Artificial Incubation Applied to Small Numbers of Altricial Bird Eggs : Part 4

Room temperature should not be too high or overheating and embryo mortality may occur. Some rooms are blessed with naturally ideal humidity conditions all year round, but with many it is necessary to add or remove moisture from the air. Humidifiers are especially important during dry periods such as in the winter and dehumidifiers during hot and humid summer weather. In areas where the climate is often hot and humid an incubator that has both minimum and maximum temperature and humidity controls may be the safest unit to use.

The importance of vitamin supplementation of seed diets was demonstrated by Roudybush (1984) who found a hatchability of 68% in cockatiels fed a vitamin supplemented diet with only 20% of fertile eggs hatching on an unsupplemented diet. The diet was a standard Cockatiel seed mix (6 parts millet, 2 parts canary seed, 1 part each sunflower, safflower, and hulled oats by weight) to which 10% hulled millet was added. The supplemented group received the vitamins coated on the hulled millet.

Thus it is important to have a sound feeding program in place which supplies all the required nutrients to a laying hen. Especially important for multiple clutching and maximum egg production is the level of calcium in the diet as egg shells are primarily calcium carbonate. The importance of calcium homeostasis is further demonstrated by its essential role in hatching muscle contraction during the hatching process (George, 1978). Most breeding pellets have adequate levels of these nutrients but if seed or bean-vege diets are being fed then a vitamin-mineral supplement formulated to meet the deficiencies of these diets must also be given daily. Mixing pellets with seeds will not provide a complete diet to birds who only select out and eat their favorite seeds and simply crush the pellets or throw them to the side.

Only, if after three days of piping the chick has not progressed in its rotation could it be carefully helped. Remove the shell above the air cell line with a pair of tweezers and lightly wet the membrane covering the chick with a fine mist of sterile warm distilled water, saline or lactated Ringers solution. If there are no blood veins within the membrane it can be cut and the head freed. Place the egg back into the hatcher, occasionally wet the membranes covering the chick and hope the chick will free itself. Death usually occurs when assisting chicks which have not yet resorbed the blood from the vessels in the egg membranes. It appears that the chorioallantoic circulation remains functional until shortly before hatching and remains even when yolk resorbtion is complete and the embryos are vocalizing (Bucher and Barnhart, 1984). Thus the correct time to assist an egg is hard to judge and its better to wait rather than have a chick bleed to death in your hands.

Some of the birds that HARI has tried to help out had unabsorbed yolk sacs. These eggs were sometimes first incubated by the parent birds who may not have kept the eggs warm enough and thus slowed their development or they were amazon and macaw eggs which may have not lost enough water during incubation. If you see an unabsorbed yolk sac immediately stop breaking away the shell and place the egg back into the hatcher. Hopefully the chick will free its self once the yolk sac has been absorbed. To speed up drying and prevent infection, swab some diluted tamed iodine onto a raw umbilicus or unretracted yolk sac.

Trying to assist a hatching egg can be very frustrating with most cases usually dying. All efforts should be made to have the correct incubation conditions so that eggs hatch naturally.

Artificial incubation can be frustrating; it can be an art as well as a science. However loses as well as successes provide experience and information on each particular set-up and corrective measures can then be taken. Unfortunately some breeders operate on a trial and error system, waiting to see if their eggs will hatch under the conditions they have set up and only changing the conditions based on the way the eggs have died. Measuring the rate of egg weight loss and comparing it to accepted ranges can indicate if humidity changes are required before the egg is lost.

The optimum incubation temperatures for altricial bird eggs in forced air incubators appears to be between 36.9-37.5°C (98.5-99.5°F). The mean overall fractional weight loss (the percentage of the initial egg weight lost) (fn) for most altricial species is in the range 12-16% with the freshly laid to pip loss in the range 10-14%. The optimum fn for individual species may fall at either end of these ranges. It appears the level of incubator relative humidity needed to achieve maximum hatchability in some species is higher than those previously documented. More controlled scientific studies are needed to compare incubator relative humidity, egg weight loss and hatchability.

Once eggs have piped they should be moved to a hatcher which has a much higher humidity and slightly lower temperature than the incubator. Hatching takes about two days and then the laborious task of feeding a blind, helpless altricial chick can begin.