Timing and duration of moult in three populations of Purple Sandpipers Calidris maritima with different moult/migration patterns

Timing and duration of primary moult in three populations of Purple Sandpipers Calidris maritima were described and discussed in relation to the birds’ need to complete moult before the onset of winter, when resources are required for survival. We predicted that moult would be completed earlier by birds wintering at higher latitudes. The south Norwegian breeding population, which moults and winters along the coast of east Britain (54–57°N) had a mean starting date of 21 July for primary moult (16 July for females and 24 July for males), a mean duration of 61 days, and completed on 20 September. Resident Icelandic (64–65°N) birds had a mean starting date of 22 July for primary moult (17 July for females and 25 July for males), a mean duration of 51 days, and completed on 11 September. Birds moulting in north Norway (70°N) arrived in north Norway in suspended primary moult or without having started moult, and completed it there. They had a mean completion date of 2 November for primary moult (31 October for females and 3 November for males). Starting date and duration could not be estimated because some suspended moult for an undetermined period, but it was thought that they started in late August. It is likely that most originated from Russia. The onset of moult appears to be set by the end of breeding and there is little overlap in these two events. The earlier start of moult by females in all three populations may be because they abandon the males when the chicks hatch, leaving the males to attend the chicks. Although the duration of primary moult followed the expected trend, being fastest in north Norway and slowest in Britain, the onset of moult was so late in north Norway that they had an unexpectedly late completion date, despite their rapid moult. The late completion of primary moult in north Norway suggests that wintering in the far north may not pose the energetic constraints on Purple Sandpipers that had previously been supposed.     

Is the heart of Fennoscandian rodent cycle still beating? A 14‐year study of small mammals and Tengmalm's owls in northern Norway

Analyses of spatial and temporal patterns of the small mammal cycle in Fennoscandia have led to two main conclusions: a south-north geographical gradient in the strength of density dependence and period length, and a change in temporal dynamics with less clear periodicity and lower amplitude of fluctuations in recent years. Fourteen years (1985–1998) of small mammals trapping and Tengmalm's owls monitoring data provided clear evidence for 3-yr cycles of two vole species in inner Troms, north Norway, at the same latitude and only 80 km from Kilpisjärvi, north Finland, where 4–5-yr cycles have been the norm until the end of 1980s. The response of Tengmalm's owls to variation in small rodents abundance was not delayed, as was observed in central Finland. Common shrews appeared to have more stable dynamics. The features of the cycle, and a reassessment of the previously described patterns, show that the dynamics may be different over short distances. Furthermore, snow cover and habitat fragmentation should explicitly be taken into account in any understanding of the Fennoscandian gradient, and surrogate variables such as latitude should be avoided. We stress the need for a more extensive coverage of spatial and temporal patterns in cyclicity with respect to assumed ecological causes.