Scream of the Swift
Scream of the Swift
Blog Category: General update
The scream of the Swift Apus apus can finally be heard swooping over the Cradley site as they return to the UK to breed. Our temperate summers and abundance of food in the form of insects on the wing, is what makes the UK a wonderful place for this aerial acrobat to rear its young. Swifts are amazing in that they do not land other than to breed, and it was not until Edward Jenner (a great scientist who invented vaccination) studied them, that we discovered that the same individuals were returning to the same nest sites year on year.
Following this discovery, Edward also noted that when the Swifts he was studying returned to the nest, they were very plump and in good plumage. Edward hypothesised that they were migrating and not hibernating. Prior to this, scientists thought that they over-wintered in ponds, buried below the mud. Some records even account for people draining ponds or pools and digging through the mud to try and find them. It seems remarkable to think this now, as the migration of the Swift is now well understood. But again, it was not until a French pilot in the first world war came across motionless birds at 10,000 feet, that the question of “Where do Swifts sleep?” was answered. It was then discovered that Swifts only rest one side of the brain at a time, so that they can keep an eye on what is going on†.
Having Swifts fill our skies over Cradley is fantastic, because like many species they are in chronic decline. Their decline is attributed to a number of factors including but not limited to, habitat loss, nest site loss and availability of food. But how are they are intrinsically linked to the River Stour and the surrounding lands of its catchment? They are linked through the exact points which are affecting their population decline; an abundance of insects to feed on; nesting sites which are plentiful in old properties; and the River Stour which is a rich wildlife corridor.
As we delve below the surface of the River Stour, it is easy to think no life is to be found, but there is an abundance of life. Many of the species that do live below the surface of the water, are the larval stages of flying insects. Not only do they offer a bounty of food to the fish that live in the river but when they emerge to mate, they also become the food of the aforementioned Swifts among many other things.
There are many species of invertebrates you can find when studying rivers, and the make up of what species are found within the river is a great indicator to its health. We can even use the presence of a species in one part and not in another part, as a signpost to possible issues. If you regularly survey a stretch of river, and all of a sudden many of the species disappear from your sampling, you know something has happened. This can be really useful for identifying pollution incidence or misconnections.
The requirements of specific species can indicate how oxygenated the water is, the chemistry and how stable the parameters are. The Greggs foundation and the vital funding they have provided to the Severn Rivers Trust and this project, allow us to offer you a safe environment to do just that. With volunteering starting back up and larger groups allowed, we can start the process of getting into the river and surveying what lies beneath the surface. #Greggs4Good
Have you ever walked down the banks of the River Stour and wanted to know what wildlife you are looking at? Why not come down to one of our events and join in, learn and meet new people.
Some of you may follow the Facebook group https://www.facebook.com/groups/riverstour/ and you may have spotted a post the other day showing a Pipistrel bat Pipistrellus Sp. flying in broad daylight in the clearing between the two banksides of the river. This bat would have been taking full advantage of the clouds of insect life that where emerging from the river, and needed a break in the rain to get out and feed, taking on the risk of predation in broad daylight for the opportunity to feed.
Another member of the group has posted a fabulous video of a large Chub Squalius cephalus seen beneath the water tucked into the bank. It is a common behaviour of Chub to tuck into the edges or find cover under interesting features in the river like tree roots or overhanging vegetation. This individual was estimated to be around 1.8kg (4lbs) or close to two bags of sugar. The Chub can live up to 20 years so this individual may still be lurking around the banks when you next walk down to the river.
Within the gallery of pictures as promised is a map of the site.
Until next time,
Your Urban Rivers Officer Tom.