  There is evidence for an excess in cosmic-ray electrons at about 500 GeV
energy, that may be related to dark-matter annihilation. I have calculated the
expected electron contributions from a pulsar and from Kaluza-Klein dark
matter, based on a realistic treatment of the electron propagation in the
Galaxy. Both pulsars and dark-matter clumps are quasi-pointlike and few, and
therefore their electron contributions at Earth generally have spectra that
deviate from the average spectrum one would calculate for a smooth source
distribution. I find that pulsars younger than about 10^5 years naturally cause
a narrow peak at a few hundred GeV in the locally observed electron spectrum,
similar to that observed. On the other hand, for a density n_c = 10 /kpc^3 of
dark-matter clumps the sharp cut-off in the contribution from Kaluza-Klein
particles is sometimes more pronounced, but often smoothed out and
indistinguishable from a pulsar source, and therefore the spectral shape of the
electron excess is insufficient to discriminate a dark-matter origin from more
conventional astrophysical explanations. The amplitude of variations in the
spectral feature caused by dark matter predominantly depends on the density of
dark-matter clumps, which is not well known.
