Settlement of Redshank Tringa totanus following winter habitat loss: Effects of prior knowledge and age

Abstract

The ability of animals to survive habitat loss is likely to be dependent not only on the proximity of alternative habitat but also on the ability of individuals to relocate. Here, we examine influences on the settlement behaviour of Redshank Tringa totanus following winter intertidal habitat loss resulting from the construction of a barrage at Cardiff Bay, on the Severn Estuary, UK. Results supported previous studies showing that the species is highly faithful to its wintering sites. Redshank were reluctant to leave Cardiff Bay in the first winter following habitat loss: birds used the site at all tidal stages for eight days after barrage-closure and thereafter continued to roost there. Birds moved at most 19 km, the distances that individuals moved being inversely related to their age, indicating that young birds were less attached to the bay and so more plastic in their response to change. Settlement also appeared to be influenced by prior knowledge - notably, one site previously only used nocturnally by 'Cardiff Bay' birds was used diurnally post-closure despite being heavily disturbed during the day. Birds initially ranged more widely following their displacement, but over the three winters post-closure, became increasingly concentrated into one recipient site, just 4 km from the bay. It is suggested that individuals' fidelity to Cardiff Bay post-closure and lack of knowledge of alternative foraging sites would have been to their detriment.