Chapter 15: With this ring

Finding or catching Aquatics all comes down to the weather. Ian Lewis illustrated the point in the 1995 bird report. “In the early part of August an area of low pressure remained North of Britain producing a north westerly air flow. Then on the 6^th high pressure with weak easterlies settled over the south and three birds were trapped the following day. From the 7^th to the 22^nd the wind remained mainly in the east and a further nine birds were trapped. On the 13^th a front lay over southern England with a low to the north and a high pressure to the south. Any birds migrating from the continent encountering these conditions would probably make landfall as indicated by the four Aquatics trapped on the next morning” (Ian Lewis in Ashby 1995).

At that time we knew these warblers were breeding in Poland, Belarus and Hungary, but the wintering grounds were a mystery. An Aquatic Warbler had been trapped by ringers in Djoudj National Park in northwestern Senegal on 8 February 1993, but it wasn’t until 2007 that a Birdlife International team confirmed that this was one of their most important wintering grounds. The way they did it was very clever. They got ringers to collect feathers from adult birds caught in Poole and other European ringing stations, knowing that certain feathers would have been grown on the African wintering grounds. They compared the patterns of the feathers’ isotopes with the patterns on isotope maps of West Africa and found what looked like a perfect match in Djoudj. Sending in a team, they estimated that a third of the world’s population was wintering in the park, in an area of just 100 km² (van den Berg 1993, 2007; BirdLife News February 2007).

Ringing stations are powered by sound. At Keysworth, the private estate on the northern banks of the River Piddle, the Stour Ringing Group used to broadcast birds songs to the skies during consecutive autumns from 1991 to 2000. Grasshopper, Reed, Sedge and Aquatic Warblers were all played from a multitude of tape machines. This effort bagged them some impressive totals, including 82 Aquatics, most of which were caught in the first seven years.

The Stour Ringing Group is organised by amateurs, each of whom used to take their annual holiday to man the station at Keysworth or got up at dawn to fit ringing in before work. When Aquatics became rarer, their enthusiasm started to wane. Then the Keysworth estate changed hands to a less sympathetic owner and the ringing station had to be closed. Shaun wanted to set up a station in Lytchett Bay. Having the necessary permissions to tape lure, he set up a tape to start 45 minutes before dawn on chosen mornings. Bob Gifford provides the tapes for the Stour Ringing Group and has made and installed the broadcasting equipment.

The sounds on a ringer’s tapes are selected with all the attention a chap might employ when choosing music for a lover. Made on dark winter evenings, they lay bare the hopes and dreams of the maker. So, for example, along with the warbler species that are the staple catches in a reed bed, in goes a bit of Pallas’s Grasshopper Warbler, Bluethroat and Scarlet Rosefinch, and this is topped off with a good strong helping of Aquatic Warbler. For the ringers among our readers, Magnus and I made our own version. Each sound has been chosen to best create the feeling of a party going on (CD2-36). 

Aquatic Warbler song is fairly repetitive, so after a few mornings of passive listening while the nets are being checked and the birds ringed, you become familiar with it. At 08:30 on 16 August 2005, Bob and Shaun were packing up to leave the ringing site, and knowing that they weren’t coming back the next day, Bob disconnected the battery from the timer and speakers. As they left, a familiar song started from the reeds. Nothing registered for about 30 seconds. Then absent-mindedly, Shaun shouted to Bob to disconnect the Aquatic tape. “I have”, shouted Bob. “It’s coming from the other side of the reed bed.” An Aquatic Warbler singing? Shaun couldn’t believe it. They rushed over to the reed bed and scanned, but there was no sign, and frustratingly the bird had gone silent.

He came to the conclusion that it had to be me hidden in the reeds playing the song to trick him. He still suspects that, although he has put Aquatic Warbler on his Lytchett list. I promised to come clean in this book.

I find it just as hard predicting a whole series of other warblers in Poole Harbour. Take Wood Warbler, which is always difficult to pin down in the spring, the only time of year when we have a real chance of finding it. There’s a small wood between the Arne road and The Moors that has sprung up around the high, moss-covered banks of a Saxon ruin. Sometimes in spring, less often nowadays, a male Wood Warbler will stop by to sing there for a few days. At one time they bred in Slepe Copse, and over the years I’ve heard several sing on the wooded slopes of Nine Barrow Down.

Recent research has shown that the number of Wood Warblers in a particular wood is correlated with fluctuations in the size of rodent populations, rather than the availability of food. Apparently, returning males can quickly sense whether the woodland has a high mouse population and, if it has, they move on to inspect other woods until they find a suitable one to start singing and attracting females. Since Wood Warblers nest on the ground, their eggs could be eaten, not only by mice but also by their predators. It must have been a bad mouse year in 1988, because three pairs stayed on to breed.

The six most common breeding warblers in Poole Harbour include three summer visitors – Reed Warbler, Common Whitethroat (CD2-37) and Willow Warbler (CD2-38) – as well as Dartford Warbler, Blackcap and Chiffchaff (CD2-39), which can be found all year round. Poole is unusual in that many of its warblers overwinter. Cetti’s Warbler (CD2-40), Blackcaps and Chiffchaffs all started wintering in Poole, surprisingly during the colder ‘70s, and recent warmer winters have helped them expand their range. In the case of Cetti’s, they are thought to have arrived here by way of Kent. 

Poole Harbour has a third of Dorset’s Cetti’s Warblers, and 6% of the British population. There are around 30 singing males from the Corfe River valley round to Lytchett (which has 11 pairs), and Hatch Pond where there are three singing males.

A wintering Yellow-browed Warbler was found just around the corner from Sainsbury’s by Jill Bale, one of our more persistent lady birders. It spent its time in the back gardens and scrubby edge along the west side of Poole Park. My dentist’s practice overlooks a neat shrub-bordered garden there, and I’m proud to say that while having a tooth capped I managed to squint through the goggles, past the drill and beyond the reflection of two white coats, to get a glimpse of the Yellow-browed feeding in his garden.

Yellow-browed Warblers are best found by call. There have been more than 10 now in autumn, and another one wintered in 2003/04 in the bushes along the edge of Border Drive at Lytchett. If you would like to find one of the ‘autumn’ warblers like Pallas’s Leaf Warbler or Yellow-browed Warbler you have a difficult choice. I found the first Pallas’s for the harbour while birding on the end of Pilot’s Point with my daughter Claire (then aged 9) on 25 October 1999. She still remembers it fondly. I was teaching her to make the Stonechat’s tongue-clicking call, and as she did it a Pallas’s flew up on to a piece of gorse next to us, had a look, and dived into cover. Nick found another rather obliging bird at the start of the path to Old Harry in 2007 after trying to relocate a Yellow-browed he had found half an hour earlier. The same rather, shall we say, sensitive site has now hosted quite a few Yellow-browed.

So, to find these you have a choice: visit the dentist, hang around on the edge of a nudist colony with a child, or spend the day with binoculars looking in a tree directly above the ladies’ toilets in Studland village, on the way to Old Harry. 

The final sound in this chapter is a biological curiosity. It’s a song made by a Firecrest but it sounds a bit like a Goldcrest (CD2-41). Firecrests arrive here in the autumn and often overwinter. In 2012 a pair built a lovely nest on Brownsea near the heronry. Because they are not regular breeders a young male that stays on to attempt breeding will have no other males to sing against. This encourages a phenomenon known as mixed singing where the stranger picks up phrases of its closest relative. Some times over a period of three years the mixed singer may adopt the complete song of the more common species, in this case Goldcrest. These birds aren’t hybrids, rather they are confused. There is another bird that turns up in Poole that gets everyone confused. Siberian Chiffchaff.

>>> Chapter 16: Drab >>>