GPS tracking reveals temporal patterns in breeding season habitat use and activity of a globally Near Threatened wader, the Eurasian Curlew

The Eurasian Curlew Numenius arquata is globally Near Threatened and considered one of the UK’s most pressing avian conservation priorities. Designing effective conservation interventions requires knowledge of the habitat requirements of breeding Curlews. However, aspects of the species’ breeding ecology, for example habitat use by off-duty breeding birds, remain poorly studied, partly due to difficulties in tracking bird movements. Here, we present the results of a pilot study using GPS tracking devices and dynamic Brownian Bridge Movement Models to elucidate patterns of habitat use and activity in three adult Curlews breeding in an upland area of the UK. Two adults tracked during incubation were active away from the nest in the evening and at night, when they preferentially selected areas of improved grassland up to 1.6 km from the nest, presumably to forage. Another individual tracked during chick-rearing was active during daylight hours and remained closer to the nest throughout the tracking period, with no evidence of use of improved grassland, despite this habitat being available close by. These results suggest complex and temporally heterogeneous patterns of habitat use in breeding Curlews. Data of this type, particularly if based on larger sample sizes, could be used to inform the design of conservation measures, for example the spatial scale over which habitat mosaics should be provided in agri-environment schemes. These tracking methods provide a useful method for further detailed studies, although birds’ reactions to tagging should be assessed and reported, particularly for new techniques.