Friday, July 27, 2012

New Habitats and a Visit to County Farm Park

One of my interests has always been how species move into areas when habitats open up that didn't exist there before. Back in my younger days as a college student and for several years thereafter, I studied solitary wasps in the families Pompilidae (Spider Wasps) and Sphecidae (Sand wasps). While many of the species in those familes like sandy habitats, they are also very good at colonizing new sandy patches that open up due to anthropogenic activities. Likewise, there are several species of Odonata that take advantage of newly-created wetlands. Anthropogenically influenced landscapes have probably been responsible for the spread of several species across North America, and that fact alone make it more difficult to assign blame to climate change for the spread of certain species. The US Interstate system provides long continuous swaths of habitat that has allowed the movement of insects and plants to spread at a far great rate than they would have if those corridors did not exist. There are examples of many species rapidly declining after the 1950s, which coincides with the completion of the Interstate Highway System (as well as well as the use of DDT, etc.). There are also more examples of species rapidly expanding in their range after the 1950s.

However, we can improve the quality of urban and suburban riparian habitats, and wetland mitigation projects and water runoff retention ponds are two such ways. Another is to re-engineer old channelized streams and slow them down to reduce siltation and improve water retention in the drainage area.

In terms of Odonates, we can count on seeing a few pioneer species when a new wetland is created. Obviously, the first species that comes to mind is the Eastern Forktail, Ischnura verticalis. Second would be the Common Green Darner, Anax junius, as well as various species of skimmers (Libellulidae). Eastern forktails are perhaps the most ubiquitous odes that I can think of in Eastern North America.

So, back to my original reason for this post. Late in the day, I walked over to Washtenaw County Farm Park, which is less than a half-mile from my house. I wanted to check out the Mallet's Creek Restoration and Wetland Project, which is managed by Washtenaw Co. Work started on this in fall 2011, and has continued into early in the summer. One of the objects was to change the waterflow of Mallet's Creek so that it no longer acts like a typical flash-flooding urban stream. The second was to reduce siltation, and slow the water that goes into the city stormwater drains from around County Farm Park (CFP). The one feature that has been lacking at CFP has been any sort of lentic wetland. This project created several swales and small ponds that are looking fairly good, even though we are going through a drought. CFP is now becoming a more diverse riparian environment, and my hope is to monitor the procession of Odonata that appear in the new habitat.

Last night, I encountered dozens of Eastern Forktails, one Blue Dasher (Pachydiplax longipennis, three Common Green Darners, and several Common Bluets (Enallagma civile). The darners were patrolling two deeper ponds, and often hovered right in front of me. I didn't have my DSLR with me for photography, but I did have my little pocket Sony camera, and took some photos. I am pretty ceratin that if I went there during midday, I would encounter the vagrant Pantalas and Trameas. I will return another time in early August and see what is flying. Next year, I expect to see a few more species at the new wetlands, and perhaps some stream species will take hold, too.

Well-planned reconstructions such as the one at Mallet's Creek are important to regaining healthy aquatic environments in suburban areas. Aside from the improved aesthetic appeal at CFP, the new riparian environment will benefit wildlife and provide new habitats to explore.

Friday, July 13, 2012

18,433 Odonata Nymphs!

That's how many nymphs (larvae) were in samples from about 15 years of ecological sampling from Earl Werner's projects at the Edwin S. George Preserve (ESGR) in Livingston County, MI. The ESGR has been owned since the 1930s by the University of Michigan, and has been the site of many long-term projects. We recently received all of Werner's samples, and the contents of each jar is cataloged in a Filemaker Pro database. I did a search for Odonata, and found over 18,000 nymphs of Anisoptera and Zygoptera, most of which have been identified to species. That is a tremendous amount of data from just one small area.

The larva shown here is a Swamp Darner, Epiaeschna heros. There are 19 records of this species in the ESGR data, and all are from early May to late July. This particular specimen is from sample ESGR-2005.107, on June 15, 2005. It's obviously a last-instar specimen, looking quite ready to emerge at any time. This tells me that E. heros does indeed overwinter as a larva in the Southern Lower Peninsula. I am sure we will get more useful Ode data in the near future from the ESGR collection. The white blobs on the prothorax are water mites.