John and all--
        This is a good question. A decline in numbers of RBM observed along the
Ohio lakefront seems evident over recent years. Not reliably to folks
like me, as we don't get a chance to observe this area all that often,
but the testimony of John and others who do seems significant.
        ODOW surveys lump the merganser species seen on Lake Erie, but hooded
mergansers are in relatively low numbers, and common mergansers tend to
reach peak numbers much later than red-breasteds, being far more likely
in mid-winter, mostly outside hunting season.  These aerial surveys,
aimed as they are at easily huntable birds, take place quite close to
shore, at distances closer than we see red-breasted mergs passing by
farther offshore. So there are two biases in these data.
        So, one factor might be proximity to shore, where nearly all reported
observations are made from land. Have RBMs increasingly moved and
foraged out of sight far out into the Lake, maybe because of a change in
food sources? It might be worth finding out if any systematic surveys
have been made way out there...there has been speculation, for example,
that certain species like red-necked grebes can winter far out in
mid-Lake, well out of sight of observers.
        As John suggests, another factor might be a displacement to other Great
Lakes sites, in response to food sources or temperature changes, and so
on. No doubt, even based on the scanty information available, RBMs were
a lot scarcer for NE Ohio observers 50-100 years ago--see Peterjohn
(2001:102-104) for data, as well as for questions about how well we are
able to count them. John mentions that November has been the best time
to see RBM movements, and that the CBC period (mostly mid-Dec to early
Jan) comes after most of them have departed....where are they later? Are
they simply moving there earlier than in recent years, without spending
time along the southern shore of Lake Erie?
Bill Whan
Columbus


John Pogacnik wrote:
> I have a heard a lot of people discussing the decline in red-breasted
> merganser numbers over the years.  One of the most amazing sights I
> have ever had a chance to witness was watching approximately 250,000
> red-breasted mergansers pass by the Vermilion area.  The following
> year ODOW surveys confirmed close to that number.  It was stated that
> the majority of the red-breasted merganser population was using Lake
> Erie as a staging area.  What happened?>
>
> Those sightings were during the 1980's.  Since that time it seems
> that there has been a steady decline in red-breasted merganser
> numbers on Lake Erie.  In the early 1990's I remember seeing flocks
> that probably exceeded 100,000 birds.  November was the best time to
> see this and the Huron-Vermilion area was the best location.  Last
> weekend I was at Huron and didn't see a single red-breasted
> merganser.  There are decent flocks around especially east of
> Cleveland, but most of these flocks are 5,000 or less.  Where are the
> bigger flocks?>
>
> Should we be concerned with this decline.  Are the red-breasted
> merganser flocks spreading out over the Great Lakes, are they passing
> us by, or is there a major decline?  As far as waterfowl surveys go,
> they seem to lump all of the mergansers since thay are not as
> important to hunters.  Vic Fazio had numbers of Ohio red-breasted
> mergansers through the years.  Hopefully he is out there and can post
> them.  There appears to be something going on here.  Were the 1980's
> unusual that for some reason there was a massive increase in
> mergansers.  Maybe there is something to this.  If you go to the
> Christmas Bird Count website and create a graph for red-breasted
> merganser, from 1960- present for the United States, there is a large
> spike in numbers from about 1982-1993  Before and after the spike,
> the graph is pretty level.  Interestingly, if you create a graph back
> to the 1930's, there was a shorter spike from approximately
> 1937-1942.  Maybe the question should be, what caused the spike in
> numbers in the 1940's and 1980's.  Also how do the last few years
> numbers locally compare with numbers in the past outside of the
> peeks.  The Christmas Bird Count data is limited in use for Ohio
> since most of the mergansers have departed by the time of the counts.
> Although data shows there has been an increase over the last few
> years in Ohio.>
>
> If you want to play with the Christmas count graphs, here is the
> link.>
> http://audubon2.org/cbchist/graph.html>
> John Pogacnik





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