Gun suggestions?

Hi Airgun nation,
I have been Internet researching air guns all day and am more confused now than when I started.
I grew up with my Daisy lever action, moved on to a Crossman 880 then a Hornet break-barrel.
I have lots of experience with shotguns and powder rifles.
I now find I have the need for an air gun that can reach out 150 yards to discourage the birds that 
use by moored boat as their kitchen and bathroom. It doesn't need to be lethal at that distance but 
enough to make the birds move along. I can lob a 177 with my springer to the boat but it gets there
with the authority of a raindrop after I aim fifty feet over.
So--- I'm hoping for advise on what would best suit my needs.
I would like to keep it under 1K and already have scuba tanks and access to a compressor.
In a perfect world quieter would be better than louder.
Any suggestion will be appreciated.
Thanx,
CB 
 
Faced with the problem of Canada geese pooping on my aluminum dock I have resorted to "pinging" the dock using a 25 cal Marauder and JB 25.4 gr pellets. The end of the dock is 140 yards from the house. At that distance I can hit one of the two inch upright posts ca one third of the time. When a pellet lands on the dock surface the resulting ping causes the geese to vamoose and they usually stay away for a month or so.
 
Thanx Tony and Ezerhoden14,
I like the suggestion of a Marauder. In looking into the Marauder I ran across the Armada which is supposedly based on the Marauder. I have to admit the looks kinda hooked me. As I tried to justify the much higher price tag the only functional difference I could find was more versatility in the stock and a picatiny rail that i don't really need. Am I missing something? It just seems like a big difference in price just for the stock and a rail. Ezerhoden, great idea putting up a metal plate. Less chance of putting a hole in the boat.
 
Thanx for the input everyone.
I'm looking right now at a giant cormorant sneering at me while pooping on my outboard, that says it's time for a decision.
I'm going to go with function over form an get the Marauder .25, spend the extra money on a quality scope and start welding up the metal plate idea.
My last request (yeah right) would be some suggestions on a list of specific ammos to start with and a decent chrono.
Time for me to start reading up on the tuning process.