Birds, Spiders, Brine Flies and Mercury Contamination on Antelope Island

Last Sunday I found this Northern Shrike on Antelope Island enthusiastically singing away as if spring were already in full bloom.  Their predatory habits and interesting behaviors make them a favorite species for me but when I got home that day I read an article in the Salt Lake Tribune that made me wonder just how healthy their populations near the Great Salt Lake really are.    North end of Antelope Island, 2/5/12 The reason for my concern is a bit complex but I’ll summarize:  For over 100 years smelting operations have been responsible for high levels of elemental mercury in the Great Salt Lake and its sediments.  Microorganisms in the lake convert the mercury to methyl mercury which is the toxic form of the element that can be absorbed by tissues of living things.  Brine fly larvae living in the lake then absorb the methyl mercury and when they hatch the adult flies are consumed by spiders living in the vegetation around the lake.  Finally, those spiders are eaten by the many bird species living and nesting along the shoreline.  But very little is known about the movement of mercury compounds through Great Salt Lake ecosystems, including the possible effects of toxic methyl mercury on birds so Westminster College’s Great Salt Lake Institute was recently awarded a $250,000 grant from the W.M. Keck Foundation to study its possible effects.      Antelope Island causeway, 8/29/11 The number and total biomass of brine flies in late summer around the lake literally boggles the mind but this shot should give you some idea.  It was taken in late August of…

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Brine Fly Feeding Frenzy at the Great Salt Lake

The Great Salt Lake in northern Utah is a vital resource for many of North America’s birds.  The lake is 75 miles long, 30 miles wide and has 1680 square miles of surface area and 335 miles of shoreline.  Surrounding the lake are 400,000 acres of wetlands.  Roughly 5 million birds of 257 species rely on the lake and those wetlands for food, sanctuary, breeding and as a migratory stopover. And one of the primary reasons the lake is such an asset for them is the endemic brine fly, Ephydra hians.     Brine flies can be intimidating because of their massive numbers but they are truly innocuous.   They are found only within a few feet of the shore, they don’t bite and won’t even land on humans.  And they’re a huge nutritional resource for birds. In the photo above, the blurry brown bits in the background are brine flies in flight that have been stirred up by the feeding California Gull.  Different bird species have varying feeding methods with these flies – this species often stakes out a few feet of feeding territory on the shoreline and then rushes through the hordes of flies on the sand, stirring them up, and then snaps them out of the air in large numbers.  This bird is looking down the shoreline and preparing for its next run on the flies.       Most of the flies are resting on the sand until the bird makes its run.  As the gull rushes along the shoreline the flies are disturbed into the air and the bird snaps…

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Long-billed Curlews and “Bugs” of Antelope Island

Two days ago we were just about to go home after several photographically unproductive hours on Antelope Island because of a lack of cooperative subjects combined with a “cloud from hell” that hung over the island and ruined our light all morning when I spotted two Long-billed Curlews far below us.   The area was accessible to our vehicle so we decided to investigate.  Both Mia and I are very glad we did!   Canon 7D, 1/3200, f/7.1, ISO 500, 500 f/4, 1.4 tc One of the two birds was this adult, perched attentively on this almost white Tintic Quartzite boulder.   The curlew was very tolerant of us and let us get close and even allowed me to maneuver my pickup for a variety of backgrounds.      Canon 7D, 1/2500, f/7.1, ISO 400, 500 f/4, 1.4 tc This adult was very relaxed in our presence and eventually settled into grooming and preening as it’s doing here.       Canon 7D, 1/2500, f/7.1, ISO 400, 500 f/4, 1.4 tc It turns out that the second bird I had spotted from up above was this juvenile in the tall grasses and the adult had obviously chosen a relatively high perch in order to keep an eye on the youngster (a behavior we’ve seen multiple times in adults with chicks or young juveniles).        Canon 7D, 1/1600, f/7.1, ISO 400, 500 f/4, 1.4 tc We spent quite some time with these two birds – the parent on the boulder and the juvenile foraging in the grasses.  Occasionally the adult would fly off for a few…

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