News From the Ouse Washes - Spring 2010

A frozen reserve in early January

Winter Flood levels explained:

Water levels in the winter months at the Ouse Washes are a crucial factor to determining our duck and wader numbers; because of this, we record the water level on a daily basis. When the water level is low, (less than 0.5 metre) the reserve does not flood. When the water level is high, (over 2 metres) it is too deep for many of the dabbling wintering duck and there is no available land for the waders to feed. Unfortunately, the flood levels are beyond the control of the RSPB and are related to rainfall (and snowfall) in the Great River Ouse catchment area in Cambridgeshire, Bedfordshire, Buckinghamshire and Northamptonshire.
This winter the reserve did not begin to flood until the start of November. Throughout November and early December, the level was ideal. An ideal water level is when the lower lying washes near the hides begin to flood, perfect for the dabbling ducks (teal, gadwall, shoveler), the ditches and rivers can support the diving ducks (tufted and pochard) and the dry tops of the washes provide a food source for grazing wigeon and feeding waders.
However, by 11th December the flood level peaked at 2.49 metres. The washes were now in a deep bank-to-bank flood, with limited space for feeding waders, wigeon and other dabbling duck. In addition, the few suitable areas remaining are on the far side of the reserve, so views from the hides are distant. However, the deeper water level does mean there are increased areas for the diving ducks. Since December, the flood level has only been recorded as less than 2 meters on three days! This is reflected below in the peak winter bird counts – I have included the five-year averages in brackets for      comparison and the only species recorded above/close to the five-year average are mallard, pochard, and coot.

Wigeon 24,175 (31,287), gadwall 490 (1095), teal 2492 (5017), mallard 3336(2868), pintail 734(1864), shoveler 288(1128), pochard 3151(2786), tufted duck 1288 (2158), coot 4053 (4467), lapwing 7340 (12,953), black-tailed godwit 809 (2394). However, there is a chance that some of these peaks, particularly black-tailed godwit, may increase in the late March counts.

Other birds of note included bittern, 38 white-fronted geese, two short-eared owls, three hen harriers and six water pipits.

When we talk about wild swans at the Ouse Washes, we are referring to the Bewick’s Swans that breed in Russia and the whooper swans that breed in Iceland. The Ouse Washes and surrounding arable land are an important area for both these species as they support about 45% of the wintering British whooper swans and 80% of the wintering British Bewick’s swans. The swans use the reserve to roost on in the evening and feed out on the surrounding arable during the day. This means we have two methods to monitor these birds. We attempt to count them at dawn on the reserve – at times this is not accurate as we only have about half an hour between it being light enough to distinguish the different species and too light so that they fly off to feed! However, we also count them feeding on the arable during the day – this can produce more accurate results as the birds tend to be stationary for longer but we need to ensure that we can find them in the first place! The arable count also allows us to record the number of young in a family. The peak counts from the two methods resulted in 5632 whooper swans and 5109 Bewick’s swans – both above the five year average.  The number of whooper swan juveniles peaked at 13%, which is about average compared to previous years. The  number of Bewick’s swan juveniles peaked at 9%, which is higher than the last few years but still lower than average.

Alex Thomas - Warden