Shorebird habitat selection and foraging behaviour have important implications for management at an internationally important non-breeding wetland.
Abstract
It is imperative to manage wetlands appropriately in the non-breeding range of migratory shorebirds because their habitat quality impacts survival and reproductive performance. However, it is challenging to measure and relate these parameters to the habitat quality of individual sites because they are influenced by a composite contribution to fitness across all sites used in the annual cycle. Identifying important habitat quality features for shorebirds, and assessing whether management actions aimed at improving habitat quality are effective, poses a substantial challenge. Nonetheless, within a site, shorebird subsite selection and foraging behaviour could reveal variation in habitat quality proxies and suitability. We developed a field study to investigate habitat selection and habitat quality proxies for shorebirds in the Coorong, an internationally important non-breeding site in Australia. We examined the abundance of shorebirds among multiple subsites in the wetland and their foraging behaviour in relation to multiple variables (potential habitat area, salinity, prey density, wind, temperature), the first three of which can be influenced by management. Larger potential habitat area, defined as the combined area of bare mud/sand and shallow water (<20 cm depth), was associated with higher shorebird abundance across subsites with the same shore length, suggesting this is the most important site feature for habitat selection. Shorebird step rate, which reflects the effort associated with catching prey, was higher at subsites with lower prey density. This suggests that step rate can be used as an indicator of prey availability. Potential habitat area is strongly positively correlated with shorebird abundance. At sites where water levels can be managed, flows should be regulated so that water levels are not too high (limiting habitat area) or too low (drying out mudflats). However, it is critical that large potential habitat areas that attract shorebirds are productive so that they do not become ecological traps. Management should aim to maintain healthy prey abundance on areas attractive for shorebirds, while also minimising predation and disturbance of shorebirds. Monitoring prey abundance directly can be challenging, but our study shows that shorebird step rate provides a low-cost indicator of relative macroinvertebrate prey abundance.