Sunday, October 30, 2005

Sharp-Shinned Hawk Age Coloration

I posted this on one of the larger nature photography critique sites, I'm posting it here partially to fill up some space, but also to fill in some of the natural history information available on this blog. Anyway, here it is, republished here.

Spent some time at Hawk Ridge this morning, and they had banded a nice succession of female sharpies, from 1st year to 3rd. Sharp-Shinned hawks are accipiters, woodland hawks that are very agile and feed on songbirds (although they've been reported to attack jays and robins - birds comparable in size to the sharpie). Males are about a 3rd smaller than the females, but coloring is pretty much the same.

First Year

First year plumage is readily apparent by the feathers on the breast with a more vertical pattern of color blotches that are more of a rusty-brown color. Feathers on the crown are mostly brown with some streaks of white. The shoulders are brown, with some gray, eyes and nares are yellow. Nearly 80% of Sharpies don't make it past the first year (starvation, predation, disease, window strikes, etc take a big toll).

Second Year

Second year birds show more of the classic accipiter color patterns like the breast coloration is more horizontally oriented and more of a ruddy brown, while the crown is slate gray with a little brown. Shoulders are a slate grey, with some hints of brown still visible. Note the iris is an orange color, while the nares are still yellow. Sharpies become sexually mature after 2 years, so this female may have hatched a brood this year.

Third+ Year

In the third year, the feather pattern takes the final coloration, and it's near impossible to specify the age after year 3. Note that the shoulders are gray and the crown a darker gray, the banding on the breast is a little more red and distinct. The eye, however, is what should grab you. The red color is well-developed now. Most Sharp-shinned Hawks live for about 10 years in the wild.

Hawk Ridge offers a nice little interpretive program to visitors during the fall migration, and for a donation, one can 'adopt' the bird: they get to release the banded bird and receive updates if that bird is ever spotted at other stations. Fall raptor migration is in full swing now, and for more information plus daily species counts, go to:

There it is, unedited as such, but the photos and info are the same. Sharpies are pretty much gone from my area, but I'm already looking forward to seeing them again.

Saturday, October 29, 2005

Tales From the Crypt: It's not just dirt, part I

Some of you may drive past something like this every day. To you, it might just seem like so much dirt near the side of the road, but to me it is a great deal more. The tan material shown in the photo is part of a Pleistocene (Ice Age) river terrace. How do I know it's Pleistocene? Well, perhaps that's a subject for another post. But suffice to say that in the Driftless Area (the area of Wisconsin, Minnesota, Iowa and Illinois that were not covered by the last glacial advance) contains buried treasure.

Treasure for someone looking for fossil land snails, at least. The material, complete with the remains of critters like land snails (even beetles) fills the river valleys as it washes in from the ridges and slopes above. These older river sediments are sometimes preserved in terraces like that pictured above. If one were to take a sample of that material and wash it through a series of sieves (down to .425mm) the remaining fraction might include fossils like those shown below:

What you see are the remains of land snails picked out of that very sediment shown in the top photo. Ostensibly, these critters washed into the valley from the ridges and hills above, but to what degree and how much downstream transport played a role is part of my Ph.D. dissertation.

Specimens in the above sample include: Discus shimeki (the larger helicoid shells). D. shimeki is known only as a pleistocene fossil in this area - modern populations are found at high elevations to the west. Columella alticola, another pleistocene fossil sometimes referred to as C. columella alticola, is one of the pupillid forms along with Vertigo modesta (yet another pleistocene fossil). Columella can be told apart from Vertigo quickly by looking at the body whorl as compared to the pentultimate whorl. The pentultimate whorl on Vertigo appears wider than the body whorl. There's one more pupillid hiding in that photo that I haven't keyed out yet. There is also some type of succineid, but without soft tissue, there's no hope of getting it down to species. The little round ball at the lower right is probably a snail egg.

Given how pristine these shells are (and the large number of intact eggs) it's not likely they were transported very far. I have other samples that do seem to have traveled. Perhaps I'll show some pictures of a well-traveled shell at some point. Just remember - to a Pleistocene paleontologist, it's always more than just dirt.

Friday, October 28, 2005

How not to do science, case in point.

MIT prof fired for 'faking' research.

Reminds me of a story floating around in some grad school circles about a mineralogist who 'found' a new mineral - by completely faking data.

Thursday, October 27, 2005

It's exactly like the Mel Brooks movie except it isn't...

Another image from today:

Vertigo sp. I am pretty sure I have specimens of V. modesta modesta in my samples, but here I'm not sure. I can make out two lamellae, but the others are either covered by sand, or indistict. Anyway, I think this is my second favorite snail from my collection (after Discus). By the by, that's Abe Lincoln's nose on the left.

I suppose I could talk about where V. modesta lives now and what that says about the climate in the Pleistocene, but I'll just say that it was colder. I think that's a fair bet. Once I get my assemblage data, perhaps I can talk about things in more detail.

it's like the festiva: a big smallness...

Just a test to see if what blogger does to one of my pics. The above pictured is Discus shimeki, wich has not [yet] been described in Wisconsin. I think I have good evidence to extend its range beyone Iowa - where the nearest pleistocene records exist. I hope I'm right on the species, as this would make my project more interesting. It does have the characters of shimeki where the ribs are indistinct on the lower surfaces, about 4 whorls, and the umbilicus seems right (pic to follow later).

I do invite any malacologist who sees this entry to correct me on the ID. For your info, the hash marks on the right are mm, and the umbilicus is 1/3 or less the total diamter (of about 6mm). I would have a pic, but the camera/computer setup I was using failed me and wrote a crapped-out CD where I could only use 2 images. Oh well.

Quals, vol. 1

This semester, I passed my qualifying exam. More of a formality than any real test, but it was still a lot of work. The format in the sed/paleo department at Madison consists of eight essay questions with an hour (sans notes) to answer the question. I'm going to try and put some of those questions and my answers up here in vain hopes of getting some comments from other paleontologists.

Anyway, here's the first in what may or may not be a series:

Why do some ancient lake deposits have diverse fauna that evolved through time, whereas in other deposits of similar duration the fauna appear less diverse and relatively static?

To fully answer this question would be a complete Ph.D. in itself. However, there are many factors that could play a role in the disparity between different lacustrine faunas. In a broad sense, there is a large body of evolutionary thought that holds the more stable an environment is, the more diverse the corresponding flora and fauna will be. And conversely, the less stable the environment, the less diverse the corresponding flora and fauna.

As an example, Lake Tanganyika contains more than 300 species of Cichlid fish, while nearby lake Malawi does not support nearly that many. So why are there so many cichlid species within Lake Tanganyika? The answer lies partially within its stability. It is a large, hydrologically open lake. Tectonic processes have kept it more or less open for the past several million years. Lake Malawi appears to have been more varied in its hydrology – and perhaps water chemistry.

An analogy would be the fauna found on tidal flats versus the fauna in carbonate reefs. Organisms that are tolerant of environmental extremes often dominate the tidal flats. The dramatic fluctuations in water level on a daily basis and the seasonal fluctuations of temperature and tide strength favor organisms that are generalists. These generalists can occupy several niches, and the intense competition for scarce resources keeps overall diversity low. The highly productive carbonate reefs, however, do not experience the seasonal extremes, nor the heavy tides associated with the flats. Instead, these environments are relatively stable, allowing organisms to exploit very specific niches. This specialization can reduce competition for varying niches, allowing a greater diversity of specialists within the same ecospace as compared to the tidal flats.

Another part of the explanation lies in the organisms themselves. Some organisms appear more prone to speciation than others. For instance, there have been relatively few species of lake sturgeon, despite it being a very long-lived group. Cichlids, by comparison, haven’t been around as long, but are an extremely diverse group. There is a group of cichlid fish that do nothing but feed on the scales of other cichlids. Within this scale-eating group of cichlids, there is one species with jaws that curve off to the side so that it can better grab scales off the body of a nearby fish. There is a separate species whose jaws curve the opposite direction, which allows them to more easily grab scales off the other side.

However, this “diversity” can be misleading. What the above example describes is phenotypic diversity – different physical forms, exploiting specific resources. There is another kind of diversity that can remain hidden from the observer: genetic diversity. Another cichlid example involves a group where the male grows very large and protects a harem of smaller females. The females hide in the empty shells of gastropods. Males will try to steal females from other males by taking the snail shells (complete with female resident). Larger males will have larger harems and produce more offspring. However, there is an alternate breeding strategy employed by some males of this species. Instead of being very large, they instead are rather small, and resemble the females. These males sneak into the harems of the larger males and mate with the females, right under the proverbial nose of the bigger males – thus making more of the small males. These are the same species of fish, with presumably low genetic diversity within the group but a high phenotypic (physical) diversity within the group.

Another example comes from the Green River Formation. Goniobasis tenera exhibits a great deal of variation in the decoration on its shells. Some are very subtle, with relatively flat whorls, and little sculpture. Others have very rounded whorls and prominent bumps and ridges on its shell. These are, however, the same species – and it is very likely they are the same species because nearly all pleurocerid gastropods (the family that includes Goniobasis) show this type of phenotypic plasticity. Goniobasis dominates the gastropod fauna within the Luman Tongue (or member, if you prefer) and several beds of the Laney Member. Viviparous sp. fossils are common in the Tipton Member, and one might be tempted to interpret the Luman and Laney units as being a longer-lived and more stable lake environment. However, the actual genetic diversity may very well be higher in Viviparous sp. from the Tipton than in Goniobasis tenera from the Luman or Laney.

Another reason might have to do with taphonomy. A lake with a relatively low sedimentation rate might have a high diversity of fossils within a lithologic unit, yet the fossils within that unit might not represent the actual diversity at any given time in the history of the lake. While a lake with a high sedimentation rate might only appear to have a low diversity: the abundant organisms separated by the relatively high volume of sediment dumped into the lake. These time-averaged deposits can make a low-diversity deposit seem abundant, and an abundant environment seem almost empty.

There are also biases in preservation – some organisms might be quite abundant, but contain relatively few hard parts to be fossilized. Shelled organisms dominate the described faunal character of the Cambrian, but how much of that is a bias in preservation. There is also a bias in perception (which partly plays into the genotypic versus phenotypic argument): much of paleontology seems vertebro-centric. Vertebrate fauna can appear at first glance to be more diverse than invertebrate ones, but most often the reverse is the case.

While it is likely that stable environments do often contain a more diverse fauna than unstable ones (even though the environments may account for a similar length of time), the actual diversity needs to be carefully considered. How much of the diversity is a bias, whether in preservation or the observer, and how much of that diversity is actual? For long-lived lakes, we can study modern diversity both on the phenotypic and genetic levels. For fossil lakes, such as Lake Gosiute, we are often left with searching for modern analogs and cannot separate the sedimentology from the paleontology. Only the combination of the two may provide a complete answer.

Wednesday, October 26, 2005

Once more into the breach dear friends.

This is my PhD. There are many like it, but this one is mine. My PhD is my best friend. It is my life. I must master it as I must master my life. Without me, my PhD is useless. With out my PhD, I am useless.

And so it goes...