Natural Perspectives:

By tagging these fish and tracking them with acoustic telemetry, Farrugia and Espinoza discovered where they roam in the bay. Gray smoothhound sharks are more active than guitarfish, moving about the bay more. Guitarfish tended to stay in smaller areas. But how they discovered this was nearly as interesting as the findings themselves. After seining the bay for sharks and guitarfish, they attached an acoustic emitter that broadcasts sound in a range that is inaudible to fish. Then these poor graduate students had to motor around the bay in a boat, taking GPS readings every 10 minutes for 24 hours to create a tracking map of the movements of the fish. Ah yes, we remember having to do 24-hour time points back in our graduate school days. There must be a law somewhere that says graduate students have to stay up all night in order to gather data for their theses.

Fish weren’t the only things discussed at this meeting. Birds got their fair share of coverage as well. As anticipated, birds love the new full tidal basin. Terns and plovers have taken to the new sandy nesting areas like, well, like ducks to water. Rachel Woodfield of Merkel and Associates said an average of 8,000 birds a day use the full tidal basin at Bolsa Chica, with Western sandpipers being the most abundant species. Overall, shorebirds are the major users of the new inlet and associated mudflats, but upland birds, ducks, and aerial predators such as terns and pelicans are also abundant.

The bird species monitored most closely were Western snowy plovers and California least terns, which are threatened and endangered, respectively. Both species nest at Bolsa Chica.

In 2008, preliminary data indicate between 42 and 147 plover chicks fledged out of 193 eggs laid. That seems like a huge range, but remember the chicks hatch at different times and run around like crazy when they aren’t hiding, which they’re experts at with their cryptic plumage. Further analysis should refine that data range. Either way, the 2008 season was an improvement over the 25 chicks that fledged in 2007, out of 143 eggs.

The improvement in nesting success seems to be due to the use of metal cages, called exclosures, which are put over snowy plover nests. This keeps out predators such as coyotes and great blue herons, as well as the thousands of terns that nest nearby.