Monday, January 24, 2011

John Blakeman on the Odd Buteo, Two Opossums in One Night and Opossum Tracks in the Snow

Yesterday's Odd Buteo

Ohio Red-tail Hawk expert, John Blakeman adds his expertise to the conversation-


The hawk in question is a partially leucistic Red-tailed Hawk, apparently still in its first year, as revealed by the very slightly elongated tail (Red-tail tail feathers lose a half-inch in the first molt). It’s not a Rough-legged Hawk, as the shape and wing patterning is all wrong for that species. All the other suspect buteos would be much darker. This is a Red-tail.

Leucisticism seems to develop incrementally in subsequent molts. The light coloring of the primaries of both wings is a typical pattern. In following molts, more and more feathers will come down white, often with streaks or patches of normal color, but distorted in shape. For example, when the whiteness appears in the red tail, the greater portions of the retrices (tail feathers) will be white, but often with a distorted, angled dark terminal band; or with white splashing at an angle across the partially-red feather.

It appears that leucisticism, which is not so uncommon in Red-tails, is expressed somewhat in the manner of gray hairs in humans, with age. I estimate it’s prevalence between one in 1000 to one in 5000, with the greater frequency more likely.

In this case, this an apparently young bird, with just the first hints of whiteness.

I trapped and studied an old, very wary formel (female) haggard Red-tail in 1970, and watched (before it was released) two molts. The bird got whiter each time. Before being trapped, she was the mother of a normally-colored tiercel (male) eyass that she and her normal mate successfully fledged.

Albinism or leucisticism is known in the other North American buteos, but it is very rare in those species. Just why the Red-tail has, and expresses these genes so frequently is a ponderable raptor biology question. I have no answers for it. The best explanation is that it would provide some hunting or survival advantage in snow. But if that were so, the trait would be seen much more frequently in northern birds. But that’s not necessarily so.

–John Blakeman

Thank you John, very interesting. The idea of albinism in Wisconsin being an adaptive advantage with all it's snow, makes sense, and it is the capital of Albinism in many species. There are quite a number of white deer here for instance. Though I understand some still have dark eyes so technically they're only partially albinistic. But you're right, if that is the case in RTHs why isn't albinism more prevalent in the north for that species?

Another mystery. :-) And another question to be filed in the mind waiting for the day something happens that might help answer it


7:12pm I looked out and WOW there's a possum right there on the step. The back story: I'd cleaned out the refrigerator and transferred the old food, but not too old food, all into a serving bowl that I was going to pour out on the goodie stump for the crows. I then left it on a counter while I went to another room.

In the meantime Quicksilver the African Grey Parrot had flown over and was helping himself. Greys have somewhat delicate digestion at times so I didn't figure even slightly old food was a good idea, being in the middle of something else, I took the bowl away from him much to his chagrin, (Don't worry he gets plenty to eat, but stealing food he is not supposed to have always makes it yummier), I opened the patio door, and put the bowl on the step to take to the stump later on when I had my snow boots on.

I forgot it. Thus attracting the opossum who as I watch starts wobbling the bowl around with his paw very vigorously. Bam, bam. The bowl is actually clunking on the concrete. OH NO! That bowl goes to a set of my mother's china that my youngest daughter is supposed to get. Beyond clunking on the concrete the bowl is very dangerously close to the edge of the step. That's a smash waiting to happen.

And even sending tidbits flying.

7:13pm Back to the bowl.

Is that bowl going to go over the edge? It looks like more than half is already sitting on air.

Here is a good view of the possum's back foot. Note the big difference with the front feet in the second possum photo above and the back foot in this photo.

By the way, the black blotch at the bottom of the photos is the cat Pyewackit's ear.

7:14pm Now you can tell it is the top of a cat's head. Pye waits for the opossum to reappear. He doesn't, so Pye wanders down to the basement hoping for an unenlightened mouse that has weaseled its way into the house.

Periodically she spends most of the hours of a couple days down there. Then suddenly she's back upstairs returning to her usual behavior. I believe she realizes there is a mouse in the basement, goes into mouser mode, eventually catches it, obviously eats it all as I never find any mouse bits, and then having done her duty or simply followed her irresistible instinct for obtaining a rodent meal-your choice, and then goes back to napping cat of sloth snoozing on the furniture until another mouse appears.

But back to those possums...

Several hours pass.

7:16pm Silver curious as to what everyone is looking at, flies down to take a look- flushing Pyewackit the Cat under the dining room table. The possum takes no notice as sight isn't their forte as a species. Note that Silver, having spotted the weird animal out there, has fluffed up his feathers into aggression mode. It makes him look bigger and he hopes scarier.

11:01pm She is following her nose to the bowl.

Possum circles round and while jockeying for a better angle, I accidentally bump the glass. Possum must have heard or felt the vibration as she freezes in place waiting to sense if anything else will happen, allowing me to get a slightly better photo of her in the dark.

She backs out.

Then she comes round the other side. 11 o'clock possum finishes up the food meant for the Goodie Stump. And Yea! The bowl is unscathed.

What about Possum prints? The front foot print is shaped like a long varigated toed paw but the back foot has a elongated print with a jog at the back with shorter toes which might appear strange until you know what it is. In case you're slightly confused by which way the animal is going, the back foot prints are going one way and the front prints the other.

The long trough in the snow is the print of the opossum's naked tail dragging behind her in the snow.

Donegal Browne


Karen Anne said...

I love opossums. The opossum(s?) who visit my deck thump the peanut dish around, too. I'm not sure what that's about.

The face of my visitor(s?) looks whiter than your photos, but I only see her(?) at night, so I could be wrong.

(Really needing number and gender non-specific words, and refusing to call animals "it.")

billnyc said...

Donegal Browne said...

Wildlife habitat? Art? Definite whimsy. I think someone should row out in a tux and play it.

Donegal Browne said...


Opossums are an ancient and amazing species. And as you know they are North America's only marsupial.

Likely your opossums and these are similarly colored. In natural light the Wisconsin opossum's coloration is not nearly as gold as they appear in these photos. They are more silvery than they appear here.
It was dark out with the only illumination a single incandescent bulb which shifted the white balance of the photographs. When I attempted to correct it things went a bit too blue. So I figured that a slightly gold opossum was better than a alien blue one. :-)