15/05/18 - Egret abundance

Over the last month we have seen an increasing number of Grey Herons around the reserve as birds in the local heronry are busy feeding hungry broods. We’ve been avoiding any disturbance to the heronry in March and April, following the cold weather in March whilst the adults were incubating (herons can be sensitive to any disturbance at this critical time), but during late April and early May we have been visiting the heronry to survey the number of active nests, as we have done for the BTO’s heronry census for nearly 40 years. This national survey has been running for 90 years and has built up a wealth of data and knowledge on the population trends of our UK Grey Heron population. On our first visit the numbers of herons appear down with just 19 nests so far – whether this is the effect of the cold spell in early March which may have taken its toll, or merely delayed breeding, or the effects of the extensive late spring flooding reducing feeding opportunities, we’ll have to wait and see.

However, this year it isn’t only the herons that we’ve been keeping an eye on, several (and an increasing number) of pairs of Little Egrets are also present – a species which has been abundant in the valley recently, with a high count of 42 of late. Little Egrets are an increasingly familiar sight in the Lower Derwent Valley these days and are now often more regularly encountered than our resident Grey Herons, especially at Bank Island where birds can currently be seen on a daily basis. In particular over the last month they have been recorded far more than herons, with good concentrations at Bank Island, Wheldrake and North Duffield Carrs, with some notable counts also coming from Sutton Ings and the Low Grounds as well as along the Pocklington Canal.

The first recorded sighting in the valley came in 2001 with the first record of breeding occurring several years later in 2009. Last year numbers increased to at least eight pairs, however this year’s figures look set to be a huge increase on that – more details to follow later in the season. Recently another colour-ringed individual was seen at Bank Island (awaiting details), so please remember to look out for any birds with rings on as this helps us to build up a picture of where ‘our’ local birds are coming from and going to.