I've recently discovered a phenomenon which I call the blue zone. After sunset, a varying amount of minutes depending I am guessing on where you are in the world and what date, the sky when photographed with a longish exposure will go a deep shade of blue. I imagine that many photographers have known about this for a long time, but as I say it was a new one on me. It is no good for birds obviously, however for landscapes it is excellent. You will need a tripod, or be able to find a suitable perch for your camera which will keep it still (I often use my bag to create a level surface and simply rest it on that), and ideally a cable release. Using either a long exposure or the bulb feature where you can keep the shutter open indefinitely, the trick is just to experiment with different lengths of exposure until you draw out the blue - be warned though, the light only stays like this for a matter of minutes so you don't get many chances. Ensure you have done all your framing and so on well before you get to the appointed time!
Here are a couple of the Hungarian Parliament building on the Danube at Budapest, as well as one of Valletta in Malta. Well lit impressive buildings are the ideal subjects for these types of images. Just bird photos? Well, nearly! The Danube photos are 6 second exposures at f11 and f13, and the one from Malta is at 5 seconds at f11, all using ISO 50. The reason for the long exposures was to soften the water but it also seems to make the blues more intense.