The method of habitat assessment for crab-feeding birds on tidal flat by Habitat Suitability Index models for the burrowing crab Macrophthalmus japonicus

Abstract

The objective of this study was to develop a method for assessing tidal flat ecosystems. We focused on crab-feeding birds, the top predator on tidal flats. Distribution of mud flat crabs is generally affected by substrate conditions, such as grain size and soil water content. Therefore, habitat suitability for crabs is likely able to be evaluated by measuring substrate condition. We documented the distribution of the burrowing crab Macrophthalmus japonicas, and developed two Habitat Suitability Index （HSI） models based on 1） the number of crabs and 2） their burrows. Scores of the two HSI models for the crab were both correlated with the number of individuals of two crab-feeding snipes （Heteroscelus brevipes and Numenius phaeopus）. Our results suggest that the distribution of crab-feeding birds can be assessed based on habitat suitability for their prey.