Get out of my yard, you pesky kids!

And so it’s begun.  A few nice warm days around here and the bird activity changes really dramatically.  I was running through the neighborhood this morning and there was quite a ruckus happening in the yards of a few people.  I watched a pair of male Northern Cardinals chasing each other through trees and bushes, all the while calling at each other.  I did see one female hanging out off to the side, but she really stayed out of the altercation.  These males went around the front yard of this house for several minutes, before one of them flew across the street.  On landing in a tree in that yard, he was promptly attacked by another male who flew out of the bushes.  This fight didn’t last long at all.  The one who came out of the bushes was a much brighter male (I’ll come back to the color part in another post), and drove the other one away quickly.  The escaping male once again flew into another yard where it was attacked by a fourth male.

Each of the males who was protecting a yard remained visible while that poor little male moved down the street.  I was actually enjoying these little battles, but it got me wondering about a couple of things.  Firstly, I was sort of amazed that there were so many established males in that little stretch of street.  Apparently, cardinal territory size is quite variable.  Territories with a lot of shrub cover tend to be smaller than those with mainly trees.  These yards definitely had a lot of landscaping and so may actually have favored smaller territory sizes.

Conner, R.N.; M.E. Anderson, and J.G. Dickson.  1986.  Relationships among territory size, habitat, song, and nesting success of Northern Cardinals.  Auk 103:  23-31.

Now, given that I was actually out running, I was willing to stop and watch these birds for a little bit, but I did lose track of the male who kept getting chased away and finally got back to running.  It did make me wonder, though.  At the first yard, was that male actually trying to establish himself on a territory or was he trying something else?  In lots of animals, there are many different sorts of mating tactics (we call them alternative mating strategies).  I arrived when the fight was already in progress.  What is that male was actually trying to sneak in a little tryst with that female?  In many species, young males who are unable to acquire or defend territories on their own become floaters.  This strategy means that they move around, between and (furtively) within the territories of other males.  Sometimes these males get secret matings with females.  Sometimes, this experience may actually help them learn the skills and the area better so that they can defend better quality territories in future years.

Zack, S. and B.J. Stutchbury.  1992.  Delayed breeding in avian social systems:  The role of territorial quality and “floater” tactics.  Behaviour 123:  194-219.

If that’s what he was doing, he was certainly getting in some good practice today.  I expect great things from that bird in the future.

Posted in birds, ecology, mating | Leave a comment

Late night sprints

Oh you don’t know how hard it is to resist the allure of reinvigorating a powerful internet meme!  You’ll see why soon enough…

Last night I gave a little talk on birds down in South Carolina.  I was driving back home around 9 down a fairly dark road.  During the day, I think there is quite a bit of traffic on this highway, but at night, it was pretty empty and there wasn’t much in the way of additional lighting.  Out of the corner of my eye, I did see a little blob moving sort of quickly.  I slowed down the car a bit and watched that little blob pick up speed and sprint through the shine of my headlights.  It was a Red Fox.  The bushy tail and dark patches on the ears and tail were distinctive, even in that light.  I was sort of amazed to be able to get such a nice view of it, even if it was at 40mph.  That little fox, though, really upped its speed quite a bit, which made me wonder a couple of things:  1.  How fast do they go?  and 2.  What was it doing out there in the middle of the road?

The first answer is easier to find. People have studied various aspects of the speed of all sorts of animals for a long time in order to understand some of the mechanics of movement.  I found one record for maximum speed in the fox listed as 42km/h (~26mph).

Heard-Booth, A.N. and E.C. Kirk.  2012.  The influence of maximum running speed on eye size:  a  test of Leuckart’s law in mammals.  Anatomical Record 295: 1053-1062.

The second question is much harder to address. It’s like the perpetual chicken question.  Why did the fox cross the road?  Well, maybe there really was something on the other side.  Or maybe competition with other foxes or with coyotes was driving it to change food resources.

There is evidence that foxes are quite good at shifting resources in the presence of competition from coyotes.  It’s quite possible that this little fox was out foraging in the night looking for some of the smaller mammals that advantage of some of things that end up along road sides.

Theberge, J.B. and C.H.R. Wedeles.  1989.  Prey selection and habitat partitioning in sympatric coyote and red fox populations, southwest Yukon.  Canadian Journal of Zoology.  67:  1285-1290.  

So, in the end, the only way to answer question #2 for certain would have been for me to follow that fox.  With those speeds, though, I would have been hard-pressed to chase it through the shrubs on the side of the road.  I guess I’ll just have to keep wondering what does that fox eat…

P.S.  I couldn’t resist the power of the meme.

Posted in ecology, foraging, mammals | Leave a comment

Here’s to you, American Robin(son)…

Ok, that title is pushing it a little bit.  It’s been a long day and the Simon & Garfunkel reference made me smile.  But the robins have been on my mind of late.  Last week, a bunch of people asked me about the groups of American Robins that were flying in and out of the big holly bushes on campus.  When I walked outside, I saw huge numbers of these birds perched in the oaks, on the ground, and flying back and forth into the bushes.  Even from a distance, it was possible to see the brightly colored berries disappearing from the bushes.  In just a very short little video (filmed with my phone, so don’t expect much), you can see just how active these birds were (and if you look closely, you can see the fruits disappearing!

Now, since I had so many people marvel at these robins and all their activity, let’s hit this observation from a few different angles:

1.  What were they doing?

2.  Why so many?

3.  Was Simon & Garfunkel really necessary?

Ok, number 1.  What were they doing?  Well, the birds were clearly eating the fruits!  Throughout the fall and winter, American Robins rely heavily on fruits for the largest portions of their diet.  Winter fruit resources do tend to be fairly spottily distributed, so having lots of individuals foraging on a single ripe tree isn’t so surprising.  Additionally, from the holly’s perspective, it’s a great way to get your seeds dispersed.  The sidewalks (and driveway, and peoples’ cars) around that area were covered in robin poop that was full of seeds.

2.  Why so many?  Well, around here, some of our robins are winter residents.  They breed here and stay here year-round.  A lot of the robins that are here now, however, are migrants who have come down for our balmy winter to escape the frigid north.  Cold weather is a stressor on birds and they may gather in larger numbers in trees at night to insulate themselves against the cold.

Walsberg, G.E. and J.R. King.  1980.  The thermoregulatory significance of winter roost-sites selected by robins in eastern Washington.  Wilson Bulletin 92:  33-39.

In smaller groups, a robin might actually try to defend these fruit resources.  That defensive behavior has been observed with a single American Robin successfully driving off flocks of up to 15 Cedar Waxwings.  The authors do point out, though, that in groups larger than 15, the robin was unable to protect the fruit.

Pietz, M.A.J. and P.J. Pietz.  1987.  American Robin defends fruit resource against Cedar Waxwings.  Journal of Field Ornithology 58:  442-444.

So, onto #2.  Clearly with such a large group of robins, no single individual could defend the resource.  As a result, we end up getting a free-for-all of feeding.  Birds just rushing in and out of the bushes (and pooping all over) in order to stock up on the fruit.   The Walsberg and King paper talks about flocks in Washington of usually 20-40 birds.  But they do mention another paper that describes an entirely different sort of flock in Arkansas.

Black, J.D. 1932.  A winter robin roost in Arkansas.  Wilson Bulletin. 44:  13-19.  

He describes a roosting site spread over quite a large area and containing upwards of 250,000 birds!!!!  Uhm…wow!  Now that is a flock!  It makes the 100 or so birds on campus kind of boring.  250,000?  Here IS to you, American Robin(son)!!!

#3.  See?  Absolutely necessary.

 

Posted in birds, ecology, foraging, migrations, thrushes | Leave a comment

A crown of gold

If you’ve watched (or read) any of “Game of Thrones”, then you’ve got a pretty good image of that crown of gold.  There is, however, a little crowned bird that’s flying around here without any of the pain of Viserys (and without the drama, too!).  It is the Golden-crowned Kinglet.  I was hiking with a friend up at Crowder’s Mountain right around Thanksgiving (yes, this is a late post) and saw one foraging in the trees.  Now these little birds are migrants, doing their breeding up in Canada and the northern U.S. and moving south during the winter.

Walking through the woods here, in winter, they don’t look that luxurious- bare branches and dried leaves blowing around.  But to a bird that weighs about 6g (0.013lbs = .21oz) it must be heaven compared to what it’s like up in Alberta!  Unlike the Ruby-crowned Kinglet, which catches its food on the wing, the Golden-crowned is a slower-moving bird.  They use their grooved feet and longer toes to hang from branches and gather insects from the foliage.

Keast, A. and S. Saunders.  1991. Ecomorphology of the North American Ruby-crowned (Regulus calendula) and Golden-crowned (R. satrapa) Kinglets.  Auk 108: 880-888.

While lots of the trees up on the mountain are rather barren, there are still a number of pines and holly that probably provide all sorts of good foraging (and roosting) habitat for these birds.   Roosting sites are important for birds of this size, too.  When you’re a bird that’s only 6g, keeping warm is not an easy challenge.  Good, clean feathers are important, for sure.  Golden-crowned Kinglets, in winter, have an additional trick they use to keep warm.  They huddle.   Groups of birds that forage together will stop feeding as darkness settles in and gather together in groups.

Heinrich, B.  2003. Overnighting of Golden-crowned Kinglets during winter.  Wilson Bulletin 115:  113-114.

So, while Homer may have been right that “Too many kings can ruin an army.”  It would seem that a good many kinglets can keep you toasty.

 

Posted in birds, ecology, foraging, warblers | Leave a comment

A bit of death in the morning makes for a good meal

Over the holidays, I was visiting Virginia and while out running with my sister, came upon a lovely smell.  Well, actually, before we smelled anything, we saw the vultures.  Right on the side of the road was a group of them- 4 Black Vultures and a Turkey Vulture off to the side.  Up in one of the nearby trees was another Turkey Vulture just keeping an eye on things.   As we moved in closer to get a better view of things, the Black Vultures lifted up their heads and turned their bodies away from us, but didn’t fly off, they just sort of got prepared.  Now, why anyone would bum rush a vulture, I don’t know, but they were ready for us, anyway.

It was, at about 30 feet, that we could smell the carcass.  Half-buried under the leaves was part of a deer.   I couldn’t see what the damage was, but I’m guessing it was car-related.  The actual death, however, is beside the point.  The cool part was the vultures.  As we initially approached, the 4 Black Vultures were the ones that were clearly on the carcass.  The Turkey Vulture that was on the ground was at least 10 ft away from where the body lay.  These are the dynamics that I find the most interesting.

Turkey Vultures are probably known best for their sense of smell.  Unlike most birds, Turkey Vultures have a good one, though it probably works best relatively close to the ground.  In conjunction with that sense of smell, they have a comparatively light body to allow for slower (and lower) flight than other vultures which could explain why Turkey Vultures are usually the first birds to arrive at a carcass.

Wallace, M.P. and Temple, S.A.  1987.  Competitive interactions within and between species in a guild of avian scavengers.  Auk 104:  290-295.

Another interesting point that comes out of this article is that in one-on-one interactions, Turkey Vultures will usually successfully drive away individual Black Vultures from carcasses.  The unfortunate part of that statement is that it is restricted to one-on-one interactions.  Black Vultures, unlike Turkey Vultures, rarely seem to forage alone.  They do rely on foraging groups.

Rabenold, P.P.  1987.  Recruitment to food in black vultures:  evidence for following from communal roosts.  Animal Behaviour 35:  1775-1785.

This group foraging behavior can give them better abilities to find food and also increase their competitive advantage at a carcass.  Turkey Vultures who find small carcasses can access food quickly, before Black Vultures arrive.  Once Black Vultures do find a large carcass, they will commandeer it and drive off the Turkey Vultures.  Black Vultures are more likely to return to carcasses several days in a row, while Turkey Vultures tend not to return.

Buckley, N.J.  1996.  Food finding and the influence of information, local enhancement, and communal roosting on foraging success of North American Vultures.  Auk 113:  473-478.  

So what we saw that day, was (probably) a recently killed deer that had been spotted by the Turkey Vulture and taken over by the Black Vultures.  Sadly, in the few minutes that we watched the birds, the Black Vultures seemed to have no interest in sharing with the Turkey Vulture.  The holiday spirit, apparently, doesn’t extend to dead deer.

Posted in birds, communication, ecology, foraging, raptors, vultures | Leave a comment

Birding with microscopes…?

While normally I spend my time looking at big animals, there is a whole world of other things out there.  Last month, I was playing around with some water samples from Little Sugar Creek, just trying to see what was in there and came across this little guy (or girl or neither).  IMG_1533

This little thing is a Rotifer, a very small animal.  It belongs to something we call the meiofauna, though they’re often small enough to be seen only with a microscope.

They are cool, little animals and remarkably complex for something so small.  First of all, they may make up to 90% of the life in the plankton in freshwater areas.

Ricci, C. and M. Balsamo.  2000.  The biology and ecology of logic rotifers and gastrotrichs.  Freshwater Biology 44:  15-28.

 

This little animal is why I enjoy doing the things I do.   These little animals are common as dirt (well, maybe not quite that abundant, but they’re all over the place) and no one even knows them or recognizes their importance.  As a small filter feeder, these little animals are taking in smaller microorganisms and bacteria.  Ecologically, that means they’re really quite important participants in freshwater environments. In fact, people think that rotifers might be good ecological indicators of the health of freshwater systems.

Gannon, J.E. and R.S. Stemberger.  1978.  Zooplankton (especially crustaceans and rotifers) as indicators of water quality.  Transactions of the American Microscopical Society 97:  16-35.

Does that mean Little Sugar Creek is in good shape?  A couple of rotifers isn’t enough to answer that question, but it is a good start.

Posted in ecology, invertebrate | Leave a comment

Oh snap!

Walking along Little Sugar Creek one day, something flashed and caught my eye in the stream.  It was the shiny underbelly of a fish that was probably 8 or 10 inches long.  The weird thing about this fish was that it was moving completely sideways rather than headfirst.  As I got closer to the fish and could see through the murky (it wasn’t so clear that day) water, I could see the problem.  There was a good-sized snapping turtle carrying that fish.  I watched it for awhile until it climbed under some rocks under the bridge at East Boulevard.
IMG_1491One of the things that struck me about this turtle was that none of its movements were very fast.  Even underwater, it slowly pushed itself along the rocks, pausing from time to time.  A swimming fish is definitely faster moving than anything I saw that turtle do.  I know that snapping turtles are sit-and-wait predators.  Rather than tracking and chasing prey, they hide and grab it at an opportune moment.  For a turtle, there are still two issues with this kind of hunting:  1.  The prey grab has got to be faster than the reaction time of the fast moving fish and 2.  The problem of water.  Water is, unfortunately (depending on your perspective) viscous.  When you push yourself forward in the water, you push the water in front of you away, which can make it hard to grab things (try pinching a fly out of your drink!).  A snapping turtle that pushes its head and mouth forward to grab a fish would also push the water and so, push the fish out of its way.  So how does the turtle manage this?

Well, now we get to the fun bits about mouth parts.  In order for a turtle to get prey into its mouth (and avoid warning prey about an impending attack), it needs to reduce the movement of water forward.  The only good way that a turtle can do this task is to pull water into its mouth.  In a fish (with gills), water can be brought into the mouth and expelled through the gills, creating a great degree of suction.  A turtle can’t do this kind of displacement, though.  What a turtle can do, however, is to drop its tongue in its mouth and expand its throat.  With this movement, a turtle can ram its head forward (at 150 cm/s) without pushing its food out of the way.  Cool stuff.  Slow body, but very fast (and flexible) head.  Snap!

Lauder, G.V. and T. Prendergast.  1992.  Kinematics of aquatic prey capture in the snapping turtle Chelydra serpentina.  Journal of Experimental Biology 164:  55-78.

Posted in foraging, predation, reptiles, turtles | Leave a comment