Protecting winter bluebirds

[millipede]

I hope this will make sense. Try to follow. HA

I don't personally have bluebird nest boxes so this discussion is just in general because of other discussions elsewhere.

I'm on two listservs, one for Oklahoma and one for Arkansas, that deal with birds. The other weekend we had snow and very cold weather... below zero weather which doesn't happen extremely often here. It was -11°F here one morning and other areas got even colder. Since last weekend(side note, it was 72° yesterday and the snow is gone now) there have been a lot of discussions about dead birds... mostly, but not only, bluebirds. People checking their boxes and finding piles of dead bluebirds. LOTS of such reports from both states and discussions that it's being reported in other states as well. I was thinking about it more this morning... I haven't SEEN that myself... I don't have nest boxes to check and I just haven't found dead birds anywhere. But, I have not reported ANY bluebirds since before that cold snap so, I think I'm seeing the results, just not finding bodies myself.
Someone commented this morning that a lot of the local CBC's this year had record bluebirds... and now we're not seeing any... so, that's a bit drastic.

I typed up a reply this morning with an idea... and, this is where I'd like input from all of you... either just your general impression or, even better if you have any first hand knowledge and advice...
Before humans started cutting down every "ugly"(I think they're cool) dead tree and before we introduced starlings, bluebirds had a lot more natural habitat and did not rely on us making nest boxes. I am thinking that many tree cavities would be warmer than your average nest box.
My ideas included:
1. Insulating current nest boxes. Think of a warm jacket. Something that velcroes or snaps onto an existing bluebird house giving it more insulation and more protection from the wind.
2. Taking down current nest boxes and put up winter boxes each winter... maybe slightly larger, THICKER walls, and perhaps straw or hay added as well. Maybe not as much "ventilation" as a typical house. 

The insulating idea could be something that someone could just put out IF they know a cold enough front is coming in.
The question here really is... would either of these ideas increase the likelihood of survival for these birds that huddle up out of the cold at those times?
or, are there other ideas?
Someone else mentioned brush piles... and I imagine that for some birds, brush piles is where they'd take shelter. But, I'm thinking that bluebirds are not one of them.

Anyway, anyone have any thoughts on this?
I am thinking that, unless someone has first hand knowledge, this might be something that would need to be tested in the field... which would be hard to do without having another severe cold snap.

[The Bird Nuts]

I wonder if it's not the cold that is directly killing them, but the lack of food/water.  I keep chickens and chicken experts always say they don't need insulated coops and they can survive extreme cold as long as there is enough ventilation to let the moisture escape to prevent health problems like frostbite and pneumonia.

[lonestranger]

I'm not convinced it's the cold killing them either. Up here in Ontario, we get Eastern Bluebirds year round and also get some pretty cold temps. If a couple of extremely cold nights was to cause their demise, I don't think we'd have them year round.

[Aaron]

Yeah I’m on boat with that the cold isn’t the direct cause.

Here in Alberta there’s been a single female mountain bluebird overwintering since December. She’s survived many days of temperatures well below -11f, with a week and a half of over night temperatures below -40c. And I don’t think there’s many nest boxes where she’s located as it’s inner city in a park by the river. But who knows what’s she’s been doing. 
And comparatively, I don’t think the general physiology of a bluebird differs all that much to more northern year round species of birds when it comes to dealing with cold. Pretty sure the only difference that makes a chickadee able to survive year round in Alaska is that they can access different food sources.

[millipede]

Hmmm....  interesting...  I'll mention this to the listserv and see what their thoughts are. I imagine some of the people had water available.
I can say that the local lake that I  normally see plenty of bluebirds at has water. Most of the lake froze but the creek feeding it had plenty of water, including good places for them to drink from.

A lot of the reports are just nest box after nest box with multiple dead birds.
I'm not sure what to think... but again, I'll mention it to the group and see if anyone reporting the issues has thoughts.
They're talking about multiple states with LOTS of reports. 😞

[MichaelLong]

maybe the bluebirds in the south aren't as tollerant of the cold

[Charlie Spencer]

23 hours ago, millipede said:

Before humans started cutting down every "ugly"(I think they're cool) dead tree and before we introduced starlings, bluebirds had a lot more natural habitat and did not rely on us making nest boxes.

As a side note, I question whether bluebirds rely on us for nesting places.  The only NA bird I'm aware of that is completely dependent on humans for housing is the Purple Martin.  Conservation agencies do provide housing for several endangered species, mostly those suffering from habitat loss as you noted.  But even those are not dependent on us.

Otherwise, I'm with everyone else regarding the cold not being a major factor.  I recall late last fall there was a large die-off of migrating birds in CA and AZ, and everyone initially blamed smoke from forest fires.  Then they found the real cause was a severe cold front had killed off most of the insects the migrants normally eat. 

[lonestranger]

While I'll admit that the harsh weather can be hard on birds and some will succumb to the cold, I don't think it would happen specifically to just one species. One thing that makes me wonder about this event, is the fact that so many birds were in the nest boxes. While I have only observed nest boxes from roadside viewing, I have never seen birds near them other than during breeding season. Is it typical for birds to seek shelter in nest boxes outside of nesting season? If so, do just bluebirds use bluebird boxes for shelter or might there be a battle with other birds over who gets shelter and who doesn't? We see birds frequenting our ornamental bird houses but only in the spring when they're looking for somewhere to nest. We've never seen birds coming and going from the bird houses any other time of year. Have I been missing out on activity in the off seasons?

[Kevin]

I don't think I have seen a bluebird since the cold front - normally I see them all of the time. I have not found any dead ones though. I have found 5 Pine Siskins, 3 Meadowlarks, and a Phoebe.

Edited February 26, 2021 by Kevin