Average spectrum representation - SonicVisualiser
It would not be useful to average in time because vocalisations are represented directly by their spectrogram. (For example: http://www.u.arizona.edu/~ohalad/Phonetics/notes/Formants%20Spectrograms%20and%20Vowels.PDF or even http://www2.coloradocollege.edu/dept/ev/Research/Faculty/OVALItems/FordOsborneVocabulary/_SouthernVocabularyTable.html)

I would suggest that you export your spectrogram as an image and then isolate and layout the areas you are interested in, in some other software like GIMP. For more information, please see: http://www.sonicvisualiser.org/doc/reference/1.9/en/#imageexport and http://www.gimp.org/

Hope this helps.