The Great White Egret was still on the Slurry Lagoon this morning. A light passage of Swallows was noticed and some Sand Martins were near the railway bridge. These were attacked by a Hobby, which appeared to have caught something. Later the same or another Hobby was seen, again attacking the Sand Martins, over the Deep Pit. PS.
This morning, during the Warbler Walk, nine warblers were seen or heard (just Grasshopper Warbler missing). A Hobby attacked the Swallows at the Railway Bridge, but they saw it coming. The Slurry Lagoon Mute Swans now have eight cygnets and there are several Coot families and the Great Crested Grebes on the Slurry Lagoon still have their chick. Earlier on, at about 08.00hrs a Cuckoo was singing from an ash tree beside the railway line. PS.
This morning there were two Grasshopper Warblers near the Large Gravel Pit. Two Garden Warblers were singing, the best one near the railway end of the Causeway. A pair of Shelduck spent some time on the Slurry Lagoon and two House Martins were seen near the Railway Bridge. PS.
This morning a Willow Warbler was singing in the Boundary Hedge. JDn.
In the afternoon a Swallow was by the Railway Bridge with eleven Sand Martins and two Wheatears were on the Severn/Trent fields. RW.
This afternoon a female/juvenile Redstart was seen beside the Slurry Lagoon, near the access gate, and a Hobby was harassing the Swallows near the railway bridge. SC, PG.
As I walked towards the river by the railway bridge I heard a deep croak so looked all around to see if I could see a Raven. There were about 250 Carrion Crows on the field across the river but no sign of a Raven. Then I heard another rattling croak and two Ravens flew from behind me, over the signal box and out over the river. One was in pursuit of the other and both held their bills open with their exertions. They flew right overhead giving good views of their tails and towards the pylon, where they started to gain height. Some of the Carrion Crows took exception and joined in the chase, calling loudly and there was a melee of black wings as they dashed at each other. Soon the two Ravens broke away, still intent on their own dispute, and then they locked feet and cartwheeled towards the ground. At the last moment they disengaged and landed on the ground, taking off again immediately before flying back across the river, over my head again and back the way they came, towards Colwick. PS.
This morning in the bushes by the railway bridge a large flock of warblers and finches was feeding. Amongst them were two Spotted Flycatchers, one being chased vigorously by a juvenile Chiffchaff. There were also three more Chiffchaffs, two Lesser Whitethroats, five Whitethroats, two Blackcaps, two Willow Warblers and two Reed Warblers. The finches were family parties of Greenfinches, Chaffinches, Linnets and Goldfinches. Two Yellow Wagtails were with finches and warblers along the Boundary Hedge and another Yellow Wagtail flew over the Causeway. At about midday a Hobby attacked the Swallows by the Railway Bridge, but was unsuccessful although it was seen to stoop several times. PS.
Although beautifully sunny there was still a cold north wind blowing so not much migration was noted. A Swallow investigated the nest sites under the railway bridge, so it might be the first one of our birds back. Several Sand Martins flew through and there was a northward passage of Skylarks. Six Common Terns were on the Deep Pit and two Sedge Warblers were singing. On the dry end of the Slurry Lagoon were a very smart pair of Wheatears. PS.
A Whinchat and a Wheatear were seen this morning, both on the Deep Pit fence by the Railway Bridge, though not at the same time. Two Hobbies were also seen here. About six Brown Argus were seen around the site and more Long-winged Coneheads, as well as several Migrant Hawkers, Brown Hawkers and a Southern Hawker. The Lower Path had a flock of warblers, containing Garden Warbler, Blackcap, Whitethroat and Lesser Whitethroat, Willow Warbler and Chiffchaff, plus two Willow Tits.
Ten People turned up at the main gate at 20.15 to see what bats could be found over the lagoon site. Rebecca Tarry, senior ecologist with SLR Consulting, led the survey and distributed bat boxes to those who did not have them. Bat boxes translate the calls of bats, inaudible to humans, to a sound within the range of human hearing. Some of the boxes were set to different frequencies so that as broad a range of bats as possible could be detected. Rebecca explained to us how the different bats sounded and how some use harmonics, so that the lower harmonic of one bat’s call and the higher harmonic of another could both be picked up with the bat box tuned to one frequency.
We walked along the top of the Slurry Lagoon bank, towards the river but, as the bats frequently wait until about twenty minutes after sunset to start feeding, we did not pick up any calls. At the corner of the Deep Pit, by the river, Rebecca placed an Anabat box to scan the Deep Pit water surface below. This device records the bat calls in bursts of a few seconds so that they can be analysed later on a computer with a programme that produces sonograms. Each bat’s sonogram is unique to its species, except for a very few Myotis species which are very difficult to separate. We left the box where it was and continued around the top of the Deep Pit. As we walked along two Common Sandpipers, which had been calling on the river, flew past us and on the Deep Pit the Tern platforms, which we thought had been deserted since the Terns finished breeding, were being occupied by roosting Terns.
We carried on around the Deep Pit and then past the Slurry Lagoon, where the Starling roost could be heard as its occupants quarrelled over perches in the deepening gloom. In the background the calls of gulls and geese could be heard as large flocks of them were also coming in to roost. We arrived near the footbridge, with still not a whisper from any bat although there were plenty of insects about, when someone suggested standing on the bridge for a while as they had seen Pipistrelles here in the past. Soon a Pipistrelle was heard giving its peculiarly ‘wet’ sounding clicks, and then another call identified as a Noctule. Another bat was then seen flying silently in the half light between two hedges. Rebecca explained that bats in fact have very good eye-sight and, where they know there is an open space, they do not need to echo-locate, in fact there is nothing there to catch an echo from. Pipistrelles fly in a very erratic way, with lots of twists and turns and often forage on insects attracted to lights. They are very small bats, their body being no bigger than the top joint of your thumb, but they need several thousand gnats or midges a night to keep them in good condition. There are two species of Pipistrelle which were only separated when bat boxes were invented. One calls at a frequency of 45 and the other at 55, called the Soprano Pipistrelle. People then realised that the bats calling at these frequencies formed discreet populations and were in fact two different species. Noctules are much larger bats and can be seen flying at dusk (or even in the middle of the day), sometimes mingling with Swifts as they make aerobatic stoops to catch large flying insects like cockchaffers or large moths.
Willow Walk promised to give some good bat foraging opportunities so we walked along its length but only picked up two more Pipistrelles before we were back by the gates. We now walked along the Lower Path, back towards the river, getting more Pipistrelles and a Noctule flying over. At the Railway Bridge the bat boxes started to pick up a new sound, much ‘drier’ than the Pipistrelles, and Daubenton’s Bat was identified. Rebecca switched on a very powerful torch and the Daubenton’s were seen flying through its beam very low over the water. She told us that Daubies use their feet and tails to catch insects close to or on the water’s surface. The torch beam was thick with flying insects, so there was abundant food for bats, but there were not many bats around. Rebecca then saw another bat in the beam that didn’t behave quite as the Daubenton’s were and provisionally identified it as a Natterer’s Bat. More Pipistrelles, including Soprano Pipistrelles, and Noctules were also found here so the river was definitely the most productive site for bats so far.
We didn’t expect to get a great deal more now so we went back up the Deep Pit bank to retrieve the Anabat box. The bat boxes could detect Pipistrelles and Daubenton’s over the water and these were soon picked out in the beam of the torch. Having retrieved the Anabat box we made our way along the top of the bank towards the gates. Bat activity faded as we got further from the river and we picked up none once we were walking by the Slurry Lagoon. This brought us to the end of our survey so we returned to our cars, Rebecca saying she would analyse the recordings she had made and let us know the results.