|
|
July 20th, 2010
Margaret Maciver photographed a leucistic White-fronted Plover at Cape Point back in 2008. Here’s her photo and note.
I found this leucistic White-fronted Plover at Olifanstbos near the Thomas Tucker wreck in September 2008. It was a very pretty bird, and seemed to be accepted by the other Whitefronted Plovers running around on the beach!
Thanks Margaret.
David Winter
July 18th, 2010
Gerrie Horn submitted these photos (originally via ECBirdNet) of a leucistic starling from the Eastern Cape. Any thoughts on what species it is?
Thanks Ken & Gertie.
David Winter
July 16th, 2010
I posted a note about a leucistic Speckled Mousebird at Grootvadersbosch a while back – you can read about it here. Tjaart Muller thinks he may have seen an albino or leucistic Cape Bulbul at Struisbaai. Tjaart posted the following photos and note on CapeBirdNet today:
I am new to the group and took these pictures in Struisbaai recently. Is it perhaps an albino, any info will be appreciated.
Wikipedia has this to say about leucism:
Leucism (occasionally spelled leukism) is a general term for the phenotype resulting from defects in pigment cell differentiation and/or migration from the neural crest to skin, hair or feathers during development. This results in either the entire surface (if all pigment cells fail to develop) or patches of body surface (if only a subset are defective) having a lack of cells capable of making pigment.
Since all pigment cell-types differentiate from the same multipotent precursor cell-type, leucism can cause the reduction in all types of pigment. This is in contrast to albinism, for which leucism is often mistaken. Albinism results in the reduction of melanin production only, though the melanocyte (or melanophore) is still present. Thus in species that have other pigment cell-types, for example xanthophores, albinos are not entirely white, but instead display a pale yellow colour.
More common than a complete absence of pigment cells is localized or incomplete hypopigmentation, resulting in irregular patches of white on an animal that otherwise has normal colouring and patterning. This partial leucism is known as a “pied” or “piebald” effect; and the ratio of white to normal-coloured skin can vary considerably not only between generations, but between different offspring from the same parents, and even between members of the same litter. This is notable in horses, cows, cats, dogs, the urban crow and the ball python but is also found in many other species.
A further difference between albinism and leucism is in eye colour. Due to the lack of melanin production in both the retinal pigmented epithelium (RPE) and iris, albinos typically have red eyes due to the underlying blood vessels showing through. In contrast, leucistic animals have normally coloured eyes. This is because the melanocytes of the RPE are not derived from the neural crest, instead an outpouching of the neural tube generates the optic cup which, in turn, forms the retina. As these cells are from an independent developmental origin, they are typically unaffected by the genetic cause of leucism.
Thanks Tjaart for the interesting photos and note.
David Winter
February 3rd, 2010
While birding at Grootvadersbosch Nature Reserve on Saturday I was surprised to bump into an albino Speckled Mousebird. The bird was seen close to the reserve office – see map below – and was very obvious amongst its grey team mates.
It wasn’t particularly obliging, but you get the idea from the photo below.
I gleaned the following from Wikipedia:
Albinism in birds is rare, occurring to any extent in perhaps one in 1800 individuals (Terres 1980). A bird that is albino (from the Latin albus, “white”) has white feathers in place of coloured ones on some portion of its body.
Four degrees of albinism have been described. The most common form is termed partial albinism, in which local areas of the bird’s body, such as certain feathers are lacking the pigment melanin. The white areas may be symmetrical, with both sides of the bird showing a similar pattern. In imperfect albinism, the pigment is partially inhibited in the skin, eyes, or feathers, but is not absent from any of them. Incomplete albinism is the complete absence of pigment from the skin, eyes, or feathers, but not all three. A completely albino bird is the most rare, lacking any pigment in its skin, eyes, and feathers. The eyes in this case are pink or red, because blood shows through in the absence of pigment in the irises. The beak, legs, and feet are very pale or white.
Completely albino adults are very rarely spotted in the wild. They are likely easier targets for predators because their colour distinguishes them from their environment. Falconers have observed that their trained birds are likely to attack a white pigeon in a flock because it is conspicuous. A complete albino often has weak eyesight and brittle wing and tail feathers, which may reduce its ability to fly. In flocks, albinos are often harassed by their own species. Such observations have been made among red-winged blackbirds, barn swallows, and African penguins. In a nesting colony of the latter, three unusual juveniles—one black-headed, one white-headed, and one full albino—were shunned and abused by companions. [more here]
What was very striking about this individual was how obvious it was in flight – at first glance it looked like a cockatiel! The photo below is a rather embarrassing attempt at a flight shot, but you get the idea.
Based on what Wiki says regarding albinism in birds, I would say this is a completely albino individual. Any thoughts?
Correction: it has since been brought to my attention that this bird is probably leucistic rather than an albino. You can read about the reasons here, but essentially the dark eye gives it away. A complete albino would have no pigment in the eye.
December 18th, 2009
Wednesday, a public holiday in South Africa, was spent birding with mates in the West Coast National Park. Located on the southern leg of Langebaan lagoon, the park is without equal in South Africa when it comes to the number and variety of shorebirds one can see. The Strandveld (local vegetation type) birding is also very good.
 There are three excellent hides located on the eastern shores of the lagoon. The older hide (northern hide) at Geelbek is, in my opinion, the best, while Seeberg hide comes into its own at high tide when gulls, terns and shorebirds roost on the sand banks. You need to time the tides quite carefully; the optimal time is either a rising low tide or dropping high tide in the morning (the sun will be at your back). High tide at either of the Geelbek hides is hopeless because there is no exposed mud; Seeberg is less dependent on tides.
 The northern Geelbek hide produced: Greenshank, Marsh Sandpiper, Little Stint, Curlew Sandpiper, Eurasian Curlew, Whimbrel, Ruddy Turnstone, Terek Sandpiper, Sanderling, Bar-tailed Godwit and Grey, Ringed, White-fronted and Kitlitz’s Plovers.
Interestingly, we spotted this partially leucistic Curlew Sandpiper. The photo is rather poor, but you get the general idea.
We only spent the morning in the park, but managed to notch up about 90 species – we limited ourselves to the southern section because we were atlassing that specific pentad for the South African Bird Atlas Project (SABAP2). Interesting birds for the park included Lesser Honeyguide, Common Swift (uncommon summer visitor) and Spotted Flycatcher (rare summer visitor in the Western Cape). Both the Lesser Honeyguide and Spotted Flycatcher were in the Spider Gums at the northern Geelbek hide.
The Lesser Honeyguide was actively hawking insects, so it wasn’t the best behaved photo subject…
Talking of subject behaviour, swifts in general don’t rank high. We saw a handful of Common Swifts through the morning, usually singletons. The above shot – as with all my other swift shots – was a fluke!
I’ve only seen Spotted Flycatcher once before in the Western Cape at Paarl Sewage Treatment Works (in 1993) so it was good to bag this one after a 16 year hiatus. This time gap is more a reflection of my lack of birding rather than the birds status. Our last stop for the day was the Abrahamskraal water hole, a good drinking spot for birds. Namaqua Doves are still very active in the park – I managed to snap this immature bird.
|
|
Recent Comments