The total volume of pollen available to a colony may well be the most
limiting factor in the development and expansion of the hive
population. Even if a colony has access to a mixture of pollens or a
single high quality pollen, if there is not sufficient quantity then
this will have a major impact on the available food for developing
larvae and young adult bees. In this context, it is arguable that
beekeepers should be first concerned about the volume of pollen the
colony is collecting and storing before turning their attention to the
quality, although decision making processes should consider pollen
sources that provide both quantity and quality.

As the strength of a colony and the demands of a colony vary
significantly according to the time of year and even between colonies
on the one location, it is difficult to conclusively state what
species consistently produce significant quantities of pollen. The
climatic conditions prevailing at the time of collection will also
impact on the amount of pollen produced and released by the target
plants. Even so, in this trial, significant plant species that
demonstrated their importance as a source of pollen due to volumes
collected by bees were Paterson's curse, Canola, Turnip weed, Apple
box, Spotted gum and Sunflower.

From these six species, Sunflower pollen is of significant concern as
its crude protein levels are very poor, thus bees may breed well on
the volume of pollen supplied but the adult bees are likely to be
short lived. If a colony of bees working a Sunflower crop, from which
bees obtain most of their pollen requirements, is moved onto a heavy
honey flow the colony would be expected to collapse or seriously
diminish in population due to the low body protein levels of the adult
bees.

We can divide the plant species into three general categories: Pollens
that will not sustain the growth and development of a colony; pollens
that will sustain a colony but only under light honey flow conditions;
and average colony replacements and pollens that should be sought
after if colonies are to be working a heavy honey flow following the
breeding of a few generations of brood.

Species with mean crude protein levels below 20% include: Black she
oak, Black thistle, Blueberry, Buckwheat, Capeweed, Citrus, Eggs and
bacon, Flat weed, Lavender, Maize, Nodding thistle, Saffron thistle,
Silky hakea, Sunflower and Willow. If these pollens are the dominant
or only species being collected, then it can be assumed that the
colonies will decline in populations, particularly if they are made to
work a medium to heavy honey flow following the feeding of this pollen
to developing larvae and young adult bees.

-- 
Nutritional Value of Bee Collected Pollens
Rural Industries Research and Development Corporation
www.rirdc.gov.au/reports/HBE/01-047.pdf

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