Shoebills – Changes In Surface Water Levels Drive Their Movements
A newly published research report on our Bangweulu Shoebill looks into how environmental changes in their habitat, especially the seasonal availability of surface water, alters their movement patterns.
By analysing the movements of Shoebills in different life stages, and how these movements relate to available surface water (which is a key environmental factor for wetlands), the study’s goal was to improve ecological understanding of Shoebills to further assist future conservation efforts of this unique species.
Advances in GPS tracking technology has meant that studies on individual birds can take place over several years, and now throughout a bird’s lifetime. This has shown that juvenile and adult Shoebills use habitats differently, especially in their movements and habitat selection.
The research
Using GPS transmitters, fitted onto 11 Shoebills, researchers were able to track the Shoebill’s movements between December 2011 and October 2018, collecting 119,321 valid GPS positions. They obtained 47,134 GPS positions for 6 Shoebills tracked as immatures and 44,985 GPS positions of 5 Shoebills tracked as adults. During this time 4 immatures matured into adults, with researchers analysing home ranges and the distances they moved.
“The way individuals explore the environment can change as they age.”
The team found that these Shoebills stayed in the Bangweulu Wetlands all year round, normally moving less than 3 km per day. They have large home ranges although there was high individual variability, with immature and adult Shoebills responding differently to changes in surface water.
The sites that adults abandoned became drier, whilst sites abandoned by immature Shoebills became wetter. These differences might be because immature birds have different foraging techniques so need different feeding conditions compared to adult birds.
Shoebills
Shoebills (Balaeniceps rex) are an iconic wetland species, found in various locations in central-eastern Africa. They live in permanent swampy wetlands and seasonally flooded grasslands, hunting fish in shallow waters and using floating vegetation as fishing sites.
They are a large, long-lived species which are listed as ‘Vulnerable’ on the IUCN Red List. This is due to their declining populations – it is estimated that there are between 5000-8000 individuals left in the wild. Their decline is because of habitat loss, the illegal bird trade and disturbance by humans.
Shoebill habitats
The Bangweulu Wetlands is a typical Shoebill habitat, similar to the other regions that they live in. It undergoes dramatic changes in water levels between the dry breeding season and the wet season.
“One of the key challenges in ecology is to understand how environmental fluctuations drive animal movements. Changes in the environment can alter resource distribution, which consequently determines animal migratory and, local, movements.”
The distribution of surface water in wetlands areas is one of the key determinants of species’ spatial distribution and an individual movements. Tropical regions have changing seasonal environments – prolonged periods of drought followed by extreme floods. This can lead to major changes in suitable habitat for waterfowl, leading to large-scale movements due to fluctuations in the abundance of food.
Further research
The research team from the University of East Anglia, UK, University of Applied Sciences, The Netherlands and the University of Cape Town, South Africia recommend that more research is needed into a Shoebills life-cycle to fully understand their different habitat needs throughout their lives. This will then provide much needed knowledge for successful conservation efforts for this little known about species.
You can read the full research report Changes in surface water drive the movements of Shoebills at www.nature.com