News from the riverside March 2022
Last month’s news from RB was about blackcaps wintering in the UK. As I had already prepared my March newsletter on the same topic, I think it still worthwhile ‘putting it out there’ as the research continues to unearth fascinating facts on this subject.
Spring is certainly on the way. Hurrah! As the weather improves, time out on the riverside becomes even more enjoyable and our summer migrants begin to arrive. Among these are numerous warblers that have been sunning themselves in warmer climes. The first of our thirteen or so migrant warblers to arrive is generally the chiffchaff but, climate change is beginning to alter their habits and a few now tough it out through the winter here in Britain instead of flying south. The blackcap also provides a ‘good news’ story of how, for a change, we are helping nature to increase her bounty rather than destroying it by providing what the RSPB refers to as ‘a viable option’ for this particular warbler.
Through April, the beautiful notes of the male blackcap will be serenading us from hedgerow and thicket, and he is sometimes referred to as the ‘northern nightingale’ on account of his exquisite and musical song. The bird is named after the male who has a jet-black crown while the female sports a chestnut brown crown.
Although summer visitors, blackcaps are now wintering in Britain with increasing frequency. However, these birds are not our summer visitors extending their stay indefinitely, as most of our breeding blackcaps migrate south to Spain and North Africa. Until very recently it was though that our wintering birds came exclusively from southern Germany, but further research indicates that they migrate from breeding areas across the whole of Europe, including Spain! So, while it appears that most blackcaps fly south, where, despite the law, they may be hunted or trapped by humans, here, the milk of human kindness towards our feathered friends runs deep, and they find increasingly plentiful supplies of bird food put out in our gardens.
Climate change, of course, has a big role to play in this story and although East Anglia tends to be colder than the southwest of England where most of our overwintering blackcaps can be found, a few are now spending the winters here too. They may find some of our winter days decidedly chilly, but so long as they have access to a constant supply of food they can survive because they do not have to expend large amounts of energy in looking for their next meal. Overwintering Spanish birds eat mainly fruit and berries and must keep on the move whereas our birds tend to be sedentary and seed eating, relying on predictable supplies from our garden feeders.
Interestingly, research appears to confirm that British birds have the edge when it comes to breeding because in the spring, they migrate earlier than their North African or Southern Spanish counterparts. This is because, as the days lengthen, critical day length is achieved around ten days earlier in Britain than around the Mediterranean. Our wintering birds, therefore, leave earlier and have the pick of the best continental habitats which, in turn, may lead to greater breeding success and an increased number of chicks. This should mean that greater numbers of blackcaps will be wintering in Britain in the future and if the trend continues, eventually they will be classified as a distinct subspecies. They already show some variation in that they have longer and narrower beaks, presumably an adaptation for eating more seeds, as well as rounder wingtips.
Adrian Walters, Honorary Freeman of Sudbury and Clerk to the Trustees of the Sudbury Common Lands Charity