undergo body and wing molt. The fact that almost the entire North American population of grebes concentrates at two geographically restricted sites is highly unusual for any migratory species, and this makes them an ideal candidate for monitoring outside the breeding season.
Canadian biologist Sean Boyd, a leading researcher of Eared Grebes has been coordinating annual grebe counts on Mono Lake each October for many years. Past counts have found as many as two million Eared Grebes—about 30% of the entire continent’s population—confirming that Mono Lake is the most important fall staging site for Eared Grebes in North America. Because Mono Lake supports such a high percentage of the grebe population, the Mono Lake census provides insight into the overall state of the Eared Grebe population in North America. In light of this, the Mono Lake Committee has volunteered its efforts to the project during the past five years. To conduct the counts, we use aerial photography to estimate the number of grebes staging on Mono Lake in the fall. Since 2008 the 2–3 hour flights over Mono Lake have been successful in providing Dr. Boyd with the data needed to produce a tally of migrating Eared Grebes.
This fall brings an exciting change in the usual Eared Grebe count protocol. This year, Dr. Boyd would like to conduct five counts instead of the usual one. So far, he has counted grebes in mid-October, a time when abundance is assumed to be within a relatively stable period. However, there is reason to believe the timing of peak Eared Grebe abundance on Mono Lake has shifted. Dr. Boyd therefore needs to know if variation in the shape of the population curve is occurring so that he can compare the mid-October counts across years and over the long-term.
We are happy to announce that we successfully conducted our first count of the season last Wednesday, September 18. The morning was calm—perfect for photography of the lake surface from the open window of a small aircraft. The resulting photographs await analysis by Dr. Boyd. We are pleased with the success of the first count and look forward to the next count, which is tentatively scheduled for October 2. Stay tuned for updates on the progress of our counts!