Thursday, November 18, 2010

Black fantails and and white blackbirds

I have been asked on several occasions about black fantails in Greytown. Indeed one of my reporters was a bit afraid he might have been imbibing too much and was very much reassured when I said that yes, we do have some black fantails in Greytown.

I have seen black fantails down Hawk Street, Wood Street, Mole Street and even near the park on Kuratawhiti Street, usually quite happily paired with a pied fantail.

There are three plumage phases or morphs in fantails: the pied phase has a grey head, white eyebrow, brown back and yellow under parts. The chest is banded and the tail is mainly white. The juvenile phase is similar but has a browner body and indistinct body markings. The black phase is overall sooty black with a white spot behind the eye. The black fantail is not regarded as a sub species but is a genetic colour variation within the species, like black sheep. They breed freely with pied fantails.

Black phase fantails are found mainly in the South Island and are quite rare in the North Island. In all the twenty-five or so years I lived in the Bay of Plenty I never saw one, so we are quite privileged in Greytown. Why they are more numerous in the South Island is a matter for speculation. The darker colour may be selected for its survival value in the colder climate.

The other birds that get some comment are the blackbirds down Wood street which often have some white patches on them. It is not altogether uncommon to see perfectly white blackbirds. These are usually leucistic birds, not albinos. I have also seen a perfectly white Tui.

Leucism is caused by a mutation that prevents melanin from being properly expressed in feathers. The plumage color changes may be white patches, paler overall plumage that looks faint, diluted or bleached, and overall white plumage.
There are distinct differences between albino and leucistic birds. Leucism affects only the bird’s feathers, and typically only those with melanin pigment – usually dark feathers. A leucistic bird with different colors may show some colors brightly, especially red, orange or yellow, while feathers that should be brown or black are instead pale or white. Some leucistic birds, however, can lose all the pigment in their feathers and may appear pure white.
Albinism, on the other hand, affects all the pigments, and albino birds show no color whatsoever in their feathers. Furthermore, an albino mutation also affects the bird’s other pigments in the skin and eyes, and albino birds show pale pink or reddish eyes, legs, feet and a pale bill, while leucistic birds have normally colored eyes, legs, feet and bills.

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