We studied a sample of 131 skulls of the stone marten Martes foina that were collected in Denmark between 1858 and 1999. Data were available for 37 years, but collection effort was not uniform throughout the study period and annual sample size varied between 1 and 27. We used principal component analysis (PCA) to combine the information of four skull measurements into a single variable (PC1). PC1 was then corrected for factors that significantly affected it (sex and longitude), and residual PC1 was used for further analysis in which we calculated trends in PC1 values during the study period. During the study period there was an increase in mean annual temperature in Denmark, but this increase was not continuous, as there was slight decrease in temperature between 1947 and 1965.We found that skull size (and by implication body size) of the stone marten in Denmark had two periods of decrease and these two periods coincide with the periods of increase in mean annual temperature. These results may indicate that body size of the stone marten is sensitive to the change in ambient temperature, either due to a change in food availability that was caused by the increase in temperature, or decreased its size in accordance with Bergmann's rule.

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SummaryIn a study of male song in the orange-tufted sunbird (Nectarinia osea) in an urban neighborhood in Ramat-Aviv, Israel, we discovered the occurrence of song variation on a microgeographic scale in the form of two distinct dialects with a sharp boundary between them. The main distinction between the two song dialects is the frequency of the trill, which comprises the terminal part of the song. A large difference of 2-3 kHz in the peak frequency of the trill was discovered between the two dialects, which could be easily distinguished by ear. Thirtyseven males were recorded singing the 'low' dialect and 21 birds sang the 'high' dialect. Four other birds sang both dialects or 'hybrid' songs. Along the boundary that separated the two dialect populations, neighboring birds sang different dialect songs, although they were only 20-30 meters apart. All four 'bilingual' birds occupied territories near the dialect boundary. The historical processes leading to the formation of this dialect system may result from the pattern of human settlement at the time of the establishment of this neighborhood in the early 1950's. The spatial distribution of the two sunbird dialect populations, and the apparent low dispersal rates of birds from their natal dialect area, suggest the existence of a mechanism, which currently maintains these dialects at the current boundaries.2) Corresponding author; e-mail address: leader@ccsg.tau.ac.il 4) We thank A. Elkayam for assistance in the eld and R. Zilberman for valuable information and help. We are grateful to L.F. Baptista, C.K. Catchpole and P.K. McGregor for providing helpful comments on earlier drafts of this manuscript.

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