Nectar sources on the Vischer Ferry Cout

[Michael Gochfeld]

I keep tabs on the nectar sources used by each butterfly encountered. 
Sometimes it's tedious,but most of the time not.  In many places Common 
Milkweed (A. syriaca) is a wonderful attractant for butterflies, and 
once at Ward Pound Ridge (Westchester County, NY), Guy Tudor and I 
observed six skippers of five species, on a single Milkweed head. 

Dogbanes are likewise very attractive in some areas. Dogbane is abundant 
in the Mohawk floodplain and was beginning to flower. I have checked it 
hopefully year after year and found virtually nothing on it. This year 
there was one Red Admiral on Dogbane. 

On the first Lakehurst NJ, Count we had dozens of Hairstreaks nectaring 
on Milkweed, a phenomenon not repeated in subsequent years. 

On the Vischer Ferry Count last week, Common Milkweed was blooming 
profusely, and there were many Honeybees and some Bumblebees on them, 
but virtually NO butterflies AT ALL.

Various clovers, paricularly Red Clover is another popular nectar source
The single Bronze Copper was on White Clover (let me know if I need to 
provide the scientific name). Eastern Tailed Blues were on Red and 
Alsike Clovers. 

Most Red Admirals were just flying through, but 53 were nectaring 
including 1 on a Thirslte,8 on Red Clover and one on Dogbane 
(aforementioned).  However, 43 were on Canada Thistle (Cirsium arvense). 

Actually when I tallied the counts that I made,  65% of bees  counted 
(there were more, of course) were on Canada Thistle and 64% of butterfly 
records were on Canada Thistle. 

Interestingly virtually none of the skippers were on Canada Thistle, 
although I have often seen skippers and Cabbages on this species. 
Moreover, the next day in another yard, there were three species of 
Skippers on Canada Thistle, and Ladies and Great Spangled Fritillaries 
clearly preferred it to the Buddleia. 

Obviously I looked for patches of Canada Thistle to find the 
butterflies, so from a statistical view I over-sampled that source. But 
I also carefully checked EVERY one of the hundreds of milkweed plants 
and carefully checked MANY of the thousands of Dogbanes, and and covered 
many areas with clovers.  

This is not a novel observation for me.  I have often found that Canada 
Thistle is preferred during the few weeks that it is in bloom. 

Now for the problem.  As most of you know Canada Thistle is classified 
as a noxious weed.  Here is a sampling from the web: 
==================
Canada thistle is declared a "noxious weed" throughout the U.S. and has 
long  been recognized as a major agricultural pest, costing tens of 
millions of dollars in  direct crop losses annually and additional 
millions costs for control. Only recently   have the harmful impacts of 
Canada thistle to native species and natural ecosystems received notable 
attention. 


        HABITAT IN THE UNITED STATES: Canada thistle grows in barrens, 
glades,  meadows, prairies, fields, pastures, and waste places. It does 
best in disturbed  upland areas but also invades wet areas with 
fluctuating water levels such as streambank sedge meadows and wet 
prairies. 

BACKGROUND: Canada thistle was introduced to the United States, probably
by accident, in the early 1600s and, by 1954, had been declared a 
noxious weed in forty three states. In Canada and the U.S., it is 
considered one of the most tenacious and economically important 
agricultural weeds, but only in recent years has it been recognized as a 
problem in natural areas. 
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