Feedback links between plasticity of bird migration strategies and population dynamics

Migration is a resource-tracking strategy evolved by birds in a seasonally changing environment.
However, the feedback process between the plasticity of migration strategies and the dynamics of migratory bird populations remains unclear
.
Bohai Bay is located on the East Asia-Australasian migratory bird migration route, supporting the survival and development of more than 200 million migratory waterbirds.
Every spring and autumn, a large number of waterbirds are recorded to stop and replenish energy during their migration
.
Recently, the team of Professor Zhang Zhengwang of Beijing Normal University used more than ten years of waterfowl monitoring data to start from the loss of migratory birds during the migratory stop, and for the first time revealed the feedback link between the migration strategies and population dynamics of birds
.

By constructing an individual-based model that includes stylized migratory populations, this study proposes for the first time a hypothesis on how changes in migratory stops drive changes in individual residence time and population dynamics of migratory birds.
This hypothesis was verified by the survey data of migratory water-stopping birds in the Bohai Bay area of ​​China
.
The study found that the loss of the stopover area will lead to changes in bird migration strategies.
As the food resources available to the individual migratory birds in the stopover area are reduced, they will prolong their stay in the stopover area to replenish energy.
The increase in population densities of migratory birds during the interim period has a knock-on effect on population dynamics during the reproductive and wintering phases of the life cycle
.
This is because the loss of stopovers during migration not only leads to a decline in the environmental carrying capacity of the entire migration route, but also changes the stage in the life history of migratory birds that regulates the population
.

The results show that the effect of environmental change on a certain stage in the life history of migratory birds can have a huge impact on the population dynamics of the entire life history cycle through its phenotypic plasticity
.
Therefore, only by studying all stages of the entire life cycle of migratory birds can we deeply understand the population dynamics of migratory birds
.
Only focusing on the research of a certain habitat or a certain life cycle stage of migratory birds and ignoring other aspects of information will make us unable to accurately predict the dynamic changes of migratory bird populations, and even lead to wrong conclusions, thus missing the implementation of migratory birds.
The best time for protection
.
Not only does this study explain the dynamics of migratory birds in the East Asia-Australasian flyfield, but the feedback mechanisms we uncover can also serve as a general theoretical framework for studying other taxa and migratory systems
.

The research results, titled "Unravelling the processes between phenotypic plasticity and population dynamics in migratory birds", were published in the Journal of Animal Ecology , the flagship journal of international animal ecology
.
Liu Jin, a doctoral student at the School of Life Sciences of Beijing Normal University, is the first author of the paper, and his supervisor, Professor Zhang Zhengwang, is the corresponding author.
Among the collaborators are Dr.
Lei Weipan of Beijing Normal University, associate professor Mo Xunqiang of Tianjin Normal University, and professors of Oxford University, UK.
Professor Tim Coulson and Australian waterfowl expert Mr Chris Hassell
.
The research work was supported by the National Natural Science Foundation of China, the National Scholarship Council, the Fundamental Research Fund for Central Universities, the Alxa SEE Ren Bird Flying Project, and the Paulson Institute
.

Figure 1 The migratory waterbird colony in the mudflat wetlands of the Bohai Bay (photo by Zheng Wenzhong)

Figure 2 The migratory waterbirds and their habitats in the Beidagang Wetland in the Bohai Bay (Photo by Nian Aijun)

Figure 3 Feedback mechanism linking individual migration strategies and population dynamics (picture from the article)

(a) Changes in the environmental carrying capacity and the average daily density of the population with the size of the stopover
.
The circle size represents the environmental carrying capacity of each habitat, and the grey rectangles represent the maximum number of populations that can be carried over the entire annual cycle
.
In (a1), the size of wintering and breeding grounds determines the environmental carrying capacity of the entire migration route, while in (a2), the size of the stopover during migration determines the environmental carrying capacity of the migration route
.
The graphs show the daily average population density changes during the suspending period in the remaining migratory suspending areas (i.
e.
, the S1 area) in the cases (a1) and (a2), respectively
.
(b) Feedback mechanism between individual dwell time and population density of migratory birds
.

Paper link: https://besjournals.
onlinelibrary.