Diet composition based on stable isotopic analysis of fecal samples reveals the preference of Black-faced Spoonbill (Platalea minor) for natural wetlands and fishponds

Abstract

The Black-faced Spoonbill (<em>Platalea minor</em>; BFS) is a globally endangered species that is distributed only in the coastal zones of East Asia. Xinghua Bay is one of the main wintering sites and migration stopovers of BFS in mainland China. However, with the reduction and degradation of natural wetlands, it is uncertain whether artificial wetlands can provide habitat for the endangered BFS. Research on the diet of BFS will help to understand their preferences between natural and artificial wetlands and provide a reference for their conservation and habitat restoration. From December 2017 to February 2020, 45 potential food samples and 199 fecal samples of BFS were collected during six sampling periods, of which Cyprinidae, Mugilidae, Portunidae, Gobiidae and Palaemonidae were collected from natural wetlands and Crucian (<em>Carassius auratus</em>) and whiteleg shrimp (<em>Litopenaeus vannamei</em>) were collected from fishponds. Their stable isotope values (e.g., δ¹³C and δ¹⁵N) were measured to obtain the food composition information for BFS. In early winter, the proportion of Palaemonidae in BFS food was as high as 74.4%, while those of other foods were only 3.0% to 6.0%. In late winter, the food contributions for BFS were as follows: Portunidae 39.3% > Palaemonidae 26.1% > Cyprinidae 8.8% > Mugilidae 8.5% > Gobiidae 7.3% > Crucian 5.1% > whiteleg shrimp 4.8%. The proportion of Portunidae exceeded that of Palaemonidae, and together with Palaemonidae, it became the main food of BFS in late winter. The diet compositions of BFS between early and late winter were significantly different, which may be due to seasonal changes in food resources. Natural wetlands are the main feeding grounds of BFS, but fishponds also provide them with supplementary feeding grounds and resting places. Fishponds play an important ecological function in maintaining the overwintering population of BFS in Xinghua Bay.