Macro-demography of North America’s migratory avifauna

Reversing the global loss of biodiversity is a primary challenge of our time, however the reasons for species declines are often poorly understood. Birds exemplify this crisis, with the North American continent supporting 3 billion fewer birds today than in 1970. Migratory birds are particularly hard hit. These birds travel vast distances between their wintering and breeding grounds, making it difficult to pinpoint where threats exist and where conservation efforts should be focused. To understand current bird declines, researchers require accurate estimates of the birth and death rates of birds across the vast geographic areas they visit. However, such information is currently only available for a few select locations during short periods of the year.

This research will address these challenges by developing novel tools to measure the recruitment and mortality rates of birds across an entire continent and throughout the whole year. The insights generated by these efforts will help us to understand which factors have been causing population declines. In particular, we will investigate how extreme climatic events such as heat waves and cold spells have affected the annual variability in birth and death rates. Explaining such year-to-year changes in bird populations sizes will be a critical step towards understanding long-term bird declines. By gaining insight into the limiting factors underlying population fluctuations, this work aims to sustain the vital ecological, economic, and social services that birds provide to humans and the environment.

To create these new analyses, we rely on three novel ‘big data’ resources to track bird populations throughout the year. First, the US weather radar network (NEXRAD) is used to study the flow of migrants into and out of North America during fall and spring migration. Comparing these numbers between adjacent seasons will enable us to estimate the birth and death rates of all migratory birds combined. Second, observations from hundreds of thousands of volunteer citizen scientists (eBird data) and dynamic species distribution models will be used to track seasonal variation in the numbers of birds recorded. This resource captures species-specific patterns that are not available from the radar data. Third, remote sensing data and the National Ecological Observatory Network (NEON) will be used to understand temperature and phenological extremes, which will be explored as a mechanism driving population changes. Overall, this research aims to develop the tools to understand current population declines and point towards a roadmap for the recovery and conservation of the mass migration of birds.

NSF Award #2017817

Relevant publications:

1. Dokter AM, Farnsworth F, Fink D, Ruiz-Gutierrez V, Hochachka WM, La Sorte FA, Robinson OJ, Rosenberg KV, Kelling. (2018) Seasonal abundance and survival of North America’s migratory avifauna determined by weather radar, Nature Ecology and Evolution 2 (10), 1603, DOI 10.1038/s41559-018-0666-4
2. Rosenberg KV, Dokter AM, Blancher PJ, Sauer JR, Smith AC, Smith PA, Stanton JC, Panjabi A, Helft L, Parr M, Marra PP. (2019) Decline of the North American avifauna. Science, 366, 120-124, DOI 10.1126/science.aaw1313
3. Fink D, Auer T, Johnston A, Ruiz‐Gutierrez V, Hochachka WM, Kelling S. (2020) Modeling avian full annual cycle distribution and population trends with citizen science data. Ecological Applications, 30(3):e02056, DOI 10.1002/eap.2056

The BirdCast site recently got a beautiful redesign on Sept. 1 2020. Check it out at https://birdcast.info!

For the project I develop and maintain the live migration maps. The maps show you every night the numbers and flight directions of birds in the air.

From the annual biomass passages, long-term trends were estimated, which indicate a large decrease in the number of birds migrating at night over the US.

The total loss in spring passage since 2007 was estimated at 14 +/- 9%. Similar steep declines were found from a comprehensive compilation of ground surveys, including the North-American Breeding Bird Survey, which indicate a loss of 3 billion birds in North America since 1970, or 1 in 4 birds.

The study was published in Science on 4 Oct 2019. Visit https://www.3billionbirds.org/ to download the paper and for more information on the study.

literature

1. Rosenberg KV, Dokter AM, Blancher PJ, Sauer JR, Smith AC, Smith PA, Stanton JC, Panjabi A, Helft L, Parr M, Marra PP. (2019) Decline of the North American avifauna. Science, 366, 120-124, DOI 10.1126/science.aaw1313

Eelgrass beds are a restricted and endangered habitat around the world. After the decline of eelgrass beds in the Dutch Wadden Sea, the Brent goose population initially collapsed, but recovered later due to conservation actions and a habitat‐switch towards lower salt marsh vegetation and agricultural fields. Recently, the population has declined again following a long series of poor breeding years. Brent geese were among the first migratory species for which it was shown that spring conditions in the temperate region carried over to breeding performance in the Arctic. Recent evidence suggests that the quality of wintering and stopover sites may be vitally important to population processes in migrants.

In this project, I investigate the importance of non‐breeding habitats, eelgrass beds in particular, for Brent goose population dynamics and individual fitness, relative to the importance of alternative habitats. We equiped in total 30 birds with GPS trackers both on the island of Terschelling and the island of Schiermonnikoog in the Dutch Wadden Sea. The tags record the birds’ geographic position and activity every hour year-round, which reveals in detail the habitat use of the Brent geese along their flyway.

The project is funded by the Wadden Fund project Metawad‐1. Metawad‐1 is a 5-year research program carried out by a consortium made up of NIOZ, the University of Groningen, The Netherlands Institute of Ecology (NIOO), The Nature Information Foundation (Stichting Natuurinformatie) and the Dutch Centre for Field Ornithology (SOVON).

The first year-round migration tracks for 10 individual Dark-bellied Brent Geese, in relation to the retreating snow and ice cover:

In the paper Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues? the behaviour is described in detail, and alternative hypotheses are formulated regarding the functional significance of the ascents.

For further information also see this press release