Thursday, August 21, 2014

Allie's project: What did she say?

 My name is Allie Burnett and I am an undergraduate at Michigan State University in Zoology. This summer I returned to KBS to work on another project related to Cara's research.

When I first started studying birds, I found the varying types of songs and responses to these songs interesting. I wanted to know what these birds were "saying" to each other and what determined which type of song was used. The discovery of female song in our House Wren population intensified this curiosity, especially since female song is unexpected in temperate zone House Wrens. The huge difference in responses to various female songs supported the idea that each song was communicating something specific to the recipient. Perhaps these females, who responded most aggressively to other female song, were using songs to communicate and compete with rival females. One of the most important things to communicate to a rival female is something that will influence the outcome of a fight, such as physical condition. We knew from prior experiments that specific song characteristics elicited greater aggressive responses; did these song characteristics also correlate with physical characteristics of the female singing them? In order to find this out, we spent the summer recording songs and gathering physical measurements from each female. After hours of song analysis, we found that female condition does influence female song. Not only did females of higher condition sing a greater variety of songs, but they also sang more notes per second and a higher percentage of a syllable named "R." These characteristics were the same ones that elicited high aggressive responses. These results lead me to further question why females of higher condition sing differently. It is possible these females can afford to sing songs that elicit more aggressive responses in order to obtain resources. Alternatively, maybe these song characteristics elicit such aggressive responses because they are more likely to be sung by a high condition female, and therefore a much larger threat. Only more research will be able to tease apart the secrets of female song.

Friday, August 15, 2014

Animal Behavior Society Conference

The Getty lab just returned from the annual Animal Behavior Society Conference held at Princeton.  We had a strong showing this year.  I gave a short talk on the relationship between female aggression and offspring performance.  I've found that more aggressive females have heavier babies.  In many birds, the heavier your babies, the better the chance they have at surviving.  This is an important finding because it could be a way that female aggression evolved in female house wrens.

A blurry picture of me from the audience of my talk

The other members of the Getty lab presented their latest findings too.  Sara presented a poster on her work on how growing up with or without your siblings changes your growth and development in tree frog tadpoles.  Michael also had a poster on his work on whether aging or physical condition changes the risks tree frogs are willing to take when finding a mate. 

Michael's former URA and current research assistant, Levi, joined us and presented a poster on a project he did with Michael.  Levi found that poor condition male frogs are willing to take more risks when they think predators are around in order to attract females.  Levi's poster was so good he won the Genesis award for the best undergrad poster at the whole conference!

Monday, August 11, 2014

Undergrad Research Symposium

Half of science is communication.  The results of your experiments don't mean much if you never tell anyone about them.  Scientists share their results through articles in scientific journals, talk to various audiences, and poster sessions at scientific conferences.

The undergraduates at KBS celebrated the end of their field season with a poster session.  Each undergrad made a poster about their project and then explained them to visitors as they filtered through the room.  Both Aaron and Allie's posters came out beautifully.  Allie's poster explained how certain things about a female's song may communicate her fighting condition to female rivals.  Aaron's poster showed how female house wrens can use their egg color to tell males they are in good condition.

Monday, July 28, 2014

Aaron's project: What's in an egg?

 My name is Aaron Aguirre and I am an undergraduate at Michigan State University studying Fisheries and Wildlife. This summer I was lucky enough to be Cara’s assistant as she conducted her research.

As part of helping Cara with her work, I was also responsible for developing my own topic of study and designing an experiment to conduct throughout my time here. Delving away from bird songs and calls, I decided to put more of a focus on the other ways in which house wrens communicate with each other.  Something Cara had said to me sparked my curiosity in the eggs of these birds. She told me that the last egg of a female’s clutch will often be much lighter than the others because male house wrens seem to be attracted to lighter eggs and more willing to invest in caring for them. After collaborating with Cara I decided to study if the brightness of a female’s eggs relates to their physical condition as well as if stress on the females will affect the brightness of their eggs. 

 Above: An example of the photos Aaron used to collect data on eggs.  As you can see above, the last egg is often brighter than the ones before.  A previous graduate student in the Getty lab, Lindsay Walters, studied the connection between egg color and male investment.

My interest in this topic stems in a similar way from why Cara is studying house wrens. When people think “bird communication,” they will probably think about the multitude of bird songs and calls they hear in the early morning. Similarly, most will think that male song birds are the gender that are competing and proving themselves to the females; a nice song tells the female that a male is in high condition worthy of being their mating partner. This is why I find my topic to be so interesting; it is the unexpected. By looking at the eggs, I am seeing how females are communicating to the males and how they show males that they are physically fit and worth investing time and energy into ensuring the success of their offspring.

Thursday, July 17, 2014

This season by the numbers

  Despite the population being roughly half the size of a typical year, we've accomplished a lot this season so far!  So far there have been 33 females and 34 males at our field site (that we know of).  All but one are currently banded.  We've collected 77 blood slides and samples from these birds and run 98 aggression trials.

These females have been busy.  They've laid 266 eggs (and they're still going!).  We've measured all and photographed most.  159 eggs have hatched and 82 of these offspring have successfully fledged.  We've measured babies 524 times and there are many more still to come!  

Sunday, July 13, 2014

Nature and Nurture

What makes you who you are?  The color of your eyes or the shape of your nose come from the genes you inherited from your parents.  Something like your personal beliefs come from your social and cultural environment.  However many things, such as your risk of developing a particular disease, are influenced by both your genes ("nature") and your environment ("nurture").  Scientists studying animals must keep in mind the influences of both nature and nurture when studying a particular trait or behavior.

We've found in previous years that more aggressive house wren moms have bigger babies.  Why is this?  We know more aggressive moms don't feed their babies more often (at least as far as we've observed).  Maybe aggressive females have genes that produce bigger babies.  Maybe they lay eggs with more hormones that make babies grow faster.  Maybe they are better at foraging for high quality food or they interact with their babies in some other way that promotes growth.

To try to disentangle the influences of nature and nurture, this summer I'm doing a "cross-foster" experiment.  This is common experimental approach where scientists swap eggs or babies between nests.  Birds like house wrens treat anything in their nests as their own offspring.  This allows scientists to look at the influence of one genetic background in a different social environment.  This summer we're swapping some clutches before incubation starts.  If more aggressive females have genetic offspring that are bigger, the cause is likely in the genes or in the eggs.  If more aggressive females instead have bigger social offspring, the cause is likely something in the environment or the female's behavior.  However, the answer may be somewhere in between.

   Two clutches that were swapped earlier this summer

Saturday, July 12, 2014


11-day-old baby nestling
Raising baby house wrens is hard work.  After a ~7 day egg laying period and a ~12 day incubation, the house wrens hatch and start growing quickly.  The babies gain around a gram each day, reaching adult weight in just 10 days!  By day 18 they can fly and look just like adult wrens.  This is a lot of work for the females.  Not only does she help the male feed them every several minutes throughout the day, but she cuts down on her feeding time drastically when she is incubating and may lay 2 or sometimes almost 3 times her body weight in eggs during the season.  Whew!
One of the explanations for why females are generally less aggressive than males is that aggression interferes with reproductive demands on females.  This trade-off exists for some males.  The Ketterson lab has found that  male juncos given testosterone implants (the hormone linked to aggression in males) are not as good at feeding their nestlings.  We don't know yet if testosterone is responsible for aggression in female wrens.  Regardless of the hormonal mechanism, fighting with other females could take time and energy away from the busy work of raising babies.  
I originally predicted that more aggressive females would have smaller babies.  However, I was surprised to find that babies from aggressive moms actually end up bigger!  In other migratory bird species, the size of the nestling at fledging has a big impact on it's chances for survival.  If these babies have a survival advantage and aggression is passed down in house wren genes, female aggression will continue in the house wren population.     


The baby osprey are getting close to fledging.  The house wrens are already well into their 2nd brood, but the osprey are just finishing their first.  It takes a lot more food to make a baby osprey!  There are three babies in this osprey nest, although one is significantly smaller than the rest.  You can see one of the babies on the left side of the nest in the pictures below.

Some larger bird species frequently lay one more egg than they can typically raise successfully.  This extra egg acts as an insurance policy.  Usually this baby is too small to compete with it's siblings.  However, if something happens to one of the larger babies, the parents still have a chance to reproduce.  If it's a particularly successful year, the parents can raise an extra baby!

 The male osprey comes in for a landing
One fledgling on the left, adult female in the middle, and adult male on the right

Friday, June 13, 2014

Welcome, Allie!

We're very happy to welcome Allie back to the wren project this summer!  Allie is an MSU zoology major Allie who was my URA during the summer of 2012 when I was first starting out.  Now she's back to do an independent project looking at female house wren song.  You can see her decked out in recording equipment below.  Female house wren songs show lots of variation between individuals.  Allie is trying to figure out what these songs might be communicating to rival females.  Stay tuned for more news on her project!

Allie is excited about recording females

Spectrogram of the song from the female rd/pu, or/al at 11.  Spectrograms are read sorta like music- notes higher on the y-axis are higher pitched.  Darker spots are louder.  11's song is reminiscent of the first song I ever recorded.

Tuesday, June 3, 2014

Disappearing Females

Bk/wh, gn/al's first attempt at polygyny was short-lived.  This morning all the eggs in his second nest were gone (perhaps illustrating the disadvantage of sharing a mate)!  You can see a picture of this nest below.  This is one of the frustrating cases where we're not sure exactly what happened.  Usually when a predator get's the eggs, they disturb the nest in some way.  This nest had some new sticks near the front and no evidence of the eggs either in the box or on the ground.  New sticks are usually a sign that either a new male has moved in or the male lost his female and resumed building.  I spotted bk/wh, gn/al on this territory today, but there was no sign of a female.  The next couple days could reveal what happened.  If there's a new egg or evidence of substantial female building tomorrow, this was likely a female replacement.  If there are no female signs tomorrow, it will remain a mystery.

Nest at A3.  Empty nest cup is at the back, new sticks are near the front.

Sunday, June 1, 2014

Polygynous Males

Today we confirmed that the first male to arrive (bk/wh, gn/al) has attracted a second female!  The house wren mating system is classified as "facultatively polygynous".  This means that most of the time they are socially monogamous, pairing with just one mate (though often mating with many more!).  However, given the opportunity male house wrens will attract a second female and become polygynous.  Usually this is fairly rare at my study site because of the way the boxes are placed.  This year several males are attempting polygyny, possibly because the population is still rather small.  Usually males attract females on adjacent territories, but bk/wh, gn/al actually has two territories separated by a large field.  You can get a sense of the distance in the picture below.

Bk/wh, gn/al's first territory (A6) is to the right of my car.  His second territory (A3) is against the treeline across the field at the left-most edge of the photo

This year is shaping up to be very successful for bk/wh, gn/al.  He's gone from building a crooked nest in 2011 and attracting zero females to pairing with two simultaneously this year.  Polygyny is great if males can manage it because they can potentially produce twice the offspring.  Polygyny is less great for females.  Males help protect nests from predators and other wrens, help signal when it's safe to leave the nest when the female is incubating, and feed the nestlings with the females.  When the male's attention is split, the females can suffer.  Bk/wh, gn/al's first female is currently half way through her incubation period, so she will be done with her clutch by the time the second female's eggs hatch.  This should decrease the negative effects of polygyny. 

Bk/wh, gn/al's age might have something to do with the fact that he's so successful this year.  Females might prefer older males because they've demonstrated the ability to survive that long and could pass those genes on to their offspring.  Male skills may also improve with age.  Bk/wh, gn/al's nest building skills certainly have!  Perhaps his skills at wooing females have as well.

Tuesday, May 27, 2014

Welcome, Aaron!

I'm very happy to welcome Aaron, my Undergraduate Research Assistant (URA), to the wren project this summer!  Aaron is a Fisheries and Wildlife major from Michigan State University.  Aaron will be helping me complete my experiments this summer, as well as conduct a small project of his own.  He's been here for almost two weeks now and is doing a great job!  This summer he'll be looking at egg coloration in house wrens.  Stay tuned for more news on his project!

Top: Aaron looking excited to be checking boxes
Bottom: Aaron holding the male from A4

Blood Parasites

If aggression helps female house wrens, why aren't all females highly aggressive?  This summer I'm looking for a cost to female aggression that might explain the variation I see in my population.  Last summer I thought that more aggressive females may have less time or energy to raise their offspring.  However, it turns out that aggressive moms actually have bigger, faster growing babies.  This summer I'm investigating whether aggression has an immune cost. 

In males of some bird species, the hormone testosterone that controls male aggression also depresses the immune system.  Males have balance between the reproductive benefits of aggressively defending territories and females and the costs to their overall health.  We don't know yet whether testosterone controls female house wren aggression or whether it negatively impacts health.

To get a measure of health, we are making blood smears to look for avian parasites.  To do this we take a small blood sample from the female's wing (which is very similar to when you get your blood drawn at the hospital).  Then we smear a few drops across a microscope slide.  When the stained slides are viewed under a microscope we should be able to see a variety of parasites in the blood, such as avian malaria.

Preparing a house wren wing for a blood sample

There are many different ways to measure immune function in wild birds, some more complicated than others.  We chose blood slides since they're relatively fast and easy when we're already taking blood sample.  It should also be fun to see the parasites under the microscope!

Slides box with house wren blood smears taken a few weeks ago.  It's more full now!  
Stained slides are in the background and unstained slides are in the foreground

Monday, May 26, 2014

Territory Wars

This summer is off to an interesting start.  The birds arrived a month ag,o but they spent quite a long time at the beginning of nesting before the first female was ready to lay her eggs.  This is possibly because the temperatures have been slightly lower than normal.

Possibly because of this late start, most sections of the field site are in a state of territorial unrest.  Both males and females are involved in these territory fights.  Two days ago we mist netted the male at B5.  After we caught the male, we played female playback to try and get the female.  We caught an intruding male instead!  It will be very interesting to get the genetic results back from the offspring to see whether the territorial male or the intruder fathered the egg she laid the next day.

At C5 two females have been having a week long fight.  The female initially banded there lost her territory for several days to an unbanded female that laid several eggs.  However, on the 4th egg laying day the old female had tossed all the eggs on the ground and reclaimed the territory.  How do we know a wren got the eggs?  Notice the tell-tale beak-sized punctures in the egg below.

Egg found on the ground in front of box C5 with several puncture wounds from a female wren beak.
For one of my experiments this summer, I'm kicking birds off territories to increase the number of floating birds that can challenge territory holders.  I'm hoping to determine whether females that are more aggressive in my tests are able to keep their territories longer.  Although I have only evicted 3 pairs so far, the birds seems to be doing a good job of this themselves.  I might also be getting a helping hand from the resident mammals.  Destruction of the box at B3 by a flying squirrel appears to have set off a chain reaction of territory switches in the B's and C's over the past week.  

   Massive mammal damage to the box at B3

Wednesday, May 7, 2014

The First Females

Several females have now made it back.  There are currently at least 3, but there could be more waiting in the wings.  Only one of these females has previously bred at the field site.  In general, fewer known females return to the field site each year.  In comparison, a larger chunk of males are previously banded and the first males to make it back from migration are general ones that have previously bred at Lux, possibly because they know where they're going.  Of the 11 males that have been identified so far, 9 have bred in previous years.  Offspring that return are also more likely to be males.

In mammals, females are more likely to stay in their natal groups while males are usually the sex that disperses.  Birds show the reverse pattern, with males being more likely to stay in their natal areas and females disperse.  These patterns, known as sex-biased dispersal, serve a useful biological purpose.  If one sex disperses farther than the other, it's less likely that siblings or other close relatives will meet as breeding adults and try to mate.  This reduces inbreeding and it's genetic consequences.  The patterns I've been seeing with the house wrens might be a reflection of this wider behavioral tendency.

First female caught this season at territory A7.  She was actually born at Lux Arbor in 2012 in a different portion of the study site.  She appears to have paired with the male at A7 and sings in response to simulated intruders, despite the fact they haven't started a nest yet.  

The First Nests

This field season is off to a very slow start.  As of yesterday there are now at least 14 males back at the field site, however, many of these males aren't building nests yet despite being around for several days.  The other day I even observed a male courting a female with an empty box!  This doesn't appear to have turned her away- she was still there the next day following her male around and reacting to my presence with agitation. 

Usually nest building begins immediately after males arrive.  The slow start may be due to the weather.  Temperatures have barely made it past 60 this week and morning temperatures have still been in the 30s and 40s.  The next couple days are supposed to be much warmer, so I expect things to take off quickly.

 Nest started at A6 by the first male bk/wh, gn/al who moved across the field.  This nest is now 3 inches tall.

Saturday, April 26, 2014

The First Male

The first bird was back this morning!  The wrens haven't started building nests yet but this morning one male was singing around the A field.  The first males to come back have their pick of territories and they often spend a couple days wandering around before they settle down.

I was only able to see one leg of bands, but based on the colors it's very likely this is the same male who nested in the same area last year.   Bk/wh, gn/al male was first banded as an adult during the summer of 2011 and is featured in my favorite photo of a house wren below.  In 2011 he had a rough time.  He built a lop-sided nest and tried for several months unsuccessfully to attract a female.  In 2012 he returned again and made two nesting attempts, but they were both eaten by predators.  Last year he was the second male to come back from the migration and things went much better.  He had two nests with the same female and raised one to fledging successfully.  He's leading the wave again this year and at least 4 years old he'll likely be one of the older males at the field site this summer.

    Bk/wh, gn/al male from 2011.  It's likely this was the first male I heard singing this morning.

Tuesday, April 22, 2014


Right now is the awkward part of the season where the house wrens have been spotted in Michigan but have not yet shown up at the field site.  Although the wrens are so far silent, other birds are in full swing.  Both chickadees and flying squirrels have claimed some boxes as their own.

A chickadee nest starting at territory 19

A flying squirrel nest at territory 29
 The flying squirrel living at territory 29

Saturday, April 19, 2014

Tracking the Migration

How do you know when the birds are here?  This is a challenging question at the start to every field season.  The house wrens in Michigan spend their winters down in the southern United States and every year they arrive at a slightly different time depending on how the weather has been across the country.  

Here is where citizen scientist efforts are particularly helpful to researchers like me.  Cornell University runs the eBird program ( where birders across world can submit lists of any birds they see.  Checking eBird every days lets me watch the migration in real time.  Citizen scientist efforts like this are extremely useful for ornithologists like myself.  There's no way I could hope to track the migration by myself!  When house wrens are sighted in Michigan, I know they might show up at my field site any day.  Based on the data so far, I expect them to be here by the beginning of next week!

 eBird view of house wrens from March-Apr 19th.  Purple squares show all the places where house wrens have been observed.  The darker the purple, the more times house wrens were seen.

Box Day!

Preparations are in full swing for the arrival of the house wrens!  Boxes went up at Lux Arbor on the 8th in anticipation of their arrival.  Boxes are great homes for house wrens and chickadees but they're also favorites of mice and  flying squirrels.  We take down the boxes each winter to help minimize destruction by these mammals.
A pile of boxes waiting to go out into the field

Box set up at territory C4.  The early part of the season is my favorite since it's so easy to see through the vegetation.  Good for spotting house wren bands!


A male house wren poses for the camera during the summer of 2011

My names is Cara Krieg and I'm a graduate student at Michigan State University in Tom Getty's lab.  This summer I'll be blogging about the research the undergrads in our lab and I will be doing a local population of house wrens.  For more information about my research, check out my professional website at

So why "birds in boxes"?  First, I study house wrens, a small species of song birds that needs to find a tree
hollow or nest box to build their nest.  They're great for research because if you put out boxes, the birds will come to you!  Second,  I hope that my work will help blur the boundaries of the boxes we put around male and female behavior.  In human society we have certain stereotypes about how men and women should behavior.  Men are seen as more competitive, more likely to get into a fist fight in a bar or be into sports, whereas women as seen as more nurturing and maternal, more likely to be focused on relationships and to be nice to your face.  In the scientific world, scientists have similar expectations.  Male animals are a lot more likely to be in fierce fights or to have elaborate ornaments and behaviors to attract the attention of females.  However, as anyone who's paid attention to people knows, reality is a lot more complicated than these boxes.  It turns out nature is a lot more complicated too!  I focus on two traits in female house wrens- female-female aggression and song- that have historically been considered male behaviors.  I'm trying to understand why these female behaviors exist, how they differ from males, and maybe how males and females are more similar than we first thought!