In the mid-October, we found that a pair of Bali Starlings that are actively breeding around our Breeding and Release Center had 2 eggs in the nest box. This, of course, is good news. However, after we monitored it further, this pair of birds did not incubate the eggs. This indicates that these eggs will fail to hatch.
There are several reasons why Bali starlings do not always incubate their eggs. During hot weather, sometimes birds do not incubate their eggs, but at night or in low temperature conditions, birds will choose to incubate their eggs providing warm and stable conditions. There is also the possibility that the eggs are infertile so that the parent chooses not to incubate the eggs because they know the eggs won’t hatch. Some of the causes of infertile eggs are lack of nutrition, physical problems with the parent (hormonal or health problems), or environmental disturbances that cause stress and affect the fertilization process.
Sometimes, the Bali Starlings do not want to incubate their eggs because they want to reproduce again rather than wait for the eggs to hatch. This can happen if the bird has an excessive supply of food. Birds that refuse to incubate will sometimes damage the eggs themselves or throw away the eggs. Although October’s eggs failed to hatch, we will continue to monitor our released birds and hope for more chicks. Just as a follow up – we have two hatched in November. Hopefully these eggs will fledge safely! (Arie Maya Wijayanti)