Below are some of the questions we wanted to try and answer:
- Where do the birds go during the day
In an attempt to answer some of these questions, since 2004 a total of 100 Whimbrel have been caught and colour-ringed at the Lower Derwent Valley NNR spring roost. Several birds have been radio-tracked and four have been fitted with satellite trackers.
- Birds tend to feed locally to the roost site, often within 2-3 km, on semi-improved grassland but perhaps (and most significantly) on one specific soil type.
- Individual birds tend to spend 8-10 days at the roost, at which time they almost double their body weight (arriving at about 300-350g and leaving 550-600g - 8 days later!).
- They are very site specific - often returning year after year to the exact same roost site and the exact same feeding fields nearby. Not only that but they appear to do so with amazing regularity, often turning up on the same date every year - keep watching our blog updates over the coming weeks to follow this years Whimbrel story. The first birds of the spring roost have usually (for the last five years) appeared on 16th April (next Monday), although Dave had what was almost certainly 4 passage birds at the site at dawn on Tuesday of last week (11th).
- Birds appear at the roost (best viewed from Swantail Hide) around sunset (7.45 to 8.25 pm) - smaller numbers of birds may be found during the day when they move onto Wheldrake or Bank Island (occasionally North Duffield) for a drink and wash, although this is more frequent towards the end of the passage period.