I’m currently studying how Common Nighthawks choose their habitat in northern forests (cliff notes: they like burned forest). I’ve had two field seasons working on that project, and that research is now wrapping up as I finish up my degree. However, I’ve had an exciting opportunity for what’s next come up!
A male Common Nighthawk with a radio transmitter equipped. Photo credit: Alyssa Stulberg
I have been awarded the Queen Elizabeth II Diamond Jubilee Scholarship. It’s a Canadian scholarship that sponsors incoming and outgoing students for up to a year of study in a commonwealth country (check it out here – you might qualify for it too!). Even though I have nearly completed the requirements for my degree, I couldn’t pass up the opportunity to add on another project. Given that I study nightjars right now (a group of nocturnal birds that catch insects in the air), I thought I would continue with that study animal. I had read Dr. Andrew McKechnie’s intriguing work on nightjar physiology (how an organism’s body works) in extreme heat conditions, and was able to meet with him in person at the North American Ornithological Conference 2016. I broached the topic of studying with him, and he agreed the funding had created an exciting opportunity for collaboration. However, he quickly diverted me from my initial nightjar plans and suggested a small bird called a White-browed Sparrow-weaver instead. He forwarded me a few papers on them, and I was hooked.
A pair of White-browed Sparrow-weavers. Photo credit: White-browed Sparrow-weaver (Plocepasser mahali) by Lip Kee licensed under CC-BY-SA 2.0 .
White-browed Sparrow-weavers are a small African songbird. In South Africa, where Dr. McKechnie studies, they can be found in areas that are either semi-arid (kind of dry) or arid (really dry). So the same species of bird is able to live in places that get moderately hot, and in places that get REALLY hot (like 45 degrees C, or 113 degrees F). They’re also abundant and they don’t migrate. As Dr. McKechnie recognized, this makes them a good candidate to study the effects of climate change on songbirds because they are easy to find, to observe, and they spend their life in one location somewhere along a pronounced aridity gradient.
Climate change is the theory (supported by 97% of scientists) that the global climate has been steadily increasing largely due to things humans have done in the last century or so. Basically, we’ve been increasing the amount of carbon dioxide (CO2) in the atmosphere – this is the same gas that you breathe out when you exhale. CO2, along with methane, nitrous oxide, and ozone gases, acts like a blanket, trapping heat from the sun in the atmosphere. Some insulation is a good thing so the earth isn’t a frozen rock, but we’re increasing it past what the earth’s ecosystems have adapted to tolerate, and we’re doing it too quickly for them to catch up to current conditions.
My project will be looking at how the nest insulation of White-browed Sparrow-weavers changes across the aridity gradient I mentioned earlier. Sparrow-weavers are well-adapted to the high temperatures of the environment they occupy, but deserts, despite popular belief, aren’t just hot. They’re also cold at night, especially in winter (in South Africa, that’s June-August). The lack of moisture means there are few plants on the ground and few clouds in the sky, so heat can quickly radiate back into the atmosphere. White-browed Sparrow-weavers live in groups together, so you might expect they would roost together to stay warm at night and conserve energy. But instead, each individual goes to their own enclosed nest each night and sleeps alone. I want to know if birds in drier regions that experience cooler nights have better insulated nests than their counterparts in less dry areas.
White-browed Sparrow-weaver in front of its nest. Photo credit: White-browed Sparrow-weaver (Plocepasser mahali), Northern Tanzania by Nevit Dilmen licensed under CC-BY-SA 3.0.
I’ll be testing this in the field and in the lab. In the field, I’ll use temperature sensors (iButtons) in empty nests, in active nests, and outside in the roost tree. I’ll repeat this at different sites across the aridity gradient. These sensors will record the temperatures and show how each treatment and each site differs. In the lab, I’ll be using collected nests from each site and a 3D-printed model of a Sparrow-weaver. The Sparrow-weaver model will be filled with ~50 degrees C water (to mimic the body temperature of a Sparrow-weaver) and then placed in a temperature chamber that’s set at a typical mid-winter temperature. Based on how quickly the plastic model cools, I can estimate the insulative values of the nests.
It’s important to know how birds in arid environments cope with the temperature extremes. They need to withstand hot days and cold nights. Using enclosed nests appears to be one strategy, and this project will test that prediction. The outcomes of this project will help us better understand how climate change will affect bird populations, and the ecosystems that they are a part of.