From the Field - Mariton Wildlife Sanctuary

Wind Power and Bird Fatalities

"Nocturnal Bird Migration Over an Appalachian Ridge at a Proposed Wind Power Project" is a research paper published in The Wildlife Society Bulletin October 2006.  The authors (Mabee et. al.) studied night migration along an Allegheny Frontline in West Virginia in the fall of 2003.  They used an equipment van with a roof-mounted marine radar antenna to monitor flight direction, altitude, passage rates and groundspeeds.

I was interested by several things in this paper.  For instance, I learned that resident raptors were the main fatalities at older wind powered units in the U.S.  Because of this, most modern facilities study the behavior of diurnal species when planning the layout of the windmills.  This is great.

However, there are all sorts of other birds (and bats) that use the same ridgelines at night and at different seasons of the year.  In fact, more birds migrate at night than during the day.  The authors point out that much more research needs to be done in the planning of wind powered units.  For instance, this study was conducted for 6 weeks in the fall, during peak passerine (songbird) migration, however, "most bat fatalities at wind power developments appear to occur between approximately mid-July and late September (Johnson 2004)."  I also learned that songbirds migrate at much lower altitudes than waterfowl or shorebirds.  Their research corresponded with previous research that most songbirds migrate below 600 meters (above ground level).

A few more interesting points:  Most of nocturnal use occurred from an hour after sunlight until 2:00 a.m.  They observed relatively large flights of birds on about a quarter of the nights monitored.  The mean flight altitudes were above the proposed turbine heights, however, there were 5 nights when the mean flight altitudes fell to 200-300 meters.  Birds did not seem to use the Allegheny Frontline to migrate along; rather most of their observations had birds flying across instead of parallel to the ridgeline.  The authors felt nightly variations would be explained by weather and even the species of birds migrating.  Obviously, spring migrations weren't studied in this research, but should be in the future.

I think the important point made by this research is that this equipment is capable of detecting night bird migration; and that with more baseline data humans will be able to predict where most bird strikes are likely to occur before the wind turbines are constructed.

Autumn Leaves

I finally raked up the last load of leaves for the season!  This year, I moved a total of 29 pick-up loads of leaves, which is about average.  I started raking as soon as the leaves started falling.  Over the years, I have found that if you rake a day a week throughout the fall, the leaves don't get embedded in the grass, and they are easier to rake.  It is also a lot easier moving that many loads over a two month period as opposed to a two week period.

I know that I am considered old-fashioned because I still use a rake and haven't switched to a gas-powered blower.  Truth is:  I am just as fast with the rake as the blower.  The difference is that it is more physical to use the rake.  (I figure that helps keep me in shape.)  Plus, I don't have to listen to the whine of a two-cycle engine, or inhale the fumes.

My leaf pile resembles a mountain about this time of year.  But I will turn it regularly with the front end loader and the leaves will compost nicely.  I don't use the soil from the compost anymore though.  About one quarter of the leaves from the yard are from walnut trees.  These trees produce juglone which is a compound that inhibits the germination of other plants.  There is some juglone in the leaves, at least enough to discourage the growth of everything except for weeds.  Trust me on this, I found out the hard way.   

Bluebird Activity

There has been a lot of bluebird activity lately.  Maureen watched a group of four bluebirds investigating the nest boxes in the yard on Sunday.  On Tuesday, I watched a group of four females and one male investigating boxes in one of the meadows.

They actually took turns checking out the boxes, while the rest of the group sat on top, or perched on nearby vegetation.  Is it one of the groups that nested here this summer?  Or is it a family group that flew here from another locale for the winter?  Are they looking for someplace to nest in the spring?  Or are they looking for shelter from a winter storm or a bone-chilling night?

I honestly don't know; but we sure enjoyed watching them.  Something about their color, their bubbling song, even the way they fly is cheerfully infectious.