In July, while workers were wrapping up construction of the new University of Arizona Environment and Natural Resources Building, or ENR2, they discovered someone else wrapping up a little construction of her own. That someone was a hummingbird, and she had built her nest on a data cable dangling directly in front of a security camera.
A live feed was quickly launched on the UA's Planning, Design and Construction website. In the weeks that followed, the world watched as twins were hatched, mouths were fed and wings were tested. Media outlets picked up on the story. Last week, the fledglings took to the sky. Staff believe the birds are either an Anna's or black-chinned hummingbird.
In light of hummingbirds’ prevalence here, William Mannan, a UA professor of wildlife ecology, answered a few questions about the tiny birds, their beefier avian cousins and Tucson’s diverse urban wildlife.
Q: How do hummingbirds choose where to build a nest?
A: They pick places where there’s a support system. Almost everyone has hummingbirds nesting in their mesquite tree or pine tree. The site is often just a little, teeny branch that hangs down, and it supports that tiny cup nest they make.
Q: When it comes to building a nest, how do birds adapt to urban environments?
A: Birds that live in urban environments are not what you would call adapted to urban environments. They’re doing what they normally do. It’s just that urban environments provide the resources and the conditions that they recognize as nest sites. In general, and I would say this is true for most birds, their urban environments can be very rich. For example, they can offer lots of food and lots of shelter.
Q: How do hummingbirds fare in Tucson?
A: I don’t believe the adults are often killed by predators. My sense is they’re too little and too quick. For example, the species I work with, Cooper’s hawks, don’t pay any attention to hummingbirds. The hummingbirds are too little, and the hawks couldn’t catch them anyway. Also, there is a lot of food for hummingbirds here, feeders and flowering plants. Obviously there’s plenty of water relative to the desert, and there are places to nest. A place to nest could be anything that matches their perception of what a nest site is. In ENR2, a little wire hanging down that was stable triggered something that said, "This is a good place to build a nest."
Q: How do other birds fare here?
A: Electrocution, being hit by cars and flying into windows are major sources of mortality for urban birds. Tucson Electric Power has done a really good job of reducing the number of large birds that are electrocuted. I work with TEP on that. Poisoning also is a potential problem, if people use poison to get rid of pack rats or other pests. The bottom line is that urban areas can be positive and negative for species that live here.
Q: What should people consider when they come across a nest or a fledging?
A: Most birds need to be left alone. If you bother some birds during incubation, before their eggs are hatched, the adults may abandon the nest. That often happens to quail that nest in town especially if they put their nest right by an entrance to a building, and people have to go in and out. If you flush a bird out enough times, it will abandon its nest. The admonition we give people is to just leave them alone as best as you can.
One of the issues we have with the hawks we study is that the fledglings end up on the ground pretty regularly for a day or so, and that’s when people "rescue" them because they think they’re orphans even though mom and dad are sitting right overhead taking care of them. So, we’ve really tried to educate people not to pick them up. It has nothing to do with the smell of humans. That’s a myth. Instead, it has to do with this: If you take them to a rehabilitation center, the fledglings are not going to go through a critical developmental period that they need to go through to learn to fly and hunt.
Q: One last question: There seem to be a lot of hummingbirds in Tucson. Is that correct?
A: There are a lot of hummingbirds in this part of the world. Ramsey Canyon is a mecca for birders to go to look at hummingbirds. The Southwest United States and Arizona, in particular, are places where birders from all over the world come. We live in a very rich place from the standpoint of urban animals. People have varying opinions about some of them, coyotes, raptors, bobcats and the mountain lions that live outside of town. But really, we live in a fascinating place from an urban wildlife standpoint, so I think this is a pretty special place to live.