# fetch file
download.file("http://rug.mnhn.fr/seewave/WAV/alauda2.wav", destfile="alauda2.wav")
# load file
s <- readWave("alauda2.wav")
# generate a tall png file
png("skylark_vert.png", width=8000, height=32000, point=120)
par(mfrow=c(10,1), oma=c(5, 5, 1, 1), mar=c(4.5, 0, 0, 0), lwd=6)
t <- seq(0, length(s@left)/s@samp.rate, length.out=11)
for(i in 1:(length(t)-1))
  {
    spectro(s, ovlp=75, scale=F, tlim=c(t[i], t[i+1]), tlab="")
  }
mtext("Time (s)", side=1, out=TRUE)
mtext("Frequency (kHz)", side=2, las=0, line=3, out=TRUE)
dev.off()