PhD defence Ms Mitra Shariati Najafabadi

Department of Natural Resources


Title of defence

Migration timing and stopover selection for Barnacle Geese Branta Leucopsis


Timely arrival at the breeding site is particularly important for the migratory avian herbivores to breed in the Arctic region, and it depends on both environmental parameters at the breeding site, and those at the stopover sites. Relatedly, it is imperative that migration commences at the right time and avian herbivores are tuned to a wave of available forage as they move along the migration flyway, i.e. the so-called “green wave” hypothesis. In the current study, the focus was barnacle geese Branta leucopsis that are categorized in the highly selective herbivores class, and are depending on forage of high nutritional quality. The green wave hypothesis has been successfully tested for barnacle geese using field data. However, there are several proxies evidencing the onset of spring that one of them is satellite-derived green wave index (GWI). In addition, GWI is closely related to photosynthesis and has been proved to be a useful tool to study the migration of herbivorous mammals with respect to vegetation phenology. However, it has never been tested for migrating avian herbivores.
Besides following the food availability at the stopover sites, migratory birds need to respond to other environmental parameters such as weather, temperature and day length to anticipate the most favourable arrival date at the breeding site. In particular, environmental parameters at the last staging site may highly influence the arrival date because it is the longest and closest stopping site to the breeding ground. Despite the possible importance of environmental parameters at the last staging site, little or no knowledge exists about the relations between these parameters and the migration timing of the geese.

In addition to migration timing, stopover ecology is also an area of avid interest in avian ecology. The stopover selection along the migratory route is important for long-distance migrants to renew their energy reserves for completing their migration. Moreover, the habitat selection is greatly influenced by a variety of environmental parameters including food availability and the costs related to predation or disturbance risks, and inter- and intraspecific competition. Thus, the relationships between the species and their environment can be understood through studying habitat selection using modelling. This information is necessarily required for effective conservation and management of migratory birds. However, it is evident that there is a lack of knowledge about the site selection of migratory birds.

Barnacle Goose seen in Enschede

The main goals of this thesis are: 1) to investigate the effect of green wave of highly nutritious plants and environmental parameters along the flyway and particularly at the last staging sites on spring migration timing of barnacle geese, and 2) to model the stopover site selection of barnacle geese using Bayesian expert system and environmental parameters. To reach these goals, the advance applications of statistical analysis plus remote sensing and satellite tracking techniques are applied.

Using GWI, the results presented in this thesis showed that individual barnacle geese surf the wave of high-nutrition plants. Moreover, it was found that GWI is a more accurate index as compared to temperature-derived green wave index for prediction of the arrival dates of barnacle geese at stopover and breeding sites. Besides, the obtained results revealed a significant correlation between the environmental parameters at the last stage of migration and arrival date at the breeding site. Barnacle geese may benefit from using the local environmental conditions to adjust their migration timing; however, they may not be able to predict the situation at their destination from their last staging site.

Moreover, during the research and by incorporating environmental parameters into a Bayesian expert system, it was observed that this model can correctly detect the stopover sites of the geese. This model can be used as a proper method for modelling the presence/absence of barnacle geese at the stopover sites in the future.

These findings enable the investigators to monitor the effect of future climate change on migration timing of the geese. Furthermore, the correct identification of stopover sites is particularly important in management plans to resolve possible future conflicts caused by an increase in numbers and range of barnacle geese.


Mitra Shariati was born on 19th September 1983 in Najafabad, Isfahan, Iran. She studied Natural Resource Engineering-Environment at the Isfahan University of Technology and received a B.Sc. in September 2006. She obtained her M.Sc. in the same field from the University of Tehran in February 2009. Her M.Sc. research focused on avifaunal distribution pattern and abundance in Hyrcanian mountain forests in northern Iran. After graduation, she started to collaborate with the University of Tehran on a number of environmental projects for two years. In 2011, she was awarded the European Commission, Erasmus Mundus scholarship to pursue her doctoral research at the Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, which resulted in her doctoral thesis “Migration timing and stopover selection for barnacle geese Branta leucopsis”.

Event starts: Thursday 23 March 2017 at 14:30
Venue: UT Waaier 4
City where event takes place: Enschede

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