The prodi-gull son returns

Ok, so this post isn’t about gulls, but it has been a long time since I’ve posted anything.  It’s time to break that streak and report on some new, fun things.  There are a few things that I’ve found, recently, that have really excited me, but the siting that brought me back in is this one:

These birds are new to my yard this year and have been coming back every day, now.  One male and two females.   They’re almost 2 weeks into their visit and all three have been regulars at the feeder.  They’re stocky birds, but a bit flighty.  Cardinals landing on the feeder will usually cause the Grosbeaks to fly back into the trees.

I’m doing everything I can to keep these birds happy and support them this year.  There is at least one report of Rose-breasted Grosbeaks using the same nest in successive years:

Friesen, L.E. et al.  1999.  Nest reuse by Wood Thrushes and Rose-breasted Grosbeaks.  Wilson Bulletin 111:  132-133.  

Now, we are at the southern edge of their breeding range (check out the USGS Breeding Bird Survey data) .   There aren’t so many reports of them breeding down here, but- fingers crossed- they’ll be back again next year.  The ‘Prodigrosbeak Returns’ just doesn’t sound quite as good, though.


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Jail-breaking snakes

photo 1photo 2Well, maybe smart is an overstatement. But not dumb is a good way to think about it. Today on campus, someone found a young Corn Snake in a building. Because…well…snakes are snakes, campus police got called to remove it. They brought the cute little thing over to the science building where it sat in a tank all day (snake prison).

Now this little snake is about as wide as a pencil and maybe twice as long. I went down to check on it (as a parole officer) and found it curled up in the corner of a 15 gallon fish tank. The tank was entirely empty, except for the snake…well, and the mesh cover that had a heavy bucket balanced on top. A bucket? For a snake that probably weighs about as much as a silver dollar (8g)?

Barnard, S.M., T.G. Hollinger, and T.A. Romaine. 1979. Growth and food consumption in the corn snake, Elaphe guttata guttata. Copeia 4: 739-741.

After checking on the snake, I went back to finish some things up in my office. When I returned to it, the little guy was checking out the edges of the mesh covering. It was both an amazing bit of gymnastics and an impressive way to evaluate its environment.

Now the quick version of the story is that I picked up the snake, put it in my lunch container (from which the lunch had been removed) and brought it home to release in my yard (pictures below). It took off quite willingly into the bushes when I set it free. The more fascinating part, though, is related to how that snake evaluated its environment. Lucky for us, people have studied this very thing in Corn Snakes.

Holtman, D.A.; T.W. Harris; G. Aranguren; and E. Bostock. 2008. Spatial learning of an escape task by young corn snakes, Elaphe guttata guttata. Animal Behaviour 57: 51-60.

What they found was that corn snakes are good at learning about their spatial neighborhood. By putting snakes into an enclosed arena with a lot of holes, but only one escape, they were able to see how snakes did at the task of finding the escape over multiple trials. Snakes regularly got faster (over 4 days) at finding the way out of the enclosure. This result means that 1) snakes recognize where they are and have memory and 2) they’re not just dumb reptiles. That little snake in the fish tank was investigating its enclosure and looking for an escape route. Had the bucket not been there (or had I taken too long to get back, it might well have Alcatraz’ed right out of there. Luckily for both the snake and everyone in the science building, the snake is now in my backyard, instead.

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Fireflies aren’t quitters

So I began this post with a simple observation in my yard tonight.  There are fireflies out and it’s raining.  It’s not a hard rain, but it’s definitely raining.  The fireflies (or lightning bugs) are still going at it, though, especially in the areas around the edges of my yard.  They’re really quite persistent (or maybe just desperate for love).  As I sat here pondering their search for a mate and the role of weather, I came across some other interesting information about these things.  Before I get to the science, though, I have to share some musings on fireflies.

First of all, fireflies (or lightning bugs) are beetles.  That makes them insects.  And that’s exactly where things get wacky.  I know a lot of people (my mother included) who hate insects and would never want one crawling on them, but fireflies (and ladybugs, I guess) seem immune to that kind of criticism.  People are generally fascinated by them.  Frankly, I have spent several evenings standing in place in my yard watching them.  I think my neighbors find me a bit odd (‘That guy is just standing there in the dark again, Mabel.’  ‘Close the door, Frank.’).

It is this sort of fascination that makes people more appreciative of these fun insects and so, here comes the science.  There are a number of studies looking at the timing of firefly displays around the world.  Partly, this array of studies is driven by people’s excitement of them (and their willingness to travel places to see them.  In the Great Smoky Mountains, predicting the firefly season was a project for researchers so that the National Park could give people notice about when the short firefly season there would likely get started.

Faust, L.F. and P.A. Weston.  2009.  Degree-day prediction of adult emergence of Photinus carolinus (Coleoptera:  Lampyridae). Environmental Entomology 38:  1505-1512.

Even more interesting is the amount of detail we know about some of the species of firefly (yes, there’s more than one species around here) and the amount of affection people have for them.  Lynn Faust says in the conclusions for her paper (Faust, L.F.  2010.  Natural history and flash repertoire of the synchronous firefly Photinus carolinus (Coleoptera:  Lampyridae) in the Great Smoky Mountains National Park.  Florida Entomologist 93:  208-217):

“No species can be properly conserved until it can be easily identified and its life history is known.  After 18 years of studying Photinus carolinus and a lifetime of appreciating their display as a thing of magic and beauty, I am constantly humbled by how much remains to be learned about this tiny bright creature.”

If that statement doesn’t just encapsulate why some of us love nature and do science, well…it does get it.  It’s a beautiful sentiment that really gets to the heart of what drives a field researcher.  Nature is always fascinating and beautiful.

But to her other point, why are people worried about firefly conservation?  Well, in part it boils down to the effects of humans. It’s not hunting (or even children with jars).  This time it likely has to do with light.  When people look at the factors that predict firefly activity, ambient light levels are the most important predictor (see studies above).  While there is evidence for a circadian rhythm in these animals, that cycle is entrained (which means that it is influenced by factors in the external environment- light!).

Dreisig, H.  1975.  Environmental control of the daily onset of luminescent activity in glowworms and fireflies (Coleoptera:  Lampyridae).  Oecologia 18:  85-99. 

In some places, though, especially around human development, ambient levels of light are not dropping as much.  Streetlights and neon signage keep light levels pretty high in some places and that turns out to be not-so-good for fireflies.  An increase in development leads to a decrease in fireflies.  Sigh.

Picchi, M.S., L. Avolio, L. Azzani, O. Brombin, and G. Camerini.  2013.  Fireflies and land use in an urban landscape:  the case of Luciola italica L. (Coleoptera: Lampyridae) in the city of Turin.  Journal of Insect Conservation 17:  797-805.  

In the end, I never did find a paper addressing changes in firefly behavior in the rain.  There may still be something out there.  I went down the typical internet path of (ooh, that’s cool, click on that link…).  I did learn that, though they may not be quitters, I’m going to help the fireflies in my yard out by turning off my outside lights.  Feel free to join me in the dark.





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Not even in withdrawal

One of the popular anecdotes associated with drug-induced hallucinations is the feeling of being covered with bugs.  Now I admit that I’ve had my share of bug-covered experiences (related to field work, not drug use), but it isn’t something that I actively search out.  I was looking out of my window today and watched two Brown Thrashers digging themselves into the dirt outside.  Now, that particular behavior could be the result of two different possibilities:  1.  Dust-bathing and 2. Anting.  Dust-bathing is a much more common sort of behavior.  In this process, a bird gets on the ground and gets dust in and among its feathers as a means of helping to get rid of parasites.  I’ve seen this behavior in a number of birds, but it usually involves a fair bit of movement, either rocking or actually jumping.  These two thrashers actually nestled themselves into the grass and then just sat without moving, not a typical sort of dust-bathing activity.  Occasionally, one of them would peck down into the dirt and then sit back down.  After the birds left, I walked out to investigate their little holes and did find some ants in them.  

Anting behavior is likely another way to clean.  The ants are invited (ok, they’re tricked) into climbing onto the bird and biting the feathers.  Why?  Do the birds actually enjoy the feeling of ants all over themselves?  Well, it’s actually more likely that the birds are treating themselves.  Ants, when they bite, release chemicals.  Some of these chemicals are quite potent and probably quite useful for the bird.  

Revis, H.C. and D.A. Waller.  2004.  Bactericidal and fungicidal activity of ant chemicals on feather parasites:  An evaluation of anting behavior as a method of self-medication in songbirds.  Auk 121:  1262-1268.

Ants are only one way to get these sorts of medicinal treatments.  Other people have reported birds using millipedes, marigolds and mothballs in much the same way.  

Clark, C.C.; L. Clark and L. Clark.  1990.  “Anting” behavior by Common Grackles and European Starlings.  Wilson Bulletin 102:  167-169.

Personally, I’d take marigolds and mothballs any day over letting myself get covered by ants and millipedes.  

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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.

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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.

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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