Bee hotels / houses

I am thinking about putting up a bee “hotel” in my yard. (Such as https://smile.amazon.com/s?k=mason+bee+houses+for+the+garden&crid=24ZY8HJDDYWC9&sprefix=Mason+bee%2Caps%2C227&ref=nb_sb_ss_ts-doa-p_6_9) . those are cute, but I’ve seen much larger ones.

But, I wondered first if bee-knowledgeable people think they are effective or useful? ?They seem like a good idea, and I’ve see cute ones from time-to-time. But the ones I’ve seen were unoccupied.

So, I wondered if having the tubes so close together was not so good or attractive for the mason bees?

Do the bee houses perhaps promote disease or possibly not serve territorial needs?

What can you tell me about Mason Bee houses?

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I have a bee hotel in my yard that looks fairly similar to that one. It only has a few “residents” this year (maybe 10), and a couple spider nests, but I consider that successful enough. Whether your bee hotel is “successful” or not depends a lot on what kind of bees you have in your area and what their nesting preferences are. Beware that some people are opposed to bee hotels, and consider them harmful to bees due to spreading diseases and parasites. As long as you clean your bee hotel every spring, though, I really don’t think this is a problem (although I won’t be surprised if someone here strongly disagrees). Personally, I think they are great, as they provide nice nesting sites for bees (and spiders) and also facilitate humans learning more about solitary bees (which is just as important for bee conservation I think).

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Note that here I am talking about solitary bees only not going any further to genus level.
don’t worry bee hotels are very helpful, as it provides good shelter for solitary bees to live, and they will be easily attracted by holes in your bee hotels, they don’t really care whether they attractive or not, as per your question about the disease, yeah there is the possibility of disease spread in solitary bees, but still, it is a good measure for conserving solitary bees. To prevent disease I always use a dried hollow stem of any small plant as tubes when one tube of my bee’s hotels gets used by a bee I replace it with another tube of the same width. You can make your own DIY project of bee hotel if you want
And it is a good initiative taken by you, I love that idea because everyone talks about honey bees, no one talked about solitary bees which are unsung hero, You know solitary bees are literally majority of bees as we compare to honey bees, and there pollination success rate is more than 90% as we compare to honey bee which is only 5%, No hatred against honey bees or honey just we should protect solitary bees and native bees :)

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I don’t have a lot of experience with them personally, but all of the objections that I run into (not cleaning them, non-native species using them, seem to be the two big ones), are issues that bird houses face, and I don’t think that anyone will deny that bluebirds, swallows and others have greatly benefited from properly maintained nest boxes. If you live in a more urban area, then you might have more non-native Osmia than native but that’s not the fault of the house, it’s the surrounding environment. I live in a sub-urban area and have to deal with House Sparrows in my bluebird boxes, but I’ve had Bluebirds, chickadees, and wrens use them every year.

I would be curious to see just how many native species make use of those (I’ve heard of a couple), and if native plantings effect that.

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I’ve saved this blog post link for just this occasion:

https://colinpurrington.com/2019/05/horrors-of-mass-produced-bee-houses/

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Yeah you raised an interesting question I almost forgot about that, now I will have dreams about this question only. But bee hotels are our one of the only hope, and I still don’t know native bee species around my house when I search the bee species the common thing that comes on Wikipedia is that it is widespread throughout asia

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Very true and definitely worth a read for anyone who is thinking about putting up a house. However, to my point about birdhouses, there are terrible bird house out there that really aren’t suitable as a nesting site, but there are well designed/built boxes that are quite beneficial, but whether for birds or bees both should be maintained by the people who put them up.

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One thing to point out, the only bees that use these are cavity nesting bees which I believe are all members of just one Bee family Megachilidae. Andrenidae, Colletidae, Apidae, Halictidae ect are all also natives, many solitary but they all have other nesting requirements.

Making sure that you have things like bare soil, sandy areas, compost, are all good ways to cater to some of the other families, and those other families have fewer non-natives to worry about. Another one is if you happen to back up to a park or conserrvation area, contact them and ask if they have ever recorded floral specialists on that property and plant for that specialist (but of course make sure you’ve got a good spread of native plants blooming for as much of the year as possible).

To add one more thing, the people that I know who maintain bluebird boxes know a lot about bluebirds, swallows, wrens, and sparrows. I would strongly recommend that if you are trying for native Osmia or Megachile, learn as much about them as you can, so you know when to put the house up, when to take it down, if your house needsd modifications (I know a woman who really likes a particular bluebird house that she buys in our area but she feels that it doesn’t have enough overhang so she adds a piece.

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Bee hotels can be effective and useful (or have pitfalls), if the right design is used correctly. Designs should ideally address considerations like protecting against rain with a cover, and birds and squirrels with a screen. There are also tips for management, cleaning, and when to remove cocoons. Bees can be attracted by adding flowers/habitat features nearby, or using a bee spray. The Crown Bees brand has gotten good reviews. They also have walkthrough educational info. worth reading on it’s own. They make mason and leafcutter nests (different tube diameters attract different taxa), and sell bees for them. Having tubes close together isn’t necessarily an issue, and they’re unlikely to spread disease if cleaned/maintained enough. The main bees are Megachile and Osmia (Megachilidae). Hylaeus (Colletidae) can nest in some tube diameters. Ceratina (Apidae) nest in pithy plant stems (for habitats or hotel nesting materials you can add yourself). Finally, cavity-nesting wasps, ants, spiders, etc. may also enter nests, which may be pests, or could be studied/raised themselves.

Although, it’s never guaranteed that bees will visit a hotel. The one I tried so far had that difficulty (only ants and spiders visited it), although the issue probably was a lack of flowers nearby it for most of the summer.

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I’ve had some mixed success with adding a bee house (I have one of the Crown Bees ones). I did some modifications to keep the rain out and protect it against woodpeckers. There are plenty of flowers (fruit trees, shrubs, native perennials) throughout the year, and I have clay soil and a water source (creek) nearby and mason and leafcutter bees around, and also various species of mason wasps that visit my flowers. So I was expecting the bee house to see a lot more activity, but it’s been mostly just for decorations.

Some bees and wasps have nested in the house, but their number around the yard seems to be far greater than the number of tubes occupied. I have noticed some spiders and a lot of ants going in and out so that may be an issue if the ants are cleaning out the nesting tubes before the bees can close them. Or the bees may simply prefer other, more natural options. I’ve had the best success with natural reeds in the house over the paper/cardboard tubes, and I’ve had more wasps than bees when I looked at them.

Whenever I cut down perennials with hollow stems, I stack them into a brush pile near my compost. So I always have plenty of stalks around the yard to host solitary bees and wasps and given the choice they may prefer that messy perennial pile over the bee house. Bird activity over the winter also suggests that there are some nice snacks to find in there.

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I have had one of the “Bambeco Mason Bee Barn” (scroll down the page cited) for 2 years. It hangs under the eave of a breezeway in front of an herb & flower garden.
The side sections are varying size reeds, and the center section is holes drilled in a block of wood.
They much prefer the reeds over the holes drilled in wood.
I have Sambus in my backyard, and when I need to prune them, I drill a small hole near one end of each section when they are dry and Mason bees love them.

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In case useful, here are my tips on how to make and maintain a hotel. I’ve also made a post about where to buy good hotels.

For those of you who like to join projects on iNaturalist, please consider contributing to Bee & Wasp Hotels.

I’m also a huge fan of setting up bee and wasp hotels in places that might entertain passersby, with the goal of getting more people to appreciate tunnel-nesting insects. I put one in my front yard, and lots of people stop and try to figure out what what on earth it is. My mail delivery person checks it whenever he goes by and he said he’s going to build one, too.

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I’ve used both pre-made and homemade bee hotels (the tubes, and holes drilled in logs). Generally, bee hotels made from tubes tend to attract a lot of Osmia cornifrons, a non-native megachilid, at least in this area (northeastern US), and in my case they were the only occupant. The one with log holes attracted primarily potter wasps, which is fine by me. But proper cleaning is crucial and the timing can be tricky - when the Osmia emerged from mine, they immediately tried to re-nest in the same box. There are also concerns that having so many nesting sites unnaturally close together can increase risk of parasitism or disease as well.
However, when possible, it’s likely much better to provide natural nesting habitat than artificial bee hotels. This can be as simple as leaving patches of bare dirt, or loose small stones, especially if you have sandy soil in your yard, as most bees are ground-nesting. For cavity-nesters, many native garden plants have sturdy stems that offer natural nesting sites - I like using dry dill and bee balm stems, native grasses and Rubus canes also work. You can either cut these yourself once the plant has dried and stake them around the yard, or just cut the dead stems back in spring instead of fall/winter so the fresh nest sites are available for bees to chew into (and the seed heads remain for birds through the winter). In my yard, the Ceratina nest in Hydrangea stems as well. You can also get Hoplitis, Hylaeus, and a variety of solitary wasps (I had a very adorable crabronid take up residence in a dill stem I left standing). Snags and logs are also great for many cavity nesting bees, like Augochlora and Xylocopa. Many times, the best thing we can do is just manage the resources we already have, instead of buying new things!
But bee hotels can be beneficial for educational purposes, and to get the public, and kids, interested in pollinators. It can also be helpful for monitoring/photography purposes.

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Most of this makes sense, but I have a question about one particular thing. It mentions opening the tubes to examine the pupae and check for the presence of parasites. My question is: don’t the parasites need conservation, too? If they only live on native bees, and native bees are threatened, those parasites are threatened as well. Like how species of parasites that live only on certain species of endangered bird are also endangered. Now, I know they’re parasites and people don’t tend to like them, but they shouldn’t matter less just because we don’t like them. And parasites serve important roles in the ecosystem, too.
Replacing the tubes makes sense; old natural tubes would break down in nature. But there’s nobody in nature going around opening bee nesting spots to check for parasites.

To be clear, I understand throwing away/cleaning old tubes so unnatural amounts of parasites don’t build up. But the amount of parasites from one year seems like a natural amount, and that link mentions parasitic wasps. If I remember right, most parasitic wasps target only one species. So if they have a reduced amount of breeding opportunities due to people removing them, that seems like a bad thing for the wasp species.

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I agree that parasitic hymenopterans should be given their due consideration when it comes to conservation (plus they’re super cool!). Many parasitic species of bee and wasp are host-specific, though there’s plenty that aren’t, and indeed it’s thought that some are declining or potentially endangered due to a loss of their hosts. However, this is unlikely to apply to a bee hotel situation, as the bees nesting in these artificial nests are probably common species already present in an anthropogenic environment. Rare or imperiled parasites tend to have rare or imperiled hosts, at least when it comes to parasitic bees.
It all depends on what the ‘goal’ of the bee hotel is - if one is looking to increase the population of pollinating native bees, having many of those nests produce kleptoparasites instead is an undesired outcome, as they are not generally very efficient pollinators. In that way, bee hotels can be an ecological trap, encouraging bees to nest but leaving them vulnerable to nest mortality from various sources by being concentrated. But if the goal is to observe nature, then those sorts of interactions or unexpected outcomes are fascinating!
There are many kinds of parasites and diseases that can afflict the bees using a bee hotel though, not just other insects, and these mites, bacteria, and viruses can reside in the nest and build up over time so the next year’s brood face much higher mortality if the hotel isn’t bleached or replaced. Unfortunately there still have not been very many studies to quantify the risks or benefits of bee hotels, as there’s so many factors that can influence bee nesting success in these situations.
Here is one:
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0122126

That being said, there’s so many designs for bee hotels, we don’t know how they differ in their success rates and occupants. Ones that are more ‘natural’ (like incorporating natural materials, are set up in a more three dimensional or ‘messy’ design) may attract more native bees or reduce parasite risk. But these generally are hand-made. It bridges the gap between an artificial nest environment and providing natural nesting sites.
Here’s one that I like from my alma mater:


(photo from Sandra Rehan’s Bee Lab at UNH, where I did my undergrad, they’re now up at York U)

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Re: ecological/conservation costs and benefits, it seems complex and partially unknown. I’d draw an analogy to urban gardens, parks, and green roof habitats. Each also pose some limitations for habitat quality and attracting native (vs. exotic) bees and plants. Exotic plants are overly used, which worsens the issue of exotic bees already being overrepresented in urban habitats. But, with sufficient acknowledgement of limitations, and conservationist design and maintenance (aided by research), those can have benefits for bees, including natives to some extent.

The question for hotels like for green roofs shouldn’t be what would the ecological effect be if they were everywhere. There could be downsides. Yet, qualified strategic uses have been demonstrated to be helpful for GRs (vs. articles saying GRs are universally bad).

If people use hotels in a conscious way I doubt there’s any appreciable population-level risk of (increased) exotics, parasites, or disease (some megachilids are also native, and as far as I know exotic megachilids aren’t overly harmful, vs. the impact of A. mellifera for example). One advantage is pests etc can simply be removed as they arise, or hotels can stop being used if poor success persists. I think qualified conservationist use of hotels is one part of helping research how effective these designs can be, and what could further improve/refine them to potentially even help conservation more clearly eventually (article here, also cited above). That said in case clarity is needed, I also still overall support emphasizing native plants and native bee habitat.

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Yeah… I was driving through the Florida Keys once, and came upon what was claimed to be “the southern most purple martin house.” Well, you could have fooled me; I would have sworn it was the southern most house sparrow house, to judge by the occupants.

It should be said, solitary bees are not the only kind that can use provided “houses.” I have seen bumble bee houses, too, although I was not able to get bumble bees to use them.

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Most bee hotels for sale are a waste of money, mostly because bees prefer smaller holes than the cheap bamboo ones that everyone seems to sell.

Some of the best DIY ones I’ve seen are just holes drilled into a log or block of wood.

The narrative that bee hotels are “death traps” is scaremongering that seems primarily designed to drive clicks.

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Cleaning bee hotel has its serious disdvantages :( Cleaning is often a form of maintaining breeding colonies of solitary bees which are used for commercial pollination. These bees are maintained in very high numbers and densities. In such circumtances diseases can spread more, and besides, owners of these bees want many bees of this one species because they use them commercially. On the other hand, if you have “bee hotel” (or maybe rather “insect hotel”) because you want “help bees” or simply look at wild bees nesting in your garden, cleaning nests can harm bees other than commonly bred species. Some bees overwinter as larvae and they can be mistaken for parasites, or get destroyed during opening of nest. And there are also solitary wasps which can live in your bee hotel, and… there are even parasites which are ineresting and why should they be killed? For example, there are even bees which parasitize other bees (eg Celioxys - I’m writng from the European perspective so example from my area). If you are concerned for too many parasites you can put smaller bee hotel, or clean it every few years, or change only part of nesting material.

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It’s true that bees that can nest in bee hotel are minority of species (so bee hotel cannot be only activity if we want to protect bees seriously, we must remember about bees nesting in other places like soil, and o course about food for them all - flowers). But there can be more than just Megachilidae, and it depends on how you build your hotel - the more diverse nesting material, the better. For example, some Hylaeus (family Colletidae) nest in empty twigs, and as far as I know one species of Colletes can soometimes come to bee hotel. Anthophora plumipes (Apidae) can nest in mud blocks which can be added to bee hotel. Ceratina (Apidae) nests in twigs with soft core.

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