Karlskaret fan, with a radius of less than 11/2 km and dominated by debris‐flow conglomerates, is one of numerous alluvial fans built out from the fault margins of Hornelen Basin (Devonian, Norway). The fan body is more than 170 m thick proximally, consists of four main coarsening‐upwards segments and thins distally by a rising of its base and by a vigorous interfingering with very fine‐grained sediments originating from an adjacent, impinging floodbasin system. Within the entire fan body, and within individual lobes, is a proximal‐distal (and vertical) facies change from sheet‐like, polymodal debris‐flow conglomerates through matrix‐rich conglomerates that are commonly distorted by loading, slumping and faulting, to remarkably sheet‐like, matrix‐rich granule sandstone of subaqueous debris‐flow origin. Because the alluvial fan prograded into an actively aggrading floodbasin the primary fanglomerates, themselves having been subject to some sorting on the fan surface, incorporated large quantitites of very fine sediments. This inclusion of fines, effectively a textural inversion on the lower fan reaches, frequently led to remobilization and resedimentation of material beyond the fan toe. Anomalous maximum particle size/bed thickness relationships and a variety of graded textures within these resedimented beds suggest deposition in lacustrine areas of the adjacent floodbasin.

Summary1. The incubation-limitation hypothesis states that clutch size in shorebirds is constrained by the ability to incubate more than four eggs successfully. In order to test predictions from this hypothesis, clutches of northern lapwings ( Vanellus vanellus ) were here experimentally increased and reduced by one egg at the onset of incubation. Parental behaviour, incubation time, hatching synchrony, egg viability, hatching success and body condition of hatchlings was compared with unmanipulated clutches. 2. Nest desertion and egg breakage was not observed in any of the experimental nests, showing that clutch enlargement did not alter the parental behaviour adversely. 3. There were no differences among the experimental groups in male and female attentiveness, but the total nest attentiveness was lower in reduced clutches than in the other clutch sizes; nor did the parents' frequency of nest visits differ between clutch sizes. 4. Enlarged clutches were incubated longer than controls and reduced clutches. There were, however, no significant differences among clutch sizes in partial or total clutch predation rates. Hatchability of the eggs (proportion of eggs hatching of those present in nests at the end of incubation) was marginally lower in the enlarged clutches (92·5% vs. 100% in the two other groups). 5. Contrary to predicted, hatching success was highest in enlarged clutches. The numbers of hatched eggs calculated from Mayfield estimates of daily nest and egg survival rates were 0·93, 2·10 and 3·14 in three-, four-and five-egg clutches, respectively. 6. When controlling for egg volume, mean body mass of newly hatched chicks was lower in clutches with five eggs than in other nests. 7. We suggest that the lowered body condition of chicks could outweigh the benefits of laying five instead of four eggs in northern lapwings. Future studies of the selective mechanisms of clutch size in shorebirds should not only focus on the number of young that hatch, but also their quality.

Previous studies of sex roles in the polygynous Northern Lapwing Vanellus vanellus have shown that males incubate less than females, perhaps suggesting that sexual selection is important in shaping the parental behaviour of this species. The purpose of this study was to (1) examine for the first time the possibility that males compensate for low diurnal nest attentiveness by increasing their nocturnal assistance and (2) evaluate the hypotheses that sexual selection and individual breeding quality determines incubation behaviour in lapwings. Males were never found incubating at night in 19 nests, although median diurnal male attentiveness was 15.3% in 16 of the same pairs. Nor were there any differences among monogamous and polygynous males in the time spent in four categories of behaviour (incubation, guarding, maintenance and mating activities). The time males spent in mating and incubation behaviours was weakly negatively correlated, and the time spent incubating varied considerably among males (0-74%). Further, female body condition was positively related with male nest attentiveness and there was a negative relationship between nest attentiveness and date of arrival to the study area in monogamous, but not in polygynous, males. We argue that sexual selection could not alone explain all sides of Northern Lapwing incubation, and suggest that individual differences in breeding quality may also be important.