Starlings show considerable variation in egg mass among clutches. Mean clutch egg mass was highly repeatable for females, but few characteristics of females were found to relate to egg mass. Egg mass related weakly to female age, but female age only explained a small part of the variation. Hatchling mass was strongly correlated with egg mass, but body mass at 14 d of age was unrelated to egg mass. Nestling tarsus length at the same age was related to mean egg mass in one, but not another, year. Egg mass had no effect on hatchability or fledging success, although there was some evidence that brood reduction was more severe among broods hatching from small eggs. Females that had laid larger eggs were in better condition during incubation thus suggesting that high quality females are able to lay larger eggs and to maintain higher body reserves during incubation. This was supported by the observation that females laying smaller eggs were more likely to abandon their nests during incubation.

Imperial Eagles. Behav. Ecol. Sociobiol. 32: 259-263. and Calder6n, J. 1990. The Spanish Imperial Eagle Aquila adalberti in Dofiana National Park: a study of population dynamics. Biol. Conserv. 51:151-161. Green, R. E., Hirons, G. J. M. and Johnson, A. R. 1989. The origin of long-term cohort differences in the distribution of Greater Flamingos Phoenicopterus ruber roseus in winter. J. Anim. Ecol. 58: 543-555. Greenwood, P. J. 1980. Mating systems, philopatry and dispersal in birds and mammals. Anim. Behav. 28: 11401162. Hentzelman, D. S. 1975. Autumn hawk flight, the migrations in Eastern North America. Rutgers Univ. Press, New Jersey. Johnson, C. G. 1969. Migration and dispersal of insects by flight. Methuen, London. Johnson, M. L. and Gaines, M. S. 1990. Evolution of dispersal: theoretical models and empirical tests using birds and mammals. Annu. Rev. Ecol. Syst. 21: 449-480. Newton, I. and Marquiss, M. 1983. Dispersal of sparrowhawks between birthplace and breeding place. J. Anim. Ecol. 52: 463-477.

Results of a long-term study of the Willow Tit Parus montanus population in the birch region at Venabu, Ringebu (61?39'N, 10008'E) in Central Norway, are presented. After fledging, the juvenile Willow Tits were dependent on their parents for another 2-3 weeks. During that period, they developed their vocabulary, which was nearly complete before independence. The syntax and ontogeny of eight main vocalizations (including the song) are described and illustrated by spectrograms. Non-aggressive calls developed before those with an aggressive content, the latter being postponed to the end of the period of parental dependence, or immediately thereafter. This pattern is probably adaptive. For comparison, also the corresponding adult vocalizations are described and illustrated by spectrograms. Besides the main sounds, a special puretone note, which evidently is restricted to the Willow Tits at Venabu and maintained in the deme by learning, is described. It is suggested that subsong has an important function in the process of vocal development.

were usually successful in their supplanting attacks, but the dominance order between the two species was not absolute and the number of interspecific interactions were few. As emphasised by the authors, it is necessary to consider how applicable the results from birds held in captivity are to the natural situation. In this paper I present the results of interspecific encounters between five tit species visiting an outdoor feeder in central Norway. In general, the following social rank order was observed: Great Tit P. major > Blue Tit P. caeruleus > Marsh Tit P. palustris > Coal Tit > Willow Tit. The Coal Tits showed a statistically significant tendency to be dominant over the larger Willow Tits, although not in all cases. Nevertheless, it seems that the Coal Tit's status in the social hierarchy requires consideration in the current discussion on the interspecific competition for food and foraging sites among species belonging to the tit guild of the coniferous forest.

Relative growth of body parts (wing, culmen, tarsus) in young Snow Geese differed among years and among summer feeding areas only a few kilometers apart in the vicinity of the McConnell River, Northwest Territories, Canada. Gosling age was unknown at time of capture, so we expressed all differences in measured characteristics as a function of culmen length. This procedure may underestimate the magnitude of differences in growth with respect to age. Year and summer feeding area had large, independent effects on relative growth. Growth of primary feathers showed the greatest variation of measurable variables among feeding areas. We argue that the cause of most differences in relative growth was nutritional variation of vegetation. If goslings with retarded growth do not entirely catch up on fall staging areas, there may be lasting demographic effects.

The mating system of Kentish Plovers was studied in Hungary in 1988-91. Pairs renested together after clutch failure on 11 occasions. In addition, two males and one female changed mates (sequential polygyny and polyandry) between clutches. Biparental care lasted 5.9?5.9 (s.d.) d (n = 20) from hatching to desertion, usually by the female. The duration of biparental care was not related to the sex of the deserting parent, but male-deserted broods hatched earlier than female-deserted ones. In 5 out of 11 cases when pairs renested together, they moved between breeding sites (11.8?5.8 (s.d.) km), as did all three birds who changed mates (10, 24 and 24 km). These recorded distances suggest that the low reported frequency of mate change may be more a reflection of the high level of breeding dispersal than of the rarity of mate change.

has been stronger in the western part of its European breeding range than in the eastern. Using recent developments of capture-recapture methods to estimate survival rates, including in particular a study of relationships with environmental variables and a comparison between populations, this paper examines changes in survival rates of some European populations of the White Stork. Survival rates of all populations wintering in the Sahelian zone were positively linked to the amount of rainfall in their wintering area. However, the survival rate of the population wintering in East Africa was not significantly related to the amount of rainfall there. No significant effect of the amount of rainfall in the breeding area on survival rate was observed. Differences in survival rates were observed within western populations and between the western and eastern populations. An effect of age was only significant in the Alsacian population. No significant difference in survival rates was found between male and female storks.

An index of condition was developed for wild Red Grouse chicks aged 10-30 days. This was derived from the difference between the observed weight and that expected from the chick's age, or stage of feather development. To measure it, the chicks needed to be caught only once. Variations in condition among different broods of wild chicks were greater than variations among broods of captive chicks in the same years, probably because the wild chicks' environment was harsher and more variable. Within years, the condition of wild chicks was not related to their brood size. Among years, mean condition was correlated both with breeding success and with the biomass of green heather food available in spring. This was because the chicks' condition and survival were poor for two years following an episode of severe weather damage to the heather.