Hi Oksana and welcome to the forum:
Honestly, much depends on the specific conditions at the time. What precisely do you mean when you say you didn't get a clear shot? Perhaps upload a sample image and you exposure (EXIF) data so it gives us something to work with.
All that said, if the birds are not actively in flight, then the thing you most likely want to control is the focus - getting the subjects to stand out from the background, for which I would recommend Av Mode, and set the ISO at Auto.
Getting the birds in focus is critical and you need to be careful of using all points, this is where Animal Eye focus would come in handy, as it should lock focus on one of the birds. While you are doing so, just keep an eye on the shutter speed to make sure it is dropping below 1/250sec.
This is all without looking at the specific issues of your images, we can be more specific if you can provide one or more samples and especially with the EXIF data.
cheers, TREVOR
"The Amount of Misery expands to fill the space available"
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
