Birds become night owls with light pollution - Expert Reaction

Birds around the world are singing for nearly an hour longer on average due to light pollution, a global study finds.

Millions of birdsong recordings including some from NZ’s North Island were used in the study, just published in the journal Science. The researchers found that light pollution had a greater impact on birds with bigger eyes and those with open nests, as well as migratory birds and those with larger geographical ranges. Such birds were more likely to sing later into the evenings and earlier in the mornings as a result of light pollution.

The Science Media Centre asked experts to comment.

Dr Bridgette Farnworth, Lecturer, School of Biological Sciences, Victoria University of Wellington, comments:

“Artificial light at night is spreading rapidly across the globe. While it has transformed how we live after dark, it also disrupts wildlife in surprising ways. This new study by Pease and Gilbert shows that birds in brighter environments sing for nearly an hour longer than those in darker landscapes.

“Back home in New Zealand, similar effects of light pollution are emerging for our birds. Tūī start singing later under LED streetlights, kiwi avoid illuminated areas, threatened banded dotterels are killed by predators using streetlighting to hunt, and Cook’s petrels are dying from internal injuries caused by crashing after being disorientated by light at night.

“These changes may seem small, but they carry real consequences. Pease and Gilbert do a great job considering how birds in their study might be affected and suggest that extra time spent singing could mean less time resting; a big challenge during the breeding season, when birds must sing to attract mates and raise chicks at the same time.

“For New Zealand, we need to consider what any changes in behaviour mean for birds and other wildlife. The good news is that the solutions can be simple: before switching on a light, ask if it’s really needed. A small act that makes a big difference for the species that prefer life in the shadows.”

Conflict of interest statement: No conflicts. “Currently funded by Rutherford Fellowship to examine ecological impacts of light pollution.”

Dr Natalie Forsdick, President of Birds New Zealand, comments:

“We are seeing increasing light pollution, not just in urban centres, but across the whole country, which is likely to have impacts on our birdlife like this study demonstrates. Light pollution may disrupt the natural daily patterns of birds in ways we don’t yet know about, and there may be different impacts on native species like tūī compared with introduced birds like mynas. Experimental studies in New Zealand have shown a range of outcomes, from no effect, to increased night-time predation by black-backed gulls on threatened species like banded dotterels.

“One of the biggest concerns in New Zealand as the seabird capital of the world is impacts of light pollution on seabirds, where urban light pollution may be mistaken for moonlight by juvenile birds, attracting and disorientating species like Cook’s petrel or Hutton’s shearwaters. This can result in fall out, where birds crash land or collide with buildings, and may become injured or grounded.

“Reducing light pollution through limiting use of unnecessary artificial lighting, or converting to lighting types that have lower emittance can reduce the impacts on these seabirds, and other fauna.”

No conflict of interest.

Associate Professor Kristal Cain, Te Kura Mātauranga Koiora | School of Biological Sciences, Waipapa Taumata Rau | University of Auckland, comments:

“In recent years there has been a tremendous amount of interest and concern about how the amount of light humans are pumping out is affecting the world around us. The problem has been that it is difficult to do the really big studies that are needed to understand which animal are getting affected the most, and why.

“This paper using the bird song data collected by thousands of volunteers and measured when birds start singing in the morning and when they stop for the night. They found that in brighter areas – birds start singing early and keep going later into the night than in dark areas. Importantly, most of the bird song was collected in North America and Europe. We still need to do similar work in the rest of the world to see how widespread these patterns really are. The manu of Aotearoa are quite unique in many ways. Even more importantly, we need to know how this affects the birds’ survival and reproduction.

“Some evidence says too much light stresses birds out and makes them more vulnerable to infection and disease – but the lack of sleep might also mean they have more or healthier babies. Importantly, all this artificial light is not good for us either. So, it’s good for everyone to limit light at night to only when it is necessary. There are lots of little things we can do as individuals and as communities to reduce the amount of light that animals experience at night. For example, closing your curtains can do wonders, make sure the lights are only on when needed, and are no brighter than needed. Communities can put shields on streetlights, so they don’t spill light everywhere, use warmer light colours, and plant trees to contain some of the light. Check out this webpage for information on more steps to take.”

Conflict of interest statement: “No conflict – but also have done research on light at night.”

Prof Stephen Marsland, AviaNZ project leader; and Professor of Mathematics at Victoria University of Wellington, comments:

“Bird vocalisations have much to tell us, even if we can’t understand exactly what they are actually singing about. In this study the power of large-scale data collection and automated analysis has shown that – at least in the global north – the effects of light pollution are significant across many species and habitats. Birds exposed to more artificial light at night are starting to sing earlier and putting in longer shifts.

“Does this study have relevance here in Aotearoa New Zealand, with our relatively low population density and unique taonga species? While we would need more data to be collected and analysed to be sure, the answer is very likely yes: their analysis shows that migratory species, of which we have significant numbers, showed stronger effects, as did species with larger eyes, which may be correlated with specialising in low light, being either crepuscular (active at twilight) or living in dense habitats.

“For our taonga species, two particularly important questions remain: does the day birds putting in longer days mean that our nocturnal species are sleeping in, especially as they come closer to our cities, through efforts like Capital Kiwi? And are similar effects seen for the seabirds that we have in such amazing numbers? It is questions like these that the interdisciplinary AviaNZ project seeks to answer as we make sure that the voices of New Zealand’s birds are heard.”

Conflict of interest statement: “No conflict of interest, but am carrying out research on bioacoustics.”

Dr Rachael Shaw, Senior Lecturer in Behavioural Ecology, Victoria University of Wellington, comments:

“In Aotearoa, we know that light pollution from fishing vessels and cities negatively impacts seabirds, causing injuries and fatalities when birds use these artificial light sources for navigation. This new study suggests that light pollution is in fact altering bird behaviour at a global scale, by keeping birds active for longer periods each day.

“This could mean that native birds living near well-lit towns and cities in New Zealand are starting their days earlier and getting to sleep later than their rural counterparts. These possible impacts warrant further attention and add to our growing list of concerns about the impacts of light pollution on wildlife.”