You’d never understand it by the unseasonably cold temperatures this week — I really hope the butterflies that recently arrived by the hundreds of thousands will fare all right — but it’s perfect breeding season for the feathered friends. If you couldn’t tell by the current weather, you'd certainly know it’s spring by the flashes of brilliant orange flitting through the woods, the flamboyant plumage used by male American goldfinches (Carduelis tristis) during reproduction season.

A couple of short weeks before, most of the goldfinches overwintering in our place — males and females alike — were wearing exactly the same drab, olive-brown plumage, with dark wings displaying two pale wingbars. Today, the males are decked out like royalty, and the females look like they certainly were dipped in a light yellow watercolour wash. Both sexes moulted their cold weather feathers, but just the feathers grew in with the gold. How did that happen?

Development of the finches’ silver feather colour begins with the meals they eat. Goldfinches are mainly vegetarian, choosing the seeds of thistles and sunflowers — seeds that eventually be laden with a number of orange-yellow pigments called carotenoids. They are the pigments that provide the characteristic color to peas, lovely potatoes, cantaloupes, apricots and a number of other foods.

Captive chickens fed diets lower in these pigments generally moult into duller colors, while those given diets richer included moult into happier whites and reds. This is the cause zoos offer flamingoes food rich in carotenoids: it assures they moult in to a great white colour, rather than washed-out pinkish white.

In the event of goldfinches, you'd feel both males and females eating from the same options would get the same amount of color in their diet, ergo growing feathers the same colour in the spring. Because that doesn’t occur, another thing must certanly be at work.

As it happens that feather colouration in goldfinches is under the get a handle on of hormones. Some authorities believe luteinizing hormone — exactly the same hormone that causes ovulation in women and stimulates the production of testosterone in men — can have a job.

Rebecca Kimball, an biologist at the University of Florida, claims that during the late winter/spring moult, both male and female goldfinches are believed to have high amounts of luteinizing hormone, which helps in the development of the bright orange breeding feathers. But the women also have a higher degree of estrogen during the same period, which could suppress the effects of the luteinizing hormone.

(Kimball says there might be a major advantage for the females not to be as vivid — it would, for instance, allow them to be much more hidden on the nest.)

That’s not absolutely Ebel Replica Watch all there's to the story, though. If hormones get a handle on the birds’ kcalorie burning of dietary pigments, what controls the hormones?

Among the many factors proven to control hormone levels in birds are heat, rainfall, day length, and the presence or absence of specific ingredients. Kimball says that for goldfinches, time length is probable responsible.

The biologist admits there’s a lack of certain studies done on goldfinch colouration.

“It will be good if we knew more in what was going on, however the data only isn’t there at this time,” she said.

Until those studies are done, the Midas touch that transforms male goldfinches from dull olive to brilliant silver will remain a bit of a mystery.

Star editor Margaret Replica IWC Watches Bream can be reached