The Genetics and Demography of a High and Low Density of Red Grouse Lagopus L. scoticus

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Abstract
High and low densities of red grouse are compared for food quality, demography and genetic variation. For 3 yr the mean territory size was smaller, and the breeding density and brood size were higher on the high-density population. The breeding success (young/hen) and production (young/adult) fell on both areas, but breeding still remained higher in the high density group. There was no correlation between the nutrient content of the grouses'' main food, and mean territory size, breeding density, breeding success of production. There were more heterozygote, and fewer homozygote, chicks in the higher density population for 3 yr. Broods of predominately heterozygote chicks tended to be larger. More lightly colored chicks were found in the higher density population. Lightly colored broods were generally larger than darker ones. The fall in breeding successs and production, was not correlated with changes in phenotypic frequencies, but was correlated with the frequency of the NgM allele. The fall in breeding production was probably caused by dispersal from the high-density population.