Friday, October 03, 2008

BEWARE GLOBAL WORMING! And Is That Stacking or Copulation?

Earthworm with arrow pointing to clitellum
Courtesy of Great Lakes Worm Watch
Now why in the world is there a GREAT LAKES WORM WATCH?

Before you go too far into that thought, I'll let you know that there is also a Canadian WORM WATCH.

A while back I learned that our buddy the earthworm, friend of the vegetable patch gardener, item of fascination for small children, the one invertebrate that many people actually like, was an exotic. Yes, North America hasn't had any land based earthworms since the Ice Age. If we ever had any in the first place which seems to be under discussion. (Or if we only think they all got frozen out and we've got indigenous ones that we don't know about.)

The Earthworms that we have now seem to have came with the Europeans when they arrived with potted plants, horses, and previously dirt ballasted ships.

Now, when I realized that these earthworms were exotics and obviously invasive as they'd spread clear across the country in only a few hundred years, it seemed unique. I'd never heard any thing but good about earthworms from anyone. Unknown for an exotic that spreads. I mean people actually buy earthworms when there is a dearth of them in their gardens. So finally an invasive had arrived that perhaps was taking over an empty niche, doing lots of good, and no harm.

Silly me. I should know better. Well folks, here it is. Earthworms that invade a deciduous forest of hardwood trees, destroy the needed layer of organic "debris" that is necessary for the survival of herbaceous plants, like wild flowers, understory seedlings, tree seedlings, in three to five years.

How do the earthworms destroy it? They eat it all up. And when they eat it up, they destroy an incredibly complex microscopic ecosystem that is thought to have evolved without earthworms. Because when duff and herbaceous layers go, the forest begins to loose it's health as well as many of the formally numerous species that evolved along with and were part of the whole system.

Wait a minute you say, what about all the good stuff worms do? Like aerating the soil? Unfortunately a forest is doing swimmingly without all those worm holes. The worm burrows just cause nutrients to be leached down into ground water, as opposed to being available to the plants.

And you know all the good CO2 removal that forests do, cleaning up after us? A lot of that is done by the microbes and they're being eaten. Ditto, nitrogen grabbing.

The overpopulation of deer has been being blamed for the disappearance of wild flowers and understory from our forests. Maybe. But when the strata in which the plants grow disappears, having been eaten by earthworms, so does the herbaceous layer. The deer are just a whole lot more obvious about being there, than the worms are.

Here's the deal. There is another call out for Citizen Scientists. As Cornell has done previously with Pigeon Watch and Feeder Watch, when information was needed from many micro locales over a broad range. The Worm Watches want to know which species of worms are currently where, when they begin to broaden their range, or change species proportion. That's a tall order when you think about it because they aren't just dipping into a ready made population who already participates in the activity--The people who watch pigeons or watch their bird feeders and can tell the difference between species or color morphs.

Beyond the Great Lakes Area which isn't exactly small, Canada is attempting a National Survey, and Canada has a lot of square inches that could be inhabited by earthworms.

I don't know about you folks but I've never done a lot of species identification when it comes to earth worms, have you?

Well, here's your chance if you're up for it. Learn the most common species of worms--

Key to Reproductively Mature Earthworms

Plus tidbits such as a worm, with a bright orange clitellum, is in heat.

Then there is learning the sampling methods--Flip and Strip, Modified Flip and Strip, and Modified Hand Sorting.

And Great Lakes Worm Watch was looking for partner organizations so Minnesota Worm Watch was created. They send their data to the larger organizations.

And they'll tell you how to create a partner organization to investigate, fill in data sheets, and send it in, basically to CONTAIN THOSE CRAWLERS.


Photograph Courtesy of Charles Juels

Sally wrote in the comments section,

I wonder if those Harris's hawks are actually stacking, or about to copulate? Perhaps coincidence that the male happens to be on top? I have had no luck finding photos of stacking behavior, either.

Hi Sally,

It is tough to find photographs of stacking, isn't it?

I assume part of the problem is that stacking is undertaken usually, only when there is a lack of enough high perches for all members of the family group to stand on.

Where is the lack of high perches most often a problem, while still allowing a viewer to see them do it? In the desert, and that's where stacking takes place--a largely unpeopled environment. Which also means that humans who are there, are easily seen by the hawks who then likely, take off for unhumaned horizons. So even though a human may catch a stack with the eye, there is also the time it takes to pull out the camera and get the shot.

As to whether this could be a pre-copulation photo, I don't think so.

Ordinarily, a female hawk "invites" the male for copulation by leaning forward and tipping up her posterior, placing her cloaca in an easier-to-access position. Upon the males arrival she also will switch her tail to one side. And males during copulation are much further back in relation to the female. They also use the flapping of their wings to remain in the proper tipped back position so they can be cloaca to cloaca with the female.

I've never seen any species of bird copulate, who's start up position for copulation is standing on the female's back, nor is that an "after" position.

I think he's standing on her back for a better view of the hunting area. If you look at the photograph they both seem to be looking at the same thing

In reference to who is on top--the literature says that the higher status or dominant bird is on the bottom. The less dominate will give up his current perch when a more dominate bird comes toward it, every time. Therefore the the closer to the bottom the more dominate the bird.

Now I have seen young Red-tails fresh off the nest, knock their mothers off a perch but I'm figuring that's most likely inadvertent or if it isn't she's giving them some slack as they've yet to learn proper Red-tail manners. I doubt she'd let them do some months down the line.

Is the female always the dominant bird in a raptor pair? Or is it really the most dominant bird on the bottom, or just the biggest one?

Is the biggest bird always the most dominate?

If, there were two, two year old progeny also in the group, (Harris Hawks don't go out on their own until three years of age.), one male and one female, would it always be the young female who stood on Dad? She'd be bigger than he is, but I imagine Dad would still be higher in status than the daughter.

What would answer the question? A photograph of three Harris Hawks in a stack of two females and one male.

Pending enough size difference to know, of course.

And we had quite a hard time finding any photos of a Harris stack, until Catbird found that one.

But I'm going to keep looking and I hope you will too.

Donegal Browne

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