Tuesday, August 2, 2011
Mitchell's Satyr - a very rare butterfly indeed
As the piping plover field season comes to an end, I will hopefully have some time to resurrect my long dormant blog.
To start what will hopefully be a late summer and fall filled with many nature adventures that I can share on "The Birding Life", I wanted to report on a short trip Nikki and I went on to look for one of Michigan's rarest species, the federally endangered Mitchell's Satyr Butterfly.
The relatively strict habitat needs of Mitchell's Satyr have probably always made it a rare species. However human conversion of wetland habitats to other uses have led to the extirpation of the Mitchell's Satyr from historic locations in New Jersey, Maryland and Ohio, leaving Michigan as the last stronghold for this rare species. In fact of the 17-18 remaining colonies, all are in Michigan except for one last location in Indiana.
As mentioned the Mitchell's Satyr is a habitat specialist. They occur only in fens, which are a type of peat-forming, mineral-rich groundwater fed wetland. Because the groundwater that feeds fens is mineral-rich, fens tend to have a neutral or alkaline water chemistry, opposed to bogs (which people often mistake with fens) which tend to be acidic. In fact, Mitchell's Satyr is almost entirely confined to a type of habitat known as a prairie fen. Prairie fens are a globally rare and biodiversity rich habitat type dominated by tallgrass prairie species, as well as Tamarack, Eastern Red Cedar, Poison Sumac and pitcher plants. Particularly important to the Mitchell's Satyr is the presence of a healthy sedge community, particularly the sedge Carex stricta, which is the likely larval food plant for Mitchell's Satyr caterpillars. In addition to Mitchell's Satyr, prairie fens are also important habitat for other rare butterflies like the Powesheik Skipperling and other rare insects and plants.
Fens that meet the requirements of Mitchell's Satyr have probably always been relatively rare and local, making each one, extra important for the preservation of the rich biodiversity that occurs in them. Unfortunately humans have been destroying and degrading wetland habitats for centuries, and fens with their complex web of groundwater sources are especially prone to degradation. As these fens have disappeared off the landscape, so too has Mitchell's Satyr and now the species is one of the rarest butterflies in the world, with a tiny population almost entirely confined to Michigan.
Fortunately for Mitchell's Satyr they received endangered species protection when they were federally listed in 1992. This affords them some protection from habitat loss and degradation, as well as deterring some of the threat from collectors (sadly rare butterflies are especially valuable to certain types, who can't resist adding ultra-rare butterflies to their collections, even willing to pay huge costs to get them). In fact, it is believed that the last site in New Jersey may have succumbed to butterfly poachers, who can make big money from even a single specimen.
So anyway, Nikki and I travelled to a fen in Berrien County (at the southwestern edge of Michigan) that still has a healthy population of Mitchell's Satyr. Adult Mitchell's Satyr can only be see during their narrow flight period which typically occurs only during the last week in June and the first two weeks of July. So we scheduled our visit right in the middle of this period around the 4th of July. Although this seems to have been a late year for the start of the Mitchell's Satyr flight, we luckily arrived right for the beginning of it and we ended up seeing a total of about 6 Mitchell's Satyrs. They weren't very cooperative for photography but one did settle on a sedge for a few seconds, just enough time for me to snap one decent photograph (see above) which I have now made into the background on my cell phone! It was great getting to spend some time in this rare and endangered ecosystem (even if we did get bit up by deer flies and chiggers). To me the surviving prairie fens are the most interesting habitat in southern Michigan.