A lack of suitable roosts increases the threat of intertidal foraging habitat loss to migratory shorebirds

Abstract The loss of intertidal foraging habitats at stopover sites is the primary cause of population declines in many migratory shorebirds. However, the absence of high‐tide roosts can exacerbate this impact by increasing the energy consumed for alarm flights and longer commutes between foraging and roosting sites, which have been poorly quantified during time‐constrained spring stopovers. We monitored alarm flights at roosts using camera traps and tracked the commutes between roosting and foraging sites of great knots ( Calidris tenuirostris ) and bar‐tailed godwits ( Limosa lapponica ) at Yalu Jiang Estuary, a critical stopover site for shorebirds in the North Yellow Sea. We analysed the energy costs of alarm flights by human disturbances and commuting using flight energetic models. Camera trap monitoring revealed that 20 of 67 (29.9%) roosting records at aquaculture ponds recorded human disturbance that resulted in alarm flights. Birds travelled 2.8 times farther than the optimal commuting distance when nearby high‐tide roosts were available. Flight energetic models estimated that alarm flights and extended commuting resulted in an additional energy expenditure of 355.9–902.3 kJ, equivalent to 3–4 days of foraging effort based on food intake rates. Synthesis and applications . Foraging sites and nearby high‐tide roosts are integral habitat components for shorebirds to acquire energetic surpluses, especially at migration staging areas. While protecting intertidal flats to provide foraging habitats for shorebirds, human activities should be minimised and disturbance should be avoided at aquaculture sites during the high‐tide periods of spring tides to provide safe roosts for shorebirds. Artificial roost structures (floating roosts, roost islands, etc.,) could also be an effective solution for providing additional roosting habitats for shorebirds.