#Shoebill stork florida drivers

Shoebills have a declining population trend, due to habitat degradation and loss, illegal bird trade and disturbance by humans 31, 32. The Shoebill is a large long-lived species, categorised as Vulnerable by the IUCN. The Shoebill ( Balaeniceps rex) is an iconic wetland specialist, with a patchy distribution in central-eastern Africa, from South Sudan to Zambia 30, 31. More recently, this index has been used to map surface water for animal movement studies 12, and to identify suitable habitat and inform area protection for shorebird species 29.

The NDWI delineates and highlights open water by distinguishing it from vegetation and bare soil, and has mostly been used to map waterscapes in urban settings 27, 28. The Normalized Difference Water Index (NDWI) proposed by McFeeters 26 is an index that uses remotely sensed imagery to map surface water. Indices based on satellite imagery have been increasingly used to interpret environmental conditions and infer ecological processes 23, 25. Such information has only been available relatively recently, through the integration of data from GPS trackers with remotely sensed environmental data 23, 24, 25.

#Shoebill stork florida drivers

Understanding the drivers of movement of long-lived birds relies on information on the spatial and temporal dynamics of movement at different ages in relation to environmental variables. This has unravelled differences between adults and juveniles in space use 15, 16, habitat selection 14, 17, and timing 18, 19, 20 and efficiency of movements 20, 21, 22.

The way individuals explore the environment can change as they age 14, 15, and recent advances in GPS tracking technology and increases in device longevity, have enabled the detailed study of individual movements for several years or even throughout lifetimes. In tropical systems with strongly seasonal environments, prolonged periods of drought followed by extreme floods can lead to striking changes in habitat suitability 9, 11 and drive the large-scale movements of waterfowl 12, due to fluctuations in the abundance and availability of foraging resources 13. In wetlands, the distribution of surface water is one of the main determinants of species’ spatial distribution 6, 7, 8 and individual movements 9, 10. Changes in the environment can alter resource distribution, which consequently determines animal migratory 1, 2, 3 and, local, movements 4, 5. One of the key challenges in ecology is to understand how environmental fluctuations drive animal movements. Our study highlights the need to understand the movements of Shoebills throughout their life cycle to design successful conservation actions for this emblematic, yet poorly known, species. We hypothesise that the different responses to changes in surface water by immature and adult Shoebills are related to age-specific optimal foraging conditions and fishing techniques. However, there were no differences in NDWI of areas used by Shoebills before abandonment and newly selected sites, suggesting that Shoebills select areas with similar surface water.

Immature and adult Shoebills responded differently to changes in surface water sites that adults abandoned became drier, while sites abandoned by immatures became wetter. However, average annual home ranges were large, with high individual variability, but were similar between age classes. We show that Shoebills stay in the Bangweulu Wetlands all year round, moving less than 3 km per day on 81% of days. We relate their movements at the start of the rainy season (October to December) to changes in Normalized Difference Water Index (NDWI), a proxy for surface water. Using GPS transmitters deployed on six immature and one adult Shoebills over a 5-year period, during which four immatures matured into adults, we analyse their home ranges and distances moved in the Bangweulu Wetlands, Zambia. This study is the first to examine the movements of Shoebills ( Balaeniceps rex), an iconic and vulnerable bird species. For wetland specialists, the seasonal availability of surface water may be a major determinant of their movement patterns. Animal movement is mainly determined by spatial and temporal changes in resource availability.