Feeding Mason Bees
If early spring nectar sources seem limited,
feeding mason bees may be an option worth exploring to raise their energy
and activity levels for pollen foraging. Probably, a feeding station near
the nests would substantially increase the orchard nesting rate of emerging
bees in addition to their overall number of cells provisioned. This seemed
to be the case in my experiment with feeding Osmia lignaria one season.
I devised a fairly simple but effective enough
small-scale feeder for my Osmia bees using the principle of the chick-waterers
that we commonly see. My simple feeder, suitable for a few hundred nesting
bees, but which could easily be expanded upon in principle or design for
large populations, amounted to an upside down mason or mayonnaise jar (pint
or quart), set on a plate where the nectar pooled due to small slots cut in
the plastic screw-on lid. The sugar or honey-water solution reached a level
on the plate which stayed more or less stationary due to the chicken waterer
principle where more nectar leaks out once the level drops enough to allow
air into the slots cut in the lid. A doughnut shaped screen (preferably
plastic or stainless steel) with about 1/8 inch mesh, covered the plate and
nectar, and the hole cut in its center fit snugly around the upside down
lid. This snug fit was essential around the edges of the plate also ( use
tape, glue, fasteners, anything that works) to keep bees from finding their
way into and drowning in the solution.
In my feeder, some control over the nectar pool
level could be obtained because I drilled three holes in the plastic jar-lid
and added short legs for it to stand on in the form of stubby stainless
steel bolts with nuts on either side of the plastic to allow adjustment of
the bolt lengths protruding (about 1/4 inch protrusion). Thus the upside
down jar could be raised slightly off the plate to deepen the pool of
sugar-water solution on the plate. Some fine tuning enabled one to find a
feed level which rarely overflowed the screen and stayed ideally around 1/8
inch under it, in easy reach of the feeding Osmia bees.
Initially, Osmia or other solitary bees probably
won't feed very readily at such a feeder without some enticement and
conditioning. I accomplished this by positioning the feeder directly in
front of the nests (within a few yards and in an ant-proof location). The
bees were conditioned to feed at the feeder by scattering some fresh flower
petals upon the screen each morning. These were sprayed with some of the
sugar-nectar solution, and bees landing to investigate them would usually
discover the nectar droplets upon them after some probing. Further feeding
and probing through the screen resulted in regular visitation and feeding
from the underlying nectar pool. The visiting bees themselves seemed to
attract others in growing numbers and eventually this small feeder was used
by large numbers of my mason bees, usually as they were leaving the blocks
to forage. I am fairly sure that it substantially increased their foraging
range and energy levels, and resulted in greater than normal nesting rates
that season.
There were some technical drawbacks to my rather
simple and crude feeder design. One was that it was a bit labor intensive
conditioning the bees, and also fresh flower petals needed to be added every
day or so to keep up a high level of interest and visitation from the bees.
Ideally petals from a preferred forage flower would work best, but I often
used those of yellow composites, which still seemed to be attractive enough
once they were found to have a sugary reward. If the bees were cueing in
upon ultraviolet light, it would seem logical to find a synthetic
attractant, such as ultraviolet emitting plastic petals or flower shapes to
solve this problem.
The sugar solution would tend to crystallize
more and more over time, and washing the plate and jar with hot water
periodically was a good practice. Also the jar would heat up in sunlight
and then increased air pressure would force more sugar solution out of it
and sometimes flood the screen. A foam insulating cover over the jar helped
somewhat, but a better solution would be to use a feeder with a float-switch
activated reservoir of feed separate from the screen-covered feeding tray,
but draining into it through a tube. A float switch itself would not be
necessary if one simply continued to use the chick-waterer effect from an
inverted feed container jar with a tube coming out of it, and let the tube
outlet determine the sugar-water level, but the float-switch method would
allow for a more remote placement of the jar or nectar source. In such
setups, the feeding tray could then be virtually any shape or size for very
large numbers of pollination bees. Another option, having the
landing-screen floating upon the sugar solution directly, might prove
problematic due to sugar crystallization buildup affecting its performance.
I dissolved sugar in hot water, trying various
ratios in the feed solution. Typically these were up to 50/50 by volume for
the sugar and water, but often more in the range of 1 part sugar to 2 parts
water. Perhaps honey should be used, but I lacked information on just what
to feed mason bees, and could find no references for it. It is hoped
that an ideal feed solution can be determined by others with more knowledge
or experimentation in this area.
No doubt, fellow enthusiasts of alternative
pollinators and native bees can elaborate upon, improve, or come up with
their own versions of native bee feeders with a little tinkering and
experimentation.
Steve Dupey
Twisp WA
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