In an earlier article, we had looked at the process of birds building their nests – with the specific example of two Northern Mockingbirds over the 2021 Winter-Spring. But as I have found time and again, nothing is ever the same for all birds – and the same applies to nests! Every group of bird species has their own way of building nests. But just why is that?
This summer, I was biking near a school in my neighborhood, and I happened to notice a large number of curved-winged birds circling around a large grass field on the playground. A closer look, and a glance at the iridescent blue wings and orange undersides, showed me that they were Barn Swallows. I often see swallows flying around near-coastal areas and open grassy spaces, so it wasn’t that strange of a sight. However, I decided to look around and see if I could find any of them perching.
After about five minutes, I found that most of the adults were repeatedly flying under the school’s rafters. Looking under there, I found an amazing sight – a full colony of swallow nests, with parents roosting on some, and fledglings poking up their heads!
Two adult Barn Swallows roost over their mud nest (Fremont, CA, August 2020) 
Juvenile Barn Swallow perched among the rafters
(Fremont, CA, August 2020)
What I noticed, though, was that these nests were unlike the stereotypical “nest” image, the one often associated with songbirds. I recently posted an article where I talked about the shape of a Northern Mockingbird’s nest, which is primarily built with twigs. However, take a closer look at the swallows’ nests.
These nests are typically constructed with much looser materials – a mud basing, and tools such as grass or rocks to provide structure. As the image shows, this nest is built out of mud! And swallows aren’t the only birds who build their nests this way! Black Phoebes, for example, often use mud for their nests as well! Similarly to many swallows, they are often found nesting in building rafters.
Female Black Phoebe (Fremont, CA, July 2021) 
Black Phoebe Nest
(Citation: http://www.arizonensis.org/)
The variety doesn’t stop here – for example, birds like Gyrfalcons often build their nests on rocky cliff ledges. Orioles often create hanging, hammock-like nests which protect them from predators. Horned Larks often create nests on the ground.
So why do birds take on these different strategies when building their nests? A lot comes down to other characteristics of each bird. After all, the range of different species – from songbirds to raptors to waterfowl – causes variety in everything from diet to habitat to body size. And all of these end up influencing the way the bird nests.
For example, Horned Larks, as I mentioned earlier, typically nest on the ground. Although the exact reason why is not known, their habitat, diet and behavior sheds some light on this. As a species that typically lives in open areas like plains or mountains, it is often found foraging for insects and seeds along the ground. As a result, they typically do not need to fly high, and so it makes more sense to nest along the ground.
Likewise, orioles are commonly found flying around trees, and very rarely along the ground. Additionally, they have plenty of predators, and are easy targets due to their bright coloring. As a result, their nests need to be doubly secure, and so they often build them high up in trees, constructed as tightly-wound hammocks that are hard to attack.
Every species of bird is different, and so too is its nest. And as we have seen, all of its characteristics come into play when a bird has to decide on its nest. Next time you see a nest and wonder “which bird built this?”, think a little bit about your surroundings – are you in a forest? Near the ocean? In an open plain? What sort of birds would live here? What sort of food would be common for them? With this mindset, seeing a nest becomes more than an identification game – it becomes a journey into the bird’s entire mindset.
Sources