Ceratina (calcarata) natural nesting habitat

[Donahue, Matthew]

Good morning Beeple, 

As part of my doctoral research I am planning to measure the abundance of nesting habitat for Ceratina calcarata. It's clear they nest in dead, broken pithy stems. But what constitutes a dead broken pithy stem in natural environments?

It seems like there's lots of work studying Ceratina in man-made, neatly cut Rubus, Solidago, etc. stems. But these obvious nesting spots are pretty scarce in totally natural areas, and instead, there are hundreds of Solidago, etc. bent at the ground (presumably by snow or wind) like in the below photo. Are twigs like this broken enough for Ceratina to enter? That would quickly change the suitable nesting habitat from 0 stems to 100s!

Thank you in advance for your insights! 

Matthew Donahue

University of Connecticut

[Jessie Novotny]

Hi Matthew,

I have been counting stems that are broken off and dead standing, both woody (Rubus, Rosa, Rhus, dead tree seedlings) and herbaceous (Solidago and other Asteraceae, Apocynum). But if they are bent in such a way that the stem broke and exposed the pith, that would work also. But if they are merely bent over and the stem fibers are intact and preventing the pith from being exposed, I haven’t been counting those. 

In my study systems, it is mostly deer browse that is creating the right kind of dead standing stems. So when I count potential nesting sites, I also count deer feces piles or whatever other evidence of deer abundance I can find. For example, in grasslands deer hoof prints create micro patches of bare soil that I have seen Lasioglossum and other halictids using. 

Good luck,

Jessie Novotny 

On May 18, 2026, at 11:03 AM, Donahue, Matthew <matthew...@uconn.edu> wrote:



Good morning Beeple, 

As part of my doctoral research I am planning to measure the abundance of nesting habitat for Ceratina calcarata. It's clear they nest in dead, broken pithy stems. But what constitutes a dead broken pithy stem in natural environments?

It seems like there's lots of work studying Ceratina in man-made, neatly cut Rubus, Solidago, etc. stems. But these obvious nesting spots are pretty scarce in totally natural areas, and instead, there are hundreds of Solidago, etc. bent at the ground (presumably by snow or wind) like in the below photo. Are twigs like this broken enough for Ceratina to enter? That would quickly change the suitable nesting habitat from 0 stems to 100s!

<Outlook-wjkdjltk.png>

Thank you in advance for your insights! 

Matthew Donahue

University of Connecticut

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[James Cane]

Kudos to you, Jessie, for taking on the question of Ceratina occupancy rates and even attributing the causes of the suitability broken stems. Ungulate browsing didn’t occur to me, but I will have to take note for the right kind of stems (here, moose and elk regularly trim red osier dogwoods every winter, but their stems aren’t pithy).

Jim

James H. Cane

Native bee and pollination ecologist

Emeritus USDA-ARS Bee Lab, Logan, Utah

owner -  WildBeecology

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[Spencer Hardy]

Another source of natural breakage that I've noticed is the Raspberry Cane Borer. It's a beetle that oviposits in the growing tips of rubus, leaving two rings of scares that cause the tips to wilt and then cleanly break. It can be a major raspberry pest and also quite abundant in wild settings. I often see evidence of Certina capitalizing on these breakages but have never taken the time to quantify it. I wouldn't be surprised if there were similar things happening in other plants (I know there is an Elderberry Cane Borer out there too). 

Photos: https://www.inaturalist.org/observations/125681417

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