A group of purple finches showed up at my feeder a few days ago and they reminded me of the first time I heard them sing.

I was out in the wilds of Spatsizi Park when suddenly I heard this joyful, bubbly, bird song. None of us knew what it was, and I thought for sure it must be some pretty pet bird noted for its song that had accidentally escaped its cage. Several years later as I started learning bird songs, I clued in that I had heard the happy song of our native purple finch.

Years later I was surprised to witness what looked to me like a female purple finch singing like an adult male. A birding friend told me that it was in fact a first-year male. They look very similar to the females with pale beige plumage streaked with brown, a prominent pale line above the eye and no sign of any rose-pink colour.

The juvenile males sing in the hope that a female will accept them even if they are not attired in their breeding finery. At this time of year (winter) the adult males are a pale rose-red colour that will gradually become more intense as the day length increases in preparation for breeding.

Roger Tory Peterson said that when the males are dressed in their finest, they resemble birds that have been dipped in raspberry juice.

I noticed that one of the birds looks quite yellow and I wondered if it could be a male that has not yet developed the rose/raspberry colour.

Research suggests it is not quite that simple. The birds get the red and yellow carotenoid pigments from their foods. Even if they get enough, they still may not develop coloured feathers because the pigments are also important for immune system function to fight disease.

The research also shows that the amount of streaking on a bird is controlled hormonally. Adult males with lots of testosterone will grow breast feathers with no streaking, whereas females and immature males will have broadly streaked breast feathers.

So, my streaked yellow finch may be either a male not producing enough testosterone, or a female producing too much.

Note: the raspberry colour is useful in distinguishing purple finches from their close relatives Cassin’s and house finches whose colouration tends to be more a true red or orangey-red.

editor@interior-news.com
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