Destroying nests make chickens weaker lowering their techs. If team work coop then nests can killed fast and there isnt problems with chickens.
If you want stronger chickens just don't destroy they nests. Then you face with blobers, powerfull long range arthy like bertha (chicken spire or something like that), mass air units.
If you want play harder game then try just random maps in hard or suicidal. Not only special chickens maps. :)