Bright lighting for birds particularly white birds is hard but it can be done.
Best method is to use manual exposure. Using any auto mode and the camera will almost always find a way to screw you, especially on those white birds.
You will need to expose for the white birds and don't worry about the background going dark. A dark background makes white birds pop out better anyway.
But of course early morning or early evening light is generally better for birds. Still go with manual exposure though.

My 'somewhat limited experience' is that if they are using your images for advertising they will want a digital image that can be manipulated to their own specifications by their own people. I also think the price for the image(s) is going to be somewhat determined by the size of the credit union, your professional history and the number of the images they are interested in. If it’s your first sale of this type, do you want to make a killing and risk not making the sale or are you more interested in starting to build a reputation that could lead to additional sales. I’d probably determine the minimum price I’d be will to accept, add some room to negotiate and then sit down with the client and start talking. Remember, they are going to use your work to make money, so don’t sell yourself short. Hope this helps at least a bit. Good Luck!!!!

I print & sell my 13x19 (Museum Quality Paper) individual signed prints for $135 ea. However, since your selling to a business.. I would strongly suggest registering the print(s) with the US Copyright office. www.copyright.gov It's only $35 per submission NOT per photo.. hence you can register 5,10 or so per reg. It is a very good way to protect yourself from a 3rd party using your work without your permission... Perhaps your question to this group should be. What is the value of your work that is used for commercial use if you sell with or without the copyrights?