Published: 23 September 2013 at 15:05
Anglia Ruskin study finds woodland blue tits and great tits struggled during cold, wet 2012
Birds breeding in native British woodland are more susceptible to the effects of extreme weather conditions than those in urban environments, according to a new study published by online science journal PLOS ONE.
The research, led by scientists at Anglia Ruskin University and the Centre for Ecology and Hydrology, examined breeding patterns of blue tits and great tits in Cambridgeshire over a 10-year period.
The scientists discovered that birds breeding in urban areas are better able to cope during unusually cold and wet weather because they are less reliant on feeding their chicks a single food source. The study compared 2012 – a year with temperatures significantly lower than average, including a particularly cold and wet spring – to the previous nine years.
Of the three sites monitored, the birds at Brampton Wood nature reserve (a typical mixed deciduous woodland of common ash, English oak and field maple) struggled most during 2012, the wettest year in England since records began in 1910.
The other sites surveyed were the Cambridge University Botanical Gardens in Cambridge city centre and Cow Lane nature reserve, a mixed riparian zone of willows and reed beds close to the banks of the Great Ouse.
Both the number of chicks in the brood and their individual weights were lower than normal across all sites in 2012, but the most significant decrease was seen in the traditional woodland habitat of Brampton Wood.
Usually, blue tits and great tits lay one egg per day until their clutch is complete and then begin to incubate them. However, the Brampton Wood birds delayed their incubation in response to the onset of cold weather, which in turn delayed chick hatching.
This prolonged stalling of the nesting cycle was unprecedented during the 10-year period of the study at any of the sites and was likely due to the negative effect of the cold on the woodland bird’s caterpillar prey.
For great tits, the period from laying the first egg to hatching was 32 days tits at Brampton Wood, a period almost twice as long as the urban site (17 days). Typically, a long delay in hatching leads to a smaller brood size and fewer chicks successfully leaving the nest.
Dr Nancy Harrison, Senior Lecturer in Life Sciences at Anglia Ruskin, said: