Slitere National Park area is occupied by swampy forests. Numerous small bogs in the marshy depressions form an open landscape, which is very suitable for black grouse. The amount of berries is very important. It seems that also the fact that in the territory of SNP bird hunting is banned for thirty years is important - this ensure calm environment for black grouse to mate. These and probably many other factors determine that the largest grouse lek in Slitere National Park is also the largest in Latvia, Baltic States and possibly in Europe. Here in one lek counted 66 black grouse males.To Grouse lek males fly long distances. Each male occupies its territory. The most valuable areas are placed at the center of the lek. Here are lekking most experienced and strongest males. Blackcocks show off in front of the females. When the lekking has achieved its peak, greyhens display at the lek and choose a male to mate with. Apparently, when they have arrived the intensity of the lekking grows. Males strike against one another with breasts, jumps into the air and hiss loudly. At first female lands at the periphery of the lek, but then goes to the center, where she finds herself a pleasant partner. In silent and calm mornings loud rookoing (mating call) can be heard far away. Grouse males are dressed particularly splendid. Black blue feathers are contrasting with bright white. Grouse males 'eyebrows' acquires very particular red tone. Unlike the males, females are dressed very simple and yet they are precisely the ones choosing.