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).