[CT Birds] Moorhen mystery

Anthony Zemba Anthony.Zemba at gza.com
Wed Jul 20 16:05:05 EDT 2011

Hi Paul:

South of Newberry Road, the system is dominated by what is referred to as a PEM1E System - a Palustrine Emergent Persistent Seasonally Flooded/saturated system using the Cowardin (1979) Classification System.  By definition of this classification system The word "Palustrine" refers to a non-tidal wetland "dominated by trees, shrubs, emergents, mosses or lichens, and all such wetlands that occur in tidal areas where salinity due to ocean derived salts is below 0.5 ppt"... (there are some other criteria but not really relevant to this discussion right now. The class name in the hierarchy ("EM"= emergent) "includes wetlands characterized by erect, rooted, herbaceous hydrophytes, excluding mosses and lichens. This vegetation is present for most of the growing season in most years". These wetlands are usually dominated by perennial plants. The subclass designation (1 = Persistent) means that the wetland is dominated by species that "normally remain standing at least until the beginning of the next growing season". The "E" in the designation denotes the water regime as Seasonally Flooded/Saturated, defined as "Surface water is present for extended periods especially early in the growing season and when surface water is absent, substrate remains saturated near the surface for much of the growing season".

North of Newberry Road the system is predominantly an interspersed PEM1/SS1F or a Palustrine Emergent Persistent (PEM1)/ Scrub shrub broad leaved deciduous (PSS1) semi-permanently flooded system (F). The scrub-shrub cover type "includes areas dominated by woody vegetation less than 6 m (20 feet) tall. The species include true shrubs, young trees (saplings), and trees or shrubs that are small or stunted because of environmental conditions". The Subclass designation of Broad-Leaved Deciduous refers to "Woody angiosperms (trees or shrubs) with relatively wide, flat leaves that are shed during the cold or dry season".  The water regime is denoted as Semi-permanently flooded which is defined as "Surface water persists throughout the growing season in most years. When surface water is absent, the water table is usually at or very near the land's surface".

Now, knowing the above, one can compare/contrast that description to the preferred habitat of the Common Moorhen as described by Greij (1994) which is as follows: "dense stands of emergents with openings approximating a nearly equal interspersion of cover and open water".

One can hypothesize that the wetland cover type may no longer be suitable for attracting breeding Common Moorhens. He cited an extensive study done by others at an Ohio wetland of 5,188 ha. In that study the researchers found that the highest densities of moorhens occurred in deep marshes with robust growth of emergents and a nearly equal interspersion of cover to open water, while lowest nesting densities occurred in wetlands with non-persistent emergent wetland vegetation; mixtures of scrub/shrub and persistent emergent vegetation (= Station 43); and seasonally flooded or un-diked, intermittently exposed wetlands with a high ratio of open water to persistent emergent vegetation.

In a nutshell, the wetland cover type may have become unsuitable for Moorhens over time via the natural process of succession at Station 43 and within the interconnected wetland system.

Anthony Zemba CHMM
Certified Ecologist / Soil Scientist
GZA GeoEnvironmental, Inc.

655 Winding Brook Drive
Suite 402
Glastonbury, CT 06033

1350 Main Street
Springfield, MA 01103

860-966-5888 (cell)
413-732-1249 (fax)
anthony.zemba at gza.com

-----Original Message-----
From: ctbirds-bounces at lists.ctbirding.org [mailto:ctbirds-bounces at lists.ctbirding.org] On Behalf Of Paul Desjardins
Sent: Monday, July 18, 2011 5:36 PM
To: ctbirds at lists.ctbirding.org
Subject: [CT Birds] Moorhen mystery

i was wondering if anyone out there could shed some light on the disappearance of Common Moorhens at stn 43
South Windsor. At one time they were very reliable with up to 12 being the maximum number number seen at once.
The last time i noted the species here was on August 11th 1987 when i noted one bird except one years later which
i took to be a transit. The habitat seems not to have changed much over the years so this is a mystery to me. Any
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