Artificial light at night

In many places, dark skies at night are a thing of the past. Night-time cityscapes can be beautiful, but they are not so good for wildlife and sometimes not for us either. Like most of MCB's research projects, those projects studying the effects of ALAN draw from multiple MCB research priorities.

One such project investigated how ALAN affects immunity in relation to the intensity of a parasitic infection in a songbird. Another is assessing the impact of ALAN (artificial light at night) on avian reproductive schedules.

Researchers: Ellen Ketterson, Sarah Wanamaker, Malaak Alqaisi, Ariel Tysver, Samantha Diedrich, David Sinkiewicz

Artificial light at night (ALAN) is common in urban environments, and chronic exposure has been shown to influence immunity in wildlife, perhaps increasing the risk of infections. Few studies, however, have addresses ALAN’s effect on immunity in migratory birds.

Researchers at MCB experimentally tested how ALAN affects immunity at the cellular level in relation to the intensity of a parasitic infection in a songbird, the Dark-eyed Junco.

The project

To better understand the effects of artificial light on birds, Indiana University researchers with the Ketterson Lab captured two subspecies of dark-eyed juncos, one migratory and one non-migratory, that share wintering grounds in Virginia. They transported the birds to Kent Farm Research Station in Bloomington, Ind. and subjected them to different light regimes in a lab setting.

In one experiment, the research team subjected the birds to a light regime that mimicked what they would experience in the wild. Some of the birds, however, were exposed to low levels of white light during periods that would normally be marked by the pitch black of night. Researchers observed that the latter regime contributed to the reactivation of dormant infections, such as malaria. The finding potentially has implications for public health as birds serve as a reservoir for human diseases, such as Lyme disease and West Nile virus.

During the study period, the researchers measured the male birds’ reproductive organs, which enlarge during the breeding season, to determine when the birds were starting and ending their breeding cycle. On average, birds subjected to artificial light at night started their reproductive cycle approximately two weeks earlier than birds subjected to darkness, a response that risks placing birds out of step with their environment and threatening breeding success.

The path forward

To further understand the effects of artificial light at night on birds and how to reduce negative impacts, the researchers are conducting a follow-up study to measure impact of ALAN on stress, immune function, and parasite load. The team is also attaching chips to the birds that measure birds’ nighttime activity levels and time of migratory departure to see if migration is also affected by artificial light at night.

Featured media

• ERI Study: Artificial light at night changes seasonal responses in birds
• Artificial light at night wakes up dormant infections in birds

Publications

• Exposure to artificial light at night accelerates but does not override latitude-dependent seasonal reproductive response in a North American songbird
• Artificial light at night amplifies seasonal relapse of haemosporidian parasites in a widespread songbird

Researchers: Devraj Singh, Jesse Montoure, Ellen Ketterson

In the modern era of industrialization, illuminated nights have become a defining feature of human-occupied environments, particularly cities. Artificial light at night (ALAN) has been shown to have negative impacts on species living in the wild.

To test whether ALAN affects reproductive timing of bird populations that winter in the United States but differ in when and where they breed because some migrate and some do not, MCBB researchers compared physiology in resident and migrant Dark-eyed Juncos (a songbird commonly known as the snowbird) that were exposed to ALAN.

As expected, residents prepared to breed earlier than migrants because migrants migrate before they breed. ALAN accelerated reproductive development in both migrants and residents—though the difference between them (residents ready before migrants) was maintained despite exposure to ALAN. The timing difference may have a genetic basis, but the timing itself was flexible in response to ALAN. As the climate warms, it’s possible that earlier reproduction will be favored and the effects of light at night may not all be negative.

Learn more about the study