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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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Pollinator Paradise      Pollination Ecology at UI    The Solitary Bee Web   
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New Mexico Native Bee Pollinator Project   About Dr. Strickler 
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