Birds and their habitat conditions in reed marshes with different cutting intervals at Chongming Dongtan along China’s coasts

Abstract

Reed marshes are vital habitats for many species of birds, some of which are wholly or largely dependent on this habitat. Reed harvesting in winter is a common practice for increasing economic benefits, but it also promotes reed growth and maintains reed marsh landscapes by removing dry reed stalks. Different reed cutting intervals create different habitat conditions and thus lead to differences in habitat use by marsh birds. Although many studies have reported birds and their habitat conditions in reed marshes with different cutting schemes in Europe, few studies have been conducted in Asia, where reed marshes are widely distributed. Here, we conducted a one-year survey (from March 2019 to February 2020) on birds and their habitat conditions (vegetation and food) in reed marshes with three cutting intervals: age 1 (cutting every year), age 2 (cutting with one-year interval), and uncut (uncut for four years), at Chongming Dongtan, an estuarine wetland on China’s coast. As the cutting interval increased, the growing reed density decreased, the dry reed and total reed density increased, and the food density (in terms of reed seeds, arthropods, and arthropod eggs) decreased. A total of 4627 birds of 23 species were captured by mist nets. In general, species capture rates were similar among the three habitats in the same season, and individual capture rates in uncut reed marshes were lower than those in age 1 and age 2 marshes. This was probably because the relatively low density of reed stems promoted the movement of birds to age 1 and age 2 marshes, where birds could find abundant food. In contrast to previous studies, we found that age 1 marshes provide suitable habitats for birds soon after vegetation is restored in summer. However, reed parrotbills (Paradoxornis heudei), a common reed marsh specialist, had high capture rates in uncut reed marshes in winter. This is probably because they live in dense vegetation, and dense vegetation can reduce threats from aerial predators. This study emphasizes that habitat use should be considered in reed cutting practices and that a mixture of reed marshes with different cutting intervals benefits different birds and also different requirements of the same birds over the course of the year.