Monday, June 28, 2010

Polish Swans and more at The Meadows

There are many reasons for wildlife enthusiasts to not be overly fond of Mute Swans, particularly in the USA where they are not native. Mute Swans are agressive towards other bird species (and towards people!), they do a lot of damage to native ecosystems and they have no natural predators in much of their introduced range. So it's not surprising that folks don't pay them much attention, except to say ahhh at the little fluffy youngsters. Because of all this, a lot of people are not aware that Mute Swans exhibit two color forms.

There is a recessive gene present in Mute Swans which produces two notable color differences to typical birds. This gene, which appears to be sex-linked to females, produces youngsters with pale, grayish-pink legs and white down. The leg color remains throught the individual's life, but the down of course is molted, after which the two forms become inseparable by plumage. Typical Mute Swans have gray-black legs and feet and, as youngsters, have gray down.

The origin of Polish Mute Swans appears to be a little obscure, but it seems that they originate from domesticated stock and the gene has been perpetuated in many populations by selective breeding by man in the past. Youngsters with white down, it seems, have a higher 'ahhh factor' than gray birds and were favored by owners of stately homes in Western Europe. Selective breeding also took place in Eastern Europe - within the native range of the species - and it is believed that the term 'Polish' was started by London poulterers who imported these specially-bred birds from Poland.

The incidence of Polish birds amongst North American populations of Mute Swans is surprisingly high and this probably suggests that Polish birds were favored by the original importers of the species. So, next time you drop into TNC's Migratory Bird Refuge on Sunset Boulevard, take a look at the (only) brood of young swans there and you'll see some Polish youngsters - though they're beyond the 'ahhh' stage and heading into 'Ugly Duckling' mode at the moment!

Today's lunchtime walk at the meadows also provided hopes of a promising breeding season for Least Terns, at least 30 Black Skimmers present, one Glossy Ibis and a busy flowering patch of White Melilot along the East Path which held at least 25 Red Admirals as well as Common Buckeye, American Lady, Black Swallowtail, Orange Sulphur and a number of busy dragonflies.

Polish Mute Swan family at TNC's Migratory Bird Refuge. Note the white down of the youngsters and Mom's pale feet. If the gene for white down is sex linked, as has been suggested, then it is perhaps surprising that this brood consists entirely of females. Incidentally, note also the extreme orange staining of this adult female on the head, breast and tail which comes from iron oxide in the water. [Photo by Mike Crewe]

Least Tern pair at the refuge lunch time today. [Photo by Mike Crewe]

Red Admirals display an amazingly complicated underwing pattern! Note the highly flexible proboscis probing for nectar in the little pea flowers of White Melilot. [Photo by Mike Crewe]

One of at least four Black Swallowtails along the Migratory Bird Refuge's East path today. To distinguish this species from Spicebush Swallowtail, look for the extra yellow spot, just inside the band of orange spots on the underside of the hindwing. [Photo by Mike Crewe]

Male Eastern Amberwing, one of several species of dragonfly on the wing at Cape May Point this week. [Photo by Mike Crewe]

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