How and What American goldfinches feed their chicks:
Like most finch species American goldfinches feed nearly exclusively on seeds and other plant materials and so do their chicks. Seeds are so important to the American goldfinch that they will actually hold off on breeding until mid to late summer in order to time the hatching of their chicks with the ripening of the seed crop. In particular, the goldfinch is waiting for the thistle seeds to ripen.
There are many varieties of thistle. Most are two to three feet tall and tend to grow in open fields, along road sides, in ditches and in farmers fields. They usually have prickles or thorns and they often grow in large groups. In general they are not well liked by many people but the American goldfinch loves them.
The American goldfinch feed their young a seed diet exclusively. Both male and female goldfinch will feed their babies. Now here is the interesting part. After feeding upon the ripened seeds the adults will return to the nest and regurgitate a mass of partially digested seeds along with a milky liquid. Stick with me for a moment while I explain why this is interesting.
A bird’s digestive system has two stomachs. The first is called the gizzard and is used to grind up the food in a dry environment. Since birds don’t have teeth they need this front-line stomach for grinding their food. The problem is, no real digesting occurs in the gizzard, just breaking up of the food. Digestion usually takes part in the second stomach where the stomach acids are located. So when a goldfinch regurgitates up the seeds it is assumed it comes from the first and not the second stomach. So where does this liquid mass come from? It is not known
What is known is that American goldfinch chicks grow extremely fast on the seed and liquid diet. What is more interesting is that the parents only feed their babies about once every 1 to 2 hours. Compare that to the insect feeding parents which are constantly stuffing their babies mouths with insects. Apparently the seeds and liquid diet is so nutritious the babies only need to be fed once an hour.
