Trichostrongylus tenuis eggs were counted in faeces from individually marked wild red grouse for 8 years. Egg counts varied seasonally and annually. In some years, a sudden increase in mid-April was consistent with delayed maturation of larvae which had overwintered in the birds in a hypobiotic state. A more gradual increase in summer was probably due to uninterrupted maturation of larvae ingested then. Despite 30-fold year-to-year variation in mean egg counts, relative differences in egg counts among known individuals within years tended to persist across years. Rainfall in previous summers explained much of the year-to-year variation in egg counts, probably because parasite recruitment was greatest during wet summers. Grouse density was only weakly related to worm egg counts. The data were not consistent with the hypothesis that the cyclic-type population fluctuation in red grouse numbers observed at the time of this study was caused by the parasites.

No abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Wiley and Nordic Society Oikos are collaborating with JSTOR to digitize, preserve and extend access to Ornis Scandinavica. R. 1990. Plant growth and nitrogen metabolism of Red Grouse Lagopus lagopus scoticus in spring. -Ornis Scand. 21: 115-121.Annual variations in the total nitrogen content of Red Grouse faeces in spring reflected variations in the growth and N content of their main food, ling heather Calluna vulgaris. The N metabolism of birds eating low-protein, high-polyphenol diets such as heather is poorly understood. This was described by analysing the N in faeces into six chemical fractions. Variation in these fractions was partitioned statistically into principal components on the working assumption that each component reflected a distinct metabolic process. Annual variations in the first principal component were related to the amount of overwinter dieback in the heather but not to the heather's total N content or growth. Variations in the second were closely related to the total N content and growth of heather but not to overwinter dieback. Protein appeared to be in short supply in the birds' diet. However, annual variations in the first principal component of faecal N occurred independently of the total N contents of food and faeces. Therefore the total N content of the birds' diet probably did not reflect its nutritive value and total faecal N was probably not a reliable index of dietary quality. No measured aspect of N metabolism was related to the birds' breeding success.

No abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.