I take a more simplistic view.  All of the species being mentioned ( Ring billed Gulls, Common Tern, cormorants, herons) are all native species.  Let them come to their own balance.  I was opposed to shooting Great Horned Owls and Black Crowned Night Herons when they were identified as a possible cause for Common Tern decline in Vermont.  Species have ebbs and falls.  Let native species find their own carrying capacity.  The environment changes and, therefore, the carrying capacity for a species changes.  I find it incontiousable that we go in and oil eggs or shoot cormorants or gulls.  Would we poison House Wrens because we find they are "responsible" for bluebird/phoebe declines or some other megafauna?  If someone convinces me that cormorants are increasing because of some human perturbation of our environment, I might feel differntly.
 
I questioned the efforts made to enourage Bald Eagle nesting in Vermont.  Historical records indicate that they were not a regular breeding specis in the state.  Yet, they attracted a great deal of interest and attention.  We need to look carefully, in my opinion, what species we feel need to be helped at the expense of others.
 
Bill Barnard
Northfield, VT