Humidity Variance in the UK

Have just set 36 eggs, bit late and a bit of a risk but I wanted a chance to establish some new flocks before next Spring and with so much to do this has been the first chance to start a hatch. Anyway I have a Brinsea mini and a Octagon 20, the octagon 20 has a humidity readout and it has been interesting to see the variance from last time I hatched at a different time of year in a different location. I always run the machines dry for the first week to keep the air sac development ahead of the chick and the difference has surprised me, hatching in March in our old house we had 33% running the machine dry, here in August we are getting 41% dry which goes to show why you can get chicks drowned in egg if you don't have a humidity readout and follow the manufacturers instructions of adding water from day 1.

We had a discussion here a few weeks back about drowned in the egg Dinosaw. As I understand it the air sac needs to be large enough for the chick to get its head out from under a wing to pip. We ran dry here all through our last hatch up to lockdown. Although the machine used didn't have a humidity readout, at one stage, even running dry the air sac was too small. The humidity in the room was 80%- a result of a stone building with no damp proof course. The eggs were large fowl Wyandottes, the shells of which were noticeably less porous than the previous hatch of Leghorn bantams. The recent heat wave here has dried the walls out significantly and the room humidity is now 70%, so perhaps we would need to add water to the machine at some point. We work on the air sac development, so the humidity in the machine doesn't need to be monitored. Worth noting that the figure usually quoted for incubation of chicken eggs is 50% -this has to be an established 'average' because every breed or strain must have slightly different shell porosity as a result of genetics and diet. Many people report getting better hatches running the machine dry which means the humidity in it will be around the figures you quote Dinosaw, 30-40%. Even when we moved ours into the hatcher which has a humidity pump to take it to 75% it hardly used any water.

As a matter of interest what is the humidity in the room where you have the incubator?

Not sure Chris, don't have a humidity meter but we collect a fair bit of moisture in the dehumidifiers here. I generally find that once you fill the 20 with water and open the vent it pushes humidity up by 10 per cent so for me a week at 30-40 plus 10 days at 40-50 works well, I then assume the same conditions for the mini. The issue with these eggs will be I have bought them off ebay for the first time, case of beggars can't be choosers I'm afraid with what I am trying. To be fair the lady has very good feedback with a lot of people reporting good fertility and she was honest enough to tell me the fertility in her Orloffs had fallen off and give me double the eggs to compensate. We will see soon enough about fertility, how the postal system has done for hatchability is another thing altogether.

One thing I notice when we last hatched was that the sketch of air sac development shown in Katie Thears' book and reproduced in the Brinsea incubation guide is rather exaggerated. The sac shown at day 14 is sufficient for pipping. The sac shown at day 19 is irrelevant because with the increased humidity at lockdown day 18 there will be no further air sac development. The size shown at day one can vary tremendously depending on storage conditions. There is a relationship between temperature increase and humidity so it is possible to tell what the humidity is in the machine at 37.5C if you know what the ambient temperature and humidity is. I seem to remember the humidity drops by 20% for a temperature rise of 10C but would have to check that. Gail Damerows' book shows both a correct air sac sketch and gives a chart of humidity against temperature, which I must admit I don't understand at all!

I'm finding the Brinsea mini a nightmare this time round, took ages tinkering with the temperature screw prior to setting to achieve 37.5 and for the first 5 days it held its temperature, since then it has dropped off to about 37.2, all I can think is that the temperature screw is slightly loose and every time I take the lid off to turn the eggs it has moved slightly. I have done more tinkering up and down but it is such a small margin it is almost impossible to get it right, to make it worse I have 11 Thuringian bantam eggs in there which are showing 100% fertility. I am wondering whether it may be better to move them to the octagon along with the large fowl eggs which has a stable temperature but of course then I will suffer from different hatching times which is why I put the bantam eggs in the mini in the first place.

We've previously incubated bantams and large fowl together and they all hatched at the same time Dinosaw. Recently we hatched Leghorn bantams and Wyandotte Large Fowl separately, but they both started hatching at day 20 and were all out by day 21 (first day was zero).

Your slightly lower temperature may result in the hatch being a day late, but if it goes any lower I'd be tempted to move them. Sounds like you may need some spare parts.

Thanks Chris, have managed to fiddle the temperature back up to 37.6, not ideal to be having fluctuations but if it is falling over time then better that than it falling still lower, your probably right about fixing it I suppose moving 3 times probably hasn't done it any good. Humidity in the main incubator is up to 43% dry but it has felt very close here this week, Mrs Dinosaw has had a few headaches as a result, talking to a neighbour from along the road who has lived here a long time she described where we live as being a damp valley and indeed it does rise quite sharply both sides.

Did a day 10 candling today which has freed up enough room in the Octagon for the Thuringian Bantams and I have moved them after I came in today to find the temperature in the mini up to just touching 38C. Regardless of what happens from here on in I am very happy with the fertility of the eggs the lady sold me on ebay. The Thuringians were 11 out of 11 for !00% fertility!, Silver Sussex 5/6 for 83%, the Aracaunas are a devil to candle but I am thinking they are also 5/6 for 83% and the Orloffs were the least fertile at 5 from 12 but as I only paid for 6 eggs and she gave me 6 free due to the low fertility it works out at 83% again. Just a case of keeping fingers crossed now.

That's pretty good Dinosaw. Our fertility rate is running at 75% for both the Wyandottes (5 year old hens with a cockerel) and the Leghorn bantams (4 year old cock with 3 year old hen). The real test for the Wyandottes will be next year, but they are laying really well at the moment, as are the TNN's at 4 years old, and moulting isn't stopping them. Perhaps the increased sunlight is the reason?

Thats good going by your old girls, I wondered if you still had the TNN's, good to see them still with you.

They are very noisy now though Dinosaw. They view nest boxes as territory and will go in to shoo another out if they are laying in there. Just our luck as well- two nest boxes and all three want the same one.

Back to humidity variance. I don't think there is much in the UK. What I have noticed here is the tongue and groove weatherboard joints are pushed to their limits. I built the coops with the boarding deliberately wet, hammered them closed and fitted them to the frame. Then let them dry out and painted them. That stops them buckling as they would if assembled dry. Sheds here are a different construction entirely. 20+mm boarding is interlocked at the corners of the building. This allows the whole assembly to grow or shrink together, so in effect in dry summer the building is an inch or so shorter than it would be in a wet winter.

Chicks started hatching yesterday morning and by this morning most of what were going to hatch had, was very crowded in the incubator so I opened it up to remove the chicks that had dried off, one egg was still in the process of pipping and I managed to get the humidity up to 80% very quickly with hot wet kitchen roll and it hatched soon after. Three still in there now drying off, one is very very weak and I doubt will pull through. The bantams look nice healthy chicks, the large fowl less so, seem generally exhausted with a couple of cases of spraddle leg and curled toe that I am treating but we will see how they develop, I have to say that in an ideal world I wouldn't have had 26 eggs in one incubator at hatching but after the mini went haywire I didn't really have much choice, will have to buy another incubator going forward. I have put more pictures up on the photos page.

Lovely looking chicks Dinosaw. Opened the doors here at 2.00am to try to get some heat out of the place. It was still 24C but falling and the humidity was an amazing 94%. Noticed one of the coops has slipped a board- the tongue has dropped out of the groove and buckled the pair when the humidity rose.

Put them on Avipro Avian, rather than a spot of yoghurt- results at this end are amazing. I think they may be coming into lay several weeks early.

I'll give it a go Chris, Pets at Home are meant to stock it so will see if I can pick some up on Sunday. Am giving the spraddled chick some 'physio" sessions helping her to stand and walk with her bandaged legs and she is already showing huge improvement.