Parental fatigue

When is it time for kids to go off on their own?  Certainly, what’s in the kid’s interest is not always the same as what’s in the parent’s interest.  In animal behavior, we call that “parent-offspring conflict”.  Everybody else just talks about it in the context of kids living in the basement.

This came up today because a colleague came in to my office to say, “there’s a hawk on the ground making a lot of noise!”.  In fact, that hawk (a juvenile Red-tailed Hawk) had been making a lot of noise all day.  Every time I walked outside today, I could hear it calling.  After my colleague mentioned it, though, I went out check out the bird.  This juvenile clearly didn’t relish being expected to fend for itself.

Now, after a hawk fledges, they remain with their parents for a period of time.  During this time, the bird is learning to forage on its own, but is still the recipient of food brought to it.  These hunger calls have been seen in birds from when they leave the nest until the point where they are completely independent, which may be 100 or so days.

Fitch, H.S., F. Swenson, and D.F. Tillotson.  1946.  Behavior and food habits of the Red-tailed Hawk.  Condor 48:  205-237.

Like most begging calls, these hunger calls are irritating (probably to the parents as much as to people) in part because of their desperate sound.   When I went to investigate this bird, it was no longer making calls, but was standing on the ground.  Apparently, this posture was what worried my colleague.  Watching the juvenile in this position was fascinating, though.  It repeatedly jumped onto a pine cone, then tilted sideways, several times tossing the cone into the air.  It would hop and land, talons splayed in the pine needles.  When other people approached the bird, it had no problems getting into the air and would land on branches nearby, then come back to its spot on the ground near the pine needles.  Several times it picked up an object in its beak and would then manipulate it with its talons, too.

These signs weren’t those of an injured bird.  Taken together, these behaviors seemed to beIMG_3464 that of a bird learning how to forage- very rudimentary hunting.  Even after all the high-drama screaming, a little bit of neglect from the parents gave this juvenile enough alone time to begin practicing itself.

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Key ears

It is a pretty iconic (and common) sound around Charlotte.  The keeyeeer of the Red-shouldered Hawk, that is.   There is a pair that has been really active in my neighborhood this year.  Red-shouldered Hawks are one of the birds that has taken really well to suburban habitats like Charlotte.  In one study of reproductive success, suburban birds had the same number of successful fledging events as birds from more rural areas.  It’s a useful thing to know about these birds- especially when paired with the information that nest site selection stays about the same.  Red-shouldered Hawks may nest in a variety of tree species, but on average, they prefer to nest in areas with high canopy cover and old trees (with wide trunks).

Dykstra, C.R. et al.  2000.  Nest site selection and productivity of suburban Red-shouldered Hawks in southern his.  Condor 102:  401-408.

Suburban Charlotte (which really is most of the city) definitely meets these criteria and so provides them with a great array of nesting options.   So keep your eyes and ears out for these gorgeous birds.  DSC_0404

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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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