By guest author Darren S. Proppe, Phd.
Crash, Boom, Bang! I’ve always enjoyed reading children’s books about construction to my young son. We both appreciate that these sounds are grandiose and represent progress and development on the human front. Admittedly though, another side of me cringes at the glorification of these sounds, and hopes that I can provide my son with a well-rounded understanding of the implications of noise. In the natural world, noise is not always perceived as progress. In fact, it may be downright detrimental in some cases. This seems to be especially true for songbirds. Why? Because songbirds use acoustic signals – better known as bird song – to communicate with other individuals of their species, and even other species. While most of us describe birdsong with terms such as “pretty,” these singing males are working hard to tell other males to stay off their property while inviting that investigating female to come on in. For this system to work, the intended audience must be able to hear and decipher the codes in a male’s song in order to respond properly. Believe it or not, things like how long, loud, or low pitched a song is can actually demonstrate the quality of the singer – preventing physical battles over territories and females.
But human-produced (or anthropogenic) noise gets in the way of all of this. Research shows that females are less likely to respond to a paired male if they can’t hear his song. In addition, males whose songs are not perceived correctly may be less able to keep out those intruders. But there is more; anthropogenic noise results in higher stress levels in some birds, which can lead to lower immunity and ultimately may reduce longevity and reproductive fitness. It also forces birds to use their visual senses more often, likely because they cannot hear threatening sounds in their environment. When you’re on a limited time budget, looking around more means less time searching for food. This can be problematic since songbirds generally store just enough fat to get through each night. As a result of these processes, biologists now know that areas with high levels of anthropogenic noise have fewer songbird species, fewer individuals, and sometimes less healthy bird populations.
One might realistically respond by reminding us that noise is not new. In fact, things like rain, waterfalls, wind, etc., have been around for a long time. So why is our noise so problematic? Well, the sound signature is different. Anthropogenic noise is more regular and tends to be low in frequency. These sounds, including things like vehicle and airplane noise as well as industrial sounds, overlap the frequencies used by many bird species, creating the `masking’ effect that disrupts communication. Notably, some species with vocalizations that are higher than the frequency of anthropogenic noises are less likely to avoid noisy areas. Some birds even shift their song frequencies upward in noisy environments, suggesting that behavioral adaptation is possible in some species.
So what can we do? We know that habitat loss and fragmentation are driving some pretty solid declines in many songbirds. This is especially apparent in the endangered Kirtland’s warbler. Fortunately, careful land management for this, and other, species has had some positive impacts. But, preserving good habitat next to a road, or a gas compressor, may not be enough. We need to continue to build our understanding of how noise affects songbird species. As results come in, we may need to consider noise regulation as a vital aspect of conservation management. Maintaining a natural soundscape may be an important and often overlooked component of habitat selection in songbirds. In the case of the Kirtland’s warbler, initiatives are underway to understand more clearly how this valuable species responds to noise. Fortunately, management agencies have already placed regulations on how close noise-producing sources can be to Kirtland’s habitat. But species-specific data may allow them to objectively prioritize noise regulation among the myriad of other variables that impact the persistence of the Kirtland’s warbler, such as cowbird control and the protection of winter habitat. In the end, we may not completely stop the Crash, Boom, Bang of human development – and I’m not sure that is a good overarching objective. But pinpointing where and how we can minimize noise might keep our songbirds a little happier and a little healthier. Truth be told, it might do the same for us too.
Learn more about the study and check out Darren’s video here.
Darren Proppe is an Assistant Professor of Biology at Calvin College in Grand Rapids, MI. Darren is working with Kirtland’s Warbler conservation partners to understand how noise potentially impacts the nesting activities of the Kirtland’s Warbler. Research projects like the one he discusses here are important for understanding how conservation programs can develop in the future to ensure the population of the species continues to thrive. Having diverse partnerships with academic institutions provides important connections to the community and unique funding opportunities for conservation work.