Not only was winter 2015–16 the warmest ever for England and Wales, mostly due to exceptionally high temperatures in December 2015, it was also the wettest on record in Yorkshire.
Spring temperatures were more normal, being slightly below average in April and slightly above average in May. Rainfall during the breeding season varied dramatically between counties and months, with the heaviest rainfall in northern England and Scotland being limited to April. In July and August the trend reversed, with above average rainfall in the north but exceptionally dry conditions in the south, where summer temperatures were also above average.
All of this meant that it was a mixed year for our resident birds. A lot depended upon the time of year they chose to try to breed. Blue Tits in particular produced below average clutch sizes which led to a reduced number of chicks being fledged, and Great Tits did little better. With total numbers down by a tenth and the number of young they produced last year down by over a third, Blue Tits in particular, are having a hard time. This has been apparent in our gardens since with lower numbers around than usual.
The mild winter of 2015–16 with little or no snow cover, meant that ground feeders such as Song Thrushes, Robins and Dunnocks, as well as Wrens, which are all particularly sensitive to harsh winter weather, survived in larger than usual numbers. Again this is apparent in most of our gardens, although Song Thrushes are still far from common.
Blackbird data suggest that the number of fledglings in 2016 was around 20% lower than average too, though at the moment with migrants from central Europe still here, the effect is difficult to assess.
Yet again there was a late start to the breeding season. Laying dates for six resident passerines, including both Blue and Great Tit, were delayed by between five and ten days in 2016, with low temperatures in early spring being the most likely cause. House Sparrows, which unlike most tits make several breeding attempts, may well have taken advantage of the fine late summer weather to produce a greater than average number of fledglings.
BTO results reveal that 17 out of the 24 bird species followed by their Nest Recording Scheme exhibited significant decreases in productivity in 2016
relative to the average of the previous five years. For some of these species (Blue Tit, Blackbird) a reduction in the number of young successfully fledged may be responsible for this decline; for the Blue Tit the mechanism appears to have been a reduction in clutch size, this being the lowest recorded since in 1939. Other surveys suggested that the wet conditions mid-summer also reduced post-fledging survival rates, mainly due to less food being around for these largely insectivorous species.
With a cold snap on its way, keep a sharp eye on your garden; you never know what might turn up!
If you find the lives of our garden birds to be of interest, and would like to join in and count the feathered occupants of your garden, please contact me or visit the BTO Garden BirdWatch website (www.bto.org/gbw). If you know of a local organisation who would like a talk on garden birds call: Mike Gray 07596 366342 or firstname.lastname@example.org.