I am using the incredible diversity of mechanisms that produce animal coloration to understand the evolution of signal production. Through a multi-university collaboration, I was able to help uncover how carotenoid-based coloration (e.g. typically the reds and yellows in birds) evolved through an ordered evolutionary pathway of carotenoid modification and deposition into bird feathers in Fringillid finches (Ligon, Simpson, et al. 2015). Now, I am using scanning and transmission electron microscopy to measure the surface and internal structures of hummingbird feathers and test how these feather structures vary among species, predict variation in feather color, and possibly co-evolved with courtship behaviors.
My other research themes:
1. Sensory and evolutionary ecology of animal signals and their diversity
2. Mechanisms and evolution of signal interactions
While communicating animals can use multiple signals simultaneously and these signals can interact during use. For example, during hummingbird courtship a male’s iridescent throat plumage is oriented and positioned towards females and the sun in specific ways through their courtship dances. The color-behavior-environment interactions shape the appearance of a male’s colorful plumage to the female, a unique signal property created by the signal interactions. Using six North American hummingbird species as my study system, my research in this theme focuses on understanding the mechanics of these signal interactions, how signal interactions vary among species, and how signal interactions co-evolved with the interacting signals themselves.
Through a novel display re-creation method, I developed, where I mapped the orientation-and-positional movements of video-recorded hummingbird courtship dances combined with full-spectrum photography, I quantified male color appearance, thus directly measuring properties of signal interactions. I discovered that male color appearance is not solely tied to the color of his ornaments (i.e. brighter feathers does not mean brighter appearance), due to behavioral alterations of appearance (Simpson & McGraw 2018), which demonstrates the need to break with traditional, static-snapshot color measurements and instead study animal coloration as a dynamic trait or behavior. Among species, I found that color appearance evolved through two divergent evolutionary pathways alongside exaggeration in plumage or behavioral displays (Simpson & McGraw 2019).
I am continuing my work on signal interactions by evaluating signal interactions in spiders, peafowl, and Peruvian hummingbird species.
My other research themes:
1. Sensory and evolutionary ecology of animal signals and their diversity
2. Evolution of signal production mechanisms
I am studying how an animal’s ecology and signaling environment shape the evolution and diversity of signals. The bulk of my work in this theme has focused on color evolution in Paruild warblers. Warblers vary considerably in color among species, occur throughout a wide variety of habitats, ranging from pine forests to swamps to meadows, and differ in several ecological traits, such as migratory behavior and species overlap. I previously found that evolutionary changes in migratory distance were driving losses of female coloration in this group, contrary to previous theory on how sexual color differences were primarily driven by changes in male coloration (Simpson et al. 2015). I am currently studying how natural and sexual selection together drive color diversity by each acting on different aspects of color and continuing to explore other factors driving warbler color evolution.
Additionally, in collaboration with the Smithsonian Tropical Research Institute, I studied a neotropical songbird, the red-throated ant-tanager (Habia fuscicauda) in Panama and found spatial variation in ambient light and noise predicted variation in male color and song (Simpson & McGraw 2018).
I am excited to announce that my wife and I just completed our move to Canada to start our new post-docs this week! I will be working with Stephanie Doucet at the University of Windsor. I will be continuing to study the evolution of coloration in birds, but in collaboration with Stephanie and her husband, Dan Mennill, I will also be studying the co-evolution of color and song. This is particularly exciting for me as I am interested in studying multiple signals and while hummingbirds and many other birds/animals communicate using elaborate dances and ornate color patches, they also signal in other modalities like acoustic or odor signals. Additionally, I will continue to study the mechanisms of color production in hummingbirds using electron microscopy. I will be looking at the surface and internal structures of hummingbird feathers to understand how these structures co-evolved with their feather reflectance, color appearance during displays, and courtship dances.
In the meantime, my recent publication from my dissertation in Ecology Letters picked up some popular press! I was interviewed by a writer from Science for their news section, and they both wrote an article about my paper and created a really neat video! Be sure to check them out!
With everything that has been going on (defense, moving, etc.), I realize that I have fallen way behind with my blogging! So here is the final update from my Peru field trip, I hope you enjoy!
For the last leg of my Peru trip, I journeyed to Southern Peru, specifically to the area around Arequipa, which was a Spanish colonial city nested in a valley around several volcanoes. Here I had pretty good success working with two of my target hummingbird species – Peruvian sheartail (video of display, side video) and oasis hummingbird (video of display, side video).
I stayed at a wonderful hotel outside of the city, which was great because I could walk to one of my field sites that was just outside of town. At this field site, along many farm plots, wound a creek along some desert hills. It was among these hills and the creek bed where I found both species holding territories and displaying.
My other field site was about 2 hours away from town, along another riverbed, but in a much more desert-based habitat, as you can see from these pictures.
At this field site, I was looking for the elusive purple-collared woodstar, and while I never was able to work with them, I found some additional oasis hummingbirds. The best part about this field site, is that I caught an oasis hummingbird male with my bare hand!! It was hanging out near the female in her cage, as in the blow photos, and I just quickly pinned it against the cage and was able to capture it. (it was not hurt in any way!) So that was an awesome moment for me in my research.
Overall, I loved the area around Arequipa. It was a beautiful place, surrounded by these snow-capped volcanoes, and the people were very friendly. I had a great time working with my wonderful field assistant, Carla Llerena Quiroz, and visiting the university/museum of my collaborator, Mauricio Ugarte at El Museo de Historia Natural de la Universidad Nacional San Augustin, where I gave a seminar for them. All in all, this leg of my trip was very successful, and I then returned to the US to begin analyzing those data I collected and wrapping up my dissertation. More on all that in the future, so for now, here are a few additional photos from highlights of my Arequipa trip:
Well its finally time! I am defending my Ph.D. this Friday at 2:00 PM (Arizona time). All are welcome to attend my talk, which will be about 1 hour, and is on Arizona State University’s Tempe campus in Life Sciences E-wing 244 (LSE 244).
My talk will cover my four dissertation chapters on the evolution of hummingbird coloration and courtship displays. I will probably write a summary blog of my dissertation later this summer, but if you want to see the presentation in person, please stop by!
Wish me luck!
Well, I’m back from Peru and busily trying to wrap up my dissertation. While I will definitely write a final Peru blog post in the near future, I also recently wrote a guest blog post for Oxford University Press blog about my first dissertation chapter titled, “How do male hummingbird dance moves alter their appearance?” published in Behavioral Ecology. This chapter is titled “Two ways to display: male hummingbirds show different color-display tactics based on sun orientation,” and tests how broad-tailed hummingbirds orient towards the sun as they dance and how their sun orientation alters what they look like. I hope you enjoy the post and paper, and please let me know if you have any questions about the study!
Also check out this .gif they made for me from one of my YouTube videos.
While doing my fieldwork in Peru, I took a short trip to Cusco to visit Machu Picchu, and the other surrounding Inca ruins/temples, with my sister who visited me from Connecticut! For those who do not know, Machu Picchu is probably the largest tourist attraction in South America, and for good reason – it was spectacular. The Incas were one of the many native peoples that lived in Peru, and they formed a giant empire in the Andes Mountains between 1438 and 1572. The current city of Cusco, was at the heart of this empire, and a very important site for the Incas, spiritually and logistically.
The Incas also built many temples and complexes near Cusco, with the most famous being Machu Picchu, which was never discovered by the Spanish Conquistadors. While the Inca empire was vast and had achieved many technological innovations, especially with agriculture, architecture, and astronomy, the Spanish Conquistadors unfortunately brutally conquered the Incas and many of their discoveries have been lost. Luckily, modern science has been a great help in uncovering the secrets of Machu Picchu and other Inca sites.
During our travels around Cusco, we first visited a place called the Sacred Valley – it is the valley between Cusco and Machu Picchu. Along this valley are many interesting ruins, several churches that the Spanish built on top of Inca temples, and groups of people who still carry out many of the Inca traditions, and I was able to visit many of these places. We first visited the town of Chinchero where we saw one of the Spanish churches that was built on top of an Inca temple.
We were also able to watch how people weave alpaca fur together and use many different natural ingredients to dye woven materials into many different colors.
Then, we visited the town of Pisac and went to the Inca complex found there. At this complex, we learned how the Incas built their temples with specific designs that incorporated the movement of the sun and the moon. The Incas were brilliant astronomers and used their knowledge of the sun, moon, and stars to understand seasonal and weather patterns to help their agriculture. Here are a few pictures of the complex at Pisac:
After Pisac, we visited to the town of Ollantaytambo, at which is located the famous Temple of the Sun. This temple is particularly interesting because of the amazing architecture and engineering abilities of the Incas. If you look at these pictures, you can see how they managed to fit different giant stones together, without mortar, almost perfectly.
From Ollantaytambo we took a train to Aguas Calientes to spend the night, before heading up to Machu Picchu. Our visit to Machu Picchu was awe-inspiring. In the morning it was very cloudy and misty, giving it a mystical feeling, and by mid-day the sun came out, which gave us a great view of the entire complex. Here were learned about the significance of the complex and how it was laid out, with brilliant city planning and lots of terraces for agriculture to feed the people.
After our tour of Machu Picchu, we took the train back to Ollantaytambo, and then a car back to Cusco. The next day, we visited various ruins around Cusco, including the famous temple Saqsaywaman. We learned about the specific meanings of all the different ruins, and how the Incas used water channels and natural springs to spread water throughout the Cusco area, similar to how they did in Machu Picchu too.
Finally, we visited many of the museums in Cusco, which were very informative and a great follow up to our tours of the Inca ruins and Machu Picchu. Unfortunately, we were not allowed to take photographs in these museums, so I cannot show much from them.
We were fortunate enough to visit these places in the low season, so there were much fewer people, which I would recommend. The high season is between May and October (I believe) and there are huge, huge crowds during that time. Overall, I would highly recommend everyone to visit Cusco, the Sacred Valley, and Machu Picchu. It definitely lives up to the hype, and I thought exceeded it.
Finally, given that this post was mostly an overview of my visit, if you are interested in learning more about a specific place/ruin/topic please let me know!
That’s right, I am back in Peru right now studying hummingbirds. I know, it is a bit crazy for me to be gathering data the semester I plan to graduate, but I got a grant to travel to Peru, and I am not about to say no to that!
Anyways, this trip to Peru is much more structured than last time. Last time, I was scouting the country and searching for field sites. Now that I have field sites, I am staying those places for longer periods of time. Right now, I am in Northern Peru three weeks. I am currently staying at the Center for the Spectacled Bear Conservation Society (SBC), in a small town called Batangrande. It is a family run field station that is near the Andes Mountains and in the tropical dry forests unique to this region (called Tumbes). It is also a great location to study two species of hummingbirds: short-tailed woodstar (Myrmia micrura) and purple-collared woodstar (Myrtis fanny).
So far, things are going well. I have found territories of multiple males for both species, including over 10 territories for the short-tailed woodstar. Now I am working to trap a female of each species and use her to film the courtship dances of the males.
The short-tailed woodstar, which is a species somewhat endemic to the Tumbes region, is a tiny hummingbird with a ridiculously small tail (that is actually what it says in the bird guide book). The males have an iridescent purple gorget (throat patch) and sing a song similar to the Costa’s hummingbirds in the US. They live in the tropical dry forests here, which are a very interesting habitat. It is very hot and sunny here, but the habitat is different than many I have visited in Peru. Here are some pictures of the dry forests:
The purple-collared woodstar, is much more widespread in Peru, but tends to live at higher elevations. For them, we drive up into the Andes until about 6,500 ft (2,000 meters), and work in the montane scrub and agriculture areas there. I like these sites because they are much cooler than the dry forest below, and the mountains are very beautiful. This species has been a bit weird for me, because we have found many, many females, but only a few males. But the males we found will work just fine, and I have already seen them display naturally to females, which is a great sign! The purple-collared woodstar is especially interesting to me because of the color of its gorget. Most of the species in the group of hummingbirds I study (the bee hummingbirds) have purple, pink, or red gorgets, but the purple-collared woodstar has a greenish-blue iridescent gorget. I do not have any great pictures of the males yet, but here is the habitat in which we have found them, and a photo of the male from the side:
That is all I have for now, but I should have videos of courtship displays and photos of males that I have captured soon!
For this post, I am going to take a break from posting about my Peru travels to talk about hummingbirds and why they are so cool. My Ph.D. is focused on understanding hummingbird coloration and their courtship displays, but I am always asked why I chose to study hummingbirds over other animals. It certainly was not because they are an easy group to study. Quite the opposite – they can be very difficult to work with in some ways. Throughout this post, I am going to elaborate more on why I chose to study hummingbirds, but also in general, why hummingbirds are so interesting and fun to study. I am also going to include lots of pictures of different hummingbird species, as these are such photogenic animals!
Hummingbirds are only found in the New World (North, Central, and South America). There have been hummingbird-like fossils found in the Old World, and it is suggested that the ancestors of hummingbirds moved from the Old World to the New World through the Bering Straight. The ancestors then theoretically made their way down to South America and hummingbirds evolved from there. Hummingbirds are thought to have evolved about 22 million years ago, based on fossil and genetic data. Some of the oldest hummingbird species are pictures below.
There are roughly 340 species of hummingbirds currently, though new species are still being discovered. While we boast around 20-25 species in the United States, hummingbirds are most diverse in the Andes Mountains and Amazon Rainforest. The country with the most hummingbird species is Colombia, which boasts over 160 species!
Hummingbirds span a wide range of body sizes, with the smallest hummingbird (bee hummingbird) averaging around 2 grams (0.07 oz) and the largest hummingbird (giant hummingbird) averaging around 20 grams (0.7 oz). Many hummingbirds range between 3-7 grams overall (0.11-0.25 oz), and most of the species I study range between 2.5-4 grams (0.09-0.14 oz).
Hummingbird flight is also very unique relative to birds. They flap their wings in a figure eight pattern, and unlike many birds, they generate similar forces with their upstrokes compared to their downstrokes. Hummingbirds can also hover, a rare trait in birds, and I believe they are the only birds that can fly backwards. Their metabolism is also very fast. Their weight can change quite a bit over the course of a day as they eat and burn up energy. And hummingbirds hearts can beat over 1000 times per minute. This fast metabolism poses a problem at night, when hummingbirds have to go many hours without eating. Some hummingbirds will go into a hibernation-like state at night, called torpor, to conserve energy. They essentially shut off their bodies, and their heart rate can drop from 1000 beats/min to 100 beats/min. This is especially common in hummingbirds that live in colder places or at high elevations. Some hummingbird species like the Ecuadorian Hillstar can occur up to 17,000 feet (~5200 meters) above sea level!
One misconception about hummingbirds is that they only feed on nectar. While they have definitely evolved many specializations for nectar feeding, such as their hovering, long bills, and fast metabolism, they cannot survive on sugar water alone. Hummingbirds feed on insects, such as fruit flies, in order to obtain essential proteins, vitamins, and minerals. However, hummingbird bills can present interesting challenges to eating insects, such as for the sword-billed hummingbird (longest bill to body length of a bird) or the sickle-billed hummingbird (below). Also, hummingbirds interestingly have forked tongues.
Because many hummingbirds live in the tropics, most do not migrate. There are some high elevation hummingbirds that will migrate to lower elevations during the winter/dry season in the tropics. In North America, we have several species that migrate. Some rufous hummingbirds travel from Mexico all the way to Alaska and back every year. Some ruby-throated hummingbirds fly straight across the Gulf of Mexico, an incredible feat for a bird that cannot store too much fat for the long trip. Interestingly, some hummingbird migratory paths have been changing due to hummingbird feeders. Many rufous hummingbirds are now found migrating to the Southeastern US instead of Mexico. Other species have expanded their ranges due to humans. Anna’s hummingbirds have expanded their range into Canada and Arizona, when they originally occurred in California.
There are several reasons I decided to study hummingbirds. The first reason is their crazy colors. You can essentially find every color under the rainbow in hummingbirds, and some species actually do seemingly have every color themselves (like the fiery-throated hummingbird). Hummingbirds also possess a fascinating type of color called iridescence. This type of color looks different depending on the angles it is observed from and the angles it is illuminated from. Essentially, as the hummingbird moves around, the color of its plumage will change, as shown in this video (link). Because I am interested in how behaviors and colors interact and co-evolved, iridescent coloration provides a great system to study these interactions. Overall, the species I study, while very pretty, are actually quite boring relative to many other hummingbird species. Here are a few of my favorite species:
Another reason I study hummingbirds, is that many of them have elaborate dances males perform to females. This is especially true in the 10- species I study. And the interesting part is that the species I study all have similar variations of two types of displays: 1) the dive display ; 2) the shuttle display (link). The dive display is typically where a male flies high into the air, and then dives down over or near his target. The shuttle display is where a male flies rapidly back and forth in front of their target (usually a female), facing it and presenting their throat coloration. Because these displays are similar across species, I can really explore how evolution shaped each species’ specific display and why they are different from each other.
Hummingbirds are also very charismatic and fun animals to work with and observe. They are so bold and curious. They live such fast-paced lives and are always interacting – mostly fighting. And because they occur all over the place, I have gotten to travel all across Arizona, California, and now Peru. Hummingbird’s reliance on nectar can also make it easy to lure them to feeders, where I can observe and catch them. It is still quite difficult to catch a hummingbird sometimes, but feeders definitely help. Overall, hummingbirds are such unique and interesting animals, providing lots of opportunities to study many aspects of their biology. But hummingbirds also provide opportunities to ask broad questions about color and behavior evolution, which is the key reason I am studying them. I actually just submitted my first chapter to a journal, so when that ultimately gets accepted (fingers crossed!) I will blog about those results. For now, I hope this post taught you a few cool facts about hummingbirds and provided a better explanation for why I study them. If you are interested in learning more about hummingbirds, there are two hummingbird-focused PBS Nature documentaries I would recommend. The first is Magic in the Air and the second is one I helped with called Super Hummingbirds (available for free here).