Using data from the field and the literature on 67 species of birds, we analyzed intraclutch variation in egg size, especially the deviation of the last egg from the clutch mean (D). Values of D are closer to zero in precocial than in altricial species; D is negatively correlated with body size in interspecific comparisons, i.e. large birds, including precocial species, lay small final eggs; and D is higher in open-nesting passerines (on average D = +3.56%, 17 species) than in hole-nesting species (on average D = -0.05%, 13 species). Within populations of birds, a negative relationship exists between D and clutch size, particularly in species that have a generally low value of D. The results support the view that intraclutch variation in egg size has an ultimate, adaptive value. We suggest that birds adopting the "brood-reduction strategy" have a small final egg, particularly those birds with large clutches, whereas birds adopting the "brood-survival strategy" have a relatively large final egg, particularly those birds with large clutches.

We studied the frequency of partial albinism amongst hooded crows in Norway, mostly in a population at Trondheim. A total of 3461 birds were collected from the field. About 5% of fledged young showed albinoid markings on their third right‐hand primary; the frequency decreased to 2% among yearling birds and to only 1% among birds that had acquired their adult plumage. No significant difference was found in relation to sex. The partially albinoid birds were typically small‐sized, both as regards their bone structure (ulna, tibia, tarsus) and feathers (wing, tail). Their feathers bore more defective markings than those of birds of normal plumage coloration. A study of the plumage of preserved specimens of hooded crows in the collections of Natural History museums in Norway also indicated that a differential mortality takes place in the wild, such albinoid birds disappearing rapidly from the population. Experimental interchanges of eggs and hatchlings between nests indicated that the occurrence of partial albinism may be related to the feeding conditions during the nestling stage, rather than to any genetical differences. It is not known, however, whether the former was due to starvation, to an unbalanced diet, or to eating poisonous food.

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. , J. 1985. Variation in egg size of the Hooded Crow Corvus corone cornix. -Ornis Scand. 16: 38-44.Variation in egg size of a population of the Hooded Crow Corvus corone cornix was studied at Trondheim in Central Norway, during the period 1979-1982. No significant differences in egg volume were found neither from one year to another nor within different sized clutches, nor with laying date. The hatchability of small sized eggs and of eggs laid late in the laying order was lower than that of large sized eggs and of eggs laid early in the laying order. For all clutch sizes, a decrease in egg volume was found with increasing order of laying. All the last laid eggs (n = 39) had a smaller volume than the mean for the same clutch. The relative size of the first laid eggs (deviation from the mean for the same clutch) decreased with increasing clutch size. A significant positive correlation existed between the body weight of the hatchling and the volume of the egg from which it hatched. Both male and female hatchlings hatched from eggs of similar size, and had roughly the same body weights at hatching.

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. Rofstad, G. 1988. The effects of weather on the morphology of nestling Hooded Crows Corvus corone cornix. -Ornis Scand. 19: 27-30.Weather conditions (amount of precipitation and ambient temperature) during the nestling period were found to affect the dimensions at fledging of several morphological characters of nestling Hooded Crows. Morphological characters that develop rapidly over a relatively short period were more sensitive to weather conditions than those that develop gradually throughout the nestling period. The effect of wheather conditions on nestling growth is thought to be mainly a result of a decrease in food supply during periods of wet and cold weather. The annual differences noted in the size of nestling Hooded Crows may be explicable in terms of differences in the weather conditions that prevailed during the nestling period.