Following the "Canary Wharf Migrant Watch" survey, I decided to reconnoitre another iconic City building: St Paul's Cathedral, which has long been a historic landmark. Close to the Thames and with its magisterial dome dominating the skyline, people come from all points of the compass to admire Sir Christopher Wren's 336-foot Portland stone masterpiece. Although now eclipsed by newer high-rise buildings, its character remains unrivalled. St Paul's also happens to be the centre of the LNHS (London Natural History Society's) 20-mile-radius recording area. Thus, having previously monitored Canary Wharf in 2000–2008 with a degree of success, I decided to cover this possible obstacle to migration and its accompanying small churchyard gardens, as they might just hold the odd migrant bird.
St Paul's Cathedral (Ken Murray).
Between 15th April and 4th May 2012, I monitored the small churchyard gardens on twelve days; this returned, on an relative abundance basis, 26 (migrant) bird days. My sightings included five species of warbler: Reed Warbler, Willow Warbler, Blackcap, Chiffchaff, and Common Whitethroat (the last singing on two occasions!).
Common Whitethroat, St Paul's Cathedral, London (Ken Murray).
Low pressure dominated the monitoring period, which may have contributed to the unexpectedly high occurrence of migrant warblers. However, what was surprising from this mini-survey was that on one visit (multiple sightings), five migrants were found within 10m × 10m of relatively sparse shrub cover. I believe this support the idea that migrants moving in a front over a sterile urban area drop into small islands of cover for refuelling purposes before travelling on to distant preferred breeding and/or wintering grounds.
Reed Warbler, St Paul's Cathedral, London (Ken Murray).
At first glance these areas of cover within the City's towering developments sometimes appear too small or too disturbed to warrant attention; however, my experience has suggested that if the cover holds invertebrate life then, with perseverance and luck, migrants can be found.