The glyphs on the first page of the Voynich manuscript a subject of lively discussion these day on the VMs-list. So I thought it is time to summarize my view of them. I will speculate that the three glyphs mean (from top to bottom) - recipes, astrology, astrological medicine.
The glyph on the top is similar to the French capital letter R in its variation that includes an element shaped like number 2. This variation of letter R was used in medical manuscripts as abbreviation for the word 'recipe', based on A. Cappelli dictionary.
Based on that, my opinion about the first glyph is that it represents the herbal section of the VMs, which could be viewed by the author as "Recipes" section.
The second glyph was found by D'Imperio in Elegant Enigma to represent Regulus or Month. P. Han found the symbol on 13th century astrolabe ( see here ). Richard SantaColoma has a nice article with examples of this 'bird' glyph being used as paragraph marker in Post-Columbian Spanish manuscripts. (links to more examples can be found in the comment section).
The reason I go with D'Imperio's astronomy instead of paragraph markers is because the latter means the symbol should be marking most paragraphs, which is not the case with this VMs. In fact, the last paragraph on the first VMs page starts with a symbol that is suspected to be a paragraph marker all over the VMs.
So I believe the 'bird' glyph represents the calendar/astronomy/astrology section of the Voynich Manuscript, which comes after the main herbal section symbolized with the "recipe' glyph.
The third glyph differs from the second one by having additional doodle on top. The wavy thing, could represent a snake - symbol of medicine (the stuff of Asclepius). That way the whole symbol may represent astrological medicine as a 'title' for the anatomy/biology/bathing section of the Voynich manuscript, which follows the calendar/astronomy/astrology section.
So the glyphs, I am speculating here, highlight the manuscript content - the three major parts - Recipes, Astrology, Astrological Medicine. The last VMs part with possible recipes did not get a special glyph from the author - possibly just a paragraph marker :)