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Predators of Mason Bees

 Frank wrote yesterday:

 Hi Margriet .. am forwarding an email (in mauve below) with images that I recently distributed to all the folks on my “Bee Team” concerning woodpecker damage on Galiano Island.  I think you will find them interesting.  
 
 Do you get many reports of this sort of thing, or do you have such problems with your own nesting boxes?
I hope the summer has gone well for you,
Cheers,   Frank
 
 
 
Subject: Woodpecker damage on Galiano Island
 
Hi Everyone ..  in response to my earlier email about the possibility of woodpecker damage to our nesting boxes, Paul brought two of his boxes to me from Galiano Island, where they had been thoroughly pillaged by woodpeckers.
 
One puzzling thing is that we have flickers and downies in our garden all year round, but never have any of them shown any interest in the nesting boxes.  And the site on Galiano where the damage was done has escaped predation for years. 
 
Anyway, that’s just one more element of mystery surrounding the life of our bees.
 
I’ve attached four images, one overall image of each of the two nesting boxes, and one detail of the worst damage on each one.  It looks as if the woodpecker(s) managed to clean out the front end of every gallery, even those where it(they) did not enlarge the opening i.e. there is not a single gallery left with chambers right up to the front entrance.  As far as I can tell, the first two or perhaps three chambers are gone, particularly in the enlarged openings.
 
Just how much damage has been done won’t be evident until we open them up in November.
 
It’s a jungle out there!
 
Cheers,
 
f.
 
By the way, if you are wondering what the markings are on the fronts of the nesting box trays, there is some evidence that decorating them in some way makes it a little easier for the females to find the galleries they are working on.  It’s not uncommon to see a female come back to the nesting box from a pollen-gathering or mud-gathering trip and enter a gallery, only to pop out immediately and go to a different one. Sometimes it takes more than two tries before she lands where she wants to be”
 
Hi Frank- these are good examples of wood pecker damage :)   and yes I receive these type  of reports nearly every year.
I think you are lucky a pileated woodpecker has not found these nests.  These giants can demolish whole mason bee homes.
 
From the look of the hole- depth, this woodpecker is likely to be the hairy or downy woodpecker.   You mentioned that they have not been predated on before.  this might be because of food availability.  Early in the spring, I have seen damage from bears, where they actually lick out the pollen lumps!  You would not think it would be worth it, but food must have been scarce at the time.
 
One easy way of protecting the nest from wood peckers is the hang them facing inwards- in July when flight has ceased.  Or you can protect them  with a predator guard.   Be aware that the predator guard has to be a good inch away from the face of the nesting tunnel.  Wire screen is NOT too successful.  I think  wire is usually too thin for the bee to see the wire when they come barreling in towards the nest.
 
If my nests are not protected in some way, woody woodpeckers are sure to find them here at home.
 
Oh by the way- I think the nests are still good to use- and the trimmings will assist bees to orient towards their nesting tunnels.  I would sand these rough chipped holes though.
 
 Margriet
 
reply from Frank:

Thanks for the suggestions of turning the boxes around or using predator guards.  Dick S. was very faithful about turning his boxes around each season, I know.  And I’ll pass along your comment about reusing the damaged trays.  You’re quite right that except for the one that was enlarged to the size of a loonie, they just look like someone had taken a countersink bit to them  I think that bird (or those birds) worked awfully hard for what they got!
 
I’ll let you know what we find when we open them up in November.
 
 

Hi Margriet,

I took the images of the Quicklock trays in the Highrise that have popped open.
As you can see there are a few empty holes now that previously had been full. It must be the chickadee as you suggested.

Do you think it is too risky for me to try to tape it tight again? I dont want to squish them but they are completely exposed now.

Your bee-loving friend, Eve

Hi Eve, I would not try and tape the nesting trays at this stage.  When they are done flying turn the trays so they are facing inwards- then the chickadees can’t get at the larvae.
Margriet

Quicklock Trays in a HIghrise showing tape has loosened
around nesting trays.

Brilliant!

That’s why you have a Phd  and I don’t. :-)

Hello Margriet.
This is my second year with a mason bee nest. When I cracked
open my corn plastic stack to clean my nest last year I was surprised to find two
of the tunnels occupied by spiders.
I had at least 25 cocoons hatch this spring. I went out o check on the house
on Tuesday and noticed webs around the house. On closer inspection, at least
three tunnels had fine webs over the openings.
I assume the spiders prey on the bees. Am I correct? And if so, how do I get
rid of them without disturbing the entire corn plastic bee stack?

Thanks,

Kevin K
That is a good question.  The only way I know is to catch and remove them from the site.  This would be quite difficult I think. 
 I have seen a jumping spider catch a mason bee!  So bees beware!

Check out your mason bee homes every now and then, and make sure you do not have a line of ants crawling towards the bees’ nests.  A good way of getting rid of them is to first remove most of the ants bysquashing them, and then have a water spary and then drip at the location where ants are crawling up the structure.  When the ground is wet, ants are discouraged from going in the direction of moist soil.

Harvesting cocoons from Corn Quicklock trays is fun.  You open two pieces of interlocking trays and you see what is inside.  Every row tells its own story and often it is a very different from the adjacent nesting tunnel.  It is great to see bees at work, but it is very exciting to see what they have produced and to see what other insects are using these nesting tunnels as their home.

This pink larvae has a brown head capsule.  It feeds on any detritus and pollen in the tunnel.  If left inside over the winter, it can chew through cocoons and destroy your bees.  After it has spun its cocoon, it emerges again during the early summer as a moth.  I remove these grubs from the nest as I harvest mason bee cocoons.

The warmth of the room where we harvested the mason bee cocoons warmed up the larvae and made it active.  It was travelling around the tray as I photographed it.  In the foreground are two mud walls dividing two cells each containing a male bee cocoon.  The female cocoon usually fills the space between the walls of the nesting tunnel.  Each cocoon is covered in frass and some mites.





Here is the larvae spinning its web  for its overwintering period.

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