For this week’s roundup, there are two new papers that used data from Breeding Bird Atlas programs in order to spot trends in bird populations in relation to environmental changes.
One study with Atlas data took place in the Catalonia region of Spain and also involved data from a citizen science project called the Common Bird Survey (bird counts along transect routes),
Herrando, S, M Anton, F Sarda-Palomera, G Bota, RD Gregory, and L Brontons. 2014. Indicators of the impact of land use changes using large-scale bird surveys: Land abandonment in a Mediterranean region. Ecological Indicators 45:235-244.
Another study with Atlas data took place in South Africa and also involved data from a second citizen science project, called Coordinated Avifaunal Roadcounts, involving bird counts along transects.
Hofmeyr SD, Symes CT, Underhill LG (2014) Secretarybird Sagittarius serpentarius Population Trends and Ecology: Insights from South African Citizen Science Data. PLoS ONE 9(5): e96772. doi:10.1371/journal.pone.0096772
Many more countries have Breeding Bird Atlas programs as well as some type of bird census along transects. These volunteer efforts are widespread because people adore birds. People know the common names of birds, their songs, how to attract them to backyards, where to place birdhouses to attract birds to nest, and which will be around for the winter and when to expect the rest to arrive from spring migration. Our intimacy with birds has resulted in avian research being iconic for citizen science. We know which species are in trouble because so many people watch birds and share their observations. Citizen science will also be part of how we figure out how to get the vulnerable species out of trouble.
Across the world, Breeding Bird Atlas programs involve systematic surveys in an area that gets divided into blocks, whether across a country, a state, or a province. Each block is surveyed by volunteers. For example, the entire state of New York was divided into 5,332 blocks, each 5 x 5 km (3 x 3 mi). Over 1,000 volunteers visit various habitats within their assigned block(s) and record evidence of breeding birds. The New York State Breeding Bird Atlas takes 5 years to complete. It was first done from 1980-1985 and again from 2000-2005. The first Atlas provides a treasure trove of baseline information. The second generation Atlas provides a gold mine of information about population changes.
There are over 10,000 species of birds in the world, over 650 of which breed in the United States. The second Atlases in New York, Ontario and Canadian Maritime Provinces revealed a declining trend among species of swifts, flycatchers, swallows, and nightjars. These birds have one thing in common: they catch insects while flying.
The second generation Atlases provided confirmation of the declines which researchers first spotted in 1993 when analyzing trends in the Breeding Bird Survey. The BBS is a citizen science program that began in 1966, prompted by Silent Spring and awareness of problems from DDT. It is run by the USGS’s Patuxent Wildlife Research Center and Environment Canada’s Canadian Wildlife Service. Every June, thousands follow the protocol that involves sampling along over 4,000 randomly established roadside routes. Each survey route is 24.5 miles long with stops at 0.5-mile intervals. People carry out a 3-minute point count at each stop and so a route takes about 5 hours to complete. During a point count, volunteers record every bird seen within a 0.25-mile radius and every bird heard.
More recently, in 2010, researchers looked again, in more detail, at BBS trends. They noticed the strongest declines in aerial insectivores have been in the northeast and that the steepest drops began in the mid-1980s.
Citizen science tells us, repeatedly, that aerial insectivorous birds are in trouble.
A common approach to creating good bird habitat involves a 3-prong approach of food, water, and shelter. So, the cause of aerial insectivore declines could be related to food, suggesting there are declines in insects. Or the problem could be more complicated. After all, the 3-prong habitat formula, while sufficient for animals in a zoo, may not be sufficient for wild birds. Wild birds need to communicate, to escape predation, to be in sync with the phenology (timing) of the environment, and to locate the food, water, and shelter. Namely, they need to sense their environment. Human activities that produce light at night and noise create sensory pollution.
Living indoors makes it difficult to appreciate the enormous change that artificial lighting has brought to the planet. Cities and suburbs are hundreds of times brighter than natural night skies. The brightness of cities casts a skyglow that affects surrounding areas. In city centers, you are lucky to see 20 stars, which means the sky is hundreds of times brighter than natural. Because of skyglow, even in the suburbs only 250 stars might be visible, which is still only 1/10th of what would be visible under natural skies. In the past, clouds made the sky darker, but now cloudy nights make the sky brighter because they reflect back the artificial light. We are only beginning to understand how these changes are affecting life on the planet.
Many people are aware that lights at night can be a problem for birds during migration. The lights are disorienting and can cause collisions. But fewer people may know that lights at night can be a problem for all organisms if these lights affect circadian rhythms. All organisms have biological clocks that allows them to tell time. These clocks synchronize (entrain) with day-night cycles. To figure out how light at night affects nesting birds, we need detailed information from across the country on the timing of bird reproduction, such as when they build nests, lay eggs, when chicks hatch, and when chicks fledge. Volunteers are providing this information through a citizen science project called NestWatch, which is administered by the Cornell Lab of Ornithology.
This year, we are carrying out a pilot study encouraging more people to report observations on one particular aerial insectivore, the Barn Swallow.
Barn swallows typically nest on structures built by people, such as barns and bridges. We know that it can be difficult to look into barn swallow nests. Most are too high, so unless you put a mirror on broom stick (or ceiling as in the photo), you can’t view the contents of the nest. But observant people can figure out a lot about the nesting phase, even from watching from the ground.
Near the structures where barn swallows are nesting, we are also asking people to estimate light pollution through another citizen science project called Globe at Night. The goal is to start getting some baseline data on the reproductive efforts of barn swallows across the country and those patterns in relation to light pollution.
I think we adore birds partly because we envy their abilities. They sing and they fly. Two skills that most people do not have. Aerial insectivores are particularly enviable: they fly and eat at the same time. The observations of bird watchers pooled into the Breeding Bird Atlas and the Breeding Bird Survey have collectively informed us of declines in aerial insectivorous birds. Now through a combination of other citizen science efforts, NestWatch and Globe at Night, we will piece together an understanding of the phenology and pace of the nesting cycle under different amounts of skyglow. This is a first step in understanding a piece of the larger puzzle of aerial insectivore declines.
Photo credits: Secretarybird by Yoky; Barn Swallow chick by Julie Hart; Barn Swallow eggs in mirror by Jody McBeath.