Weigh Your Eggs

A normal egg is expected to lose about 20% (plus or minus say about 2%) of its weight over the course of incubation. A macaw egg weighing 20 grams will weigh about16 grams at hatching.

The key here is the word normal. In humid environments there might not be enough weight loss, then the air sac isn't big enough and the chick "drown" in its own fluids on pipping. Here in Colorado we have very dry air. The problem here is the eggs dry out too fast. In my aviary, some of the birds catch on and get their feathers wet in the water bowl and then sit on the eggs to increase the humidity in the nestbox.  But most of the time hatching is affected by eggs that have lost too much weight. By incubating   as soon as possible - the day the egg is laid if not sooner- :-) , the weight loss can be monitored and controlled.

Assuming that the weight loss should be in equal amounts every day a chart that projects what the egg should weigh can be made. I weigh once a week. So when the egg is 7 days old it should have lost 4% of it's weight. Why 4%? Figure 28 days to hatch and assume a linear weight loss. Divide 28 days by 4 gives you 1/4 of total weight loss every 7 days. Projected total weight loss is 20%. 1/4 of 20 is 5, hence 5%. So at 7 days multiply original weight X .95 = projected weight loss at 14 days multiply original weight X .90 = projected weight loss at 21 days multiply original weight X ..85 = projected weight loss

If the egg has lost too much weight , then increase the humidity in the incubator. If the egg has lost too little, then reduce the humidity. About 83 to 85 degrees on the wet bulb or 45-50%  humidity is about right when an egg is on target. The eggs should tell you how much humidity you need to have.

You'll need a scale to weigh these eggs. A triple beam balance scale weighs down to 1/10 of a gram and that is close enough. I have a 4 beam scale that weighs to 1/100 of a gram.

So what happens when an egg has been in the nest for a week before you discover it? How do you know how much it weighed when laid? Well you make your best guess based on past performance. Good records - a daily diary of life in the aviary - will give you a hint. If your tendency is to have eggs that dry out too fast, then make a guess. I know in my aviary that eggs in the nest dry out almost exactly twice as fast as they should. In other words, after a week, the egg in the nest has lost 8% of its weight when it should have lost only 4%.

Now if you had more than one incubator you could really manage your eggs well. Set one incubator up at the ideal 84 degrees on the wet bulb and 99.3 degrees dry bulb gives you a relative humidity of 53.4% Then set up another incubator with 88 degrees on the wet bulb and 99.3 degrees dry bulb gives you a relative humidity of 64.1%. Place your eggs that are too dry in this incubator until weight loss is close to target weight. When target weight is reached, move the egg to the "ideal" incubator. The third incubator could be used just for hatching babies, or for a backup, or just cleaned and ready for the next clutch to be laid.

Cleanliness is crucial -- no.... cleanliness is the key to successful hatches. 

I don't run an incubator for more than 35 days or so before a complete breakdown and cleaning of all parts. If you don't clean your incubator you will lose eggs! 

I recently talked with a lady who had run her incubator continuously for 90 days without cleaning it. After great results for 2 months she started losing eggs --  hmmm. is that operator error or incubator error? It's your job to manage the incubation process. 

So where do you put your eggs when you're cleaning the incubator? I put mine in another clean incubator. Having an incubator just for hatching is a pretty good idea. Having a separate place for hatching  eggs just might keep a bad egg from contaminating the others. And the common thinking is babies that have pipped (broken through the air sac in the egg and made the first hole in the shell) should be held at a slightly lower temperature - about 98 degrees and at a  elevated humidity - nearly saturated air at 90-100% relative humidity.

Our Small Cooler Brooder makes an excellent hatcher, - easy to achieve high humidity and very accurate temperature control. Also a great place to temporarily store your incubating eggs while you clean the incubator.