On 31st August 2018, Steve Garland collected a solitary bee at North Walney NNR, Cumbria that he identified as Colletes halophilus (Sea Aster Colletes). This was an extraordinary find, as most of the world population of this species is thought to be restricted to saltmarshes in the south and south-east of England, from Chichester Harbour to Spurn Point, where it is strongly associated with Sea Aster (Tripolium pannonicum) for nectar and pollen.
Moving forward to August 2020, Tim Rogers photographed an apparent nesting aggregation of Colletes bees on the edge of the Shrimper’s Track at Marshside, on the Ribble Estuary, north Merseyside (Fig. 1). This 1.3km hardcore track across the intertidal zone was created in the 1970s for extraction of sand by heavy machinery. His photos showed bees similar to C. halophilus but specimens to confirm the identity were not taken. On 26th August the following year, Pete Kinsella and Mark Nightingale photographed Colletes bees on dandelions (Taraxacum agg.) and Sea Aster at Marshside but, again, no voucher specimen was obtained. I organised a small expedition to Marshside on 8th September 2021 to search for the bee but we did not find any.
Determined to try again, Trevor Davenport and I visited Marshside on 28th August 2022 and, after searching a large area of Sea Aster without success, we came across a large number of typical Colletes burrows, extending for about 65m along the edge of a low ridge on the south side of the Shrimper’s Track (Fig. 2). Having obtained permission, Trevor managed to pot two female bees at their burrows (Fig. 3). These were sent to Ben Hargreaves; he passed them on to Steven Falk who confirmed C. halophilus and requested further specimens. We collected two more females on 6th September 2022; these were also confirmed as C. halophilus by Steven.
In the meantime, a much earlier record of putative C. halophilus on the Ribble came to light, in the form of a photograph of an aggregation of Colletes bees on the Marshside Shrimper’s Track taken by Steve McWilliam on 14th August 2016. It was posted on iNaturalist but had been overlooked. It is likely, therefore, that C. halophilus has been in the region for at least six years. It is also more widespread than originally thought, a colony of putative C. halophilus being found at Heswall on the Dee Estuary in September 2021. Further observations in August 2022, including the finding of a possible nest site, led to voucher specimens being collected and confirmed as C. halophilus by Steven Falk. In September 2022, similar bees were discovered utilising Sea Aster on a ‘Green Beach’ at Hoylake, north Wirral. As the population was deemed to be small, no specimens were collected for confirmation.
This scarce bee has made an extraordinary leap across England to the north-west coast. Further investigations are justified to determine the extent of its distribution, including around Morecambe Bay, the north Ribble and the North Wales coast.
I am grateful to the following for correspondence: Chloe Aldridge, Leanna Dixon, Steven Falk, Andrew Goodwin, Ben Hargreaves, Gary Hedges, Pete Kinsella, Alex Piggott, Tim Rogers, Joshua Styles and Jane Turner. Tim Rogers kindly allowed me to use a photo of his Marshside bees. Alex Piggott gave permission for specimens to be collected in the RSPB Marshside Nature Reserve. Trevor Davenport helped with the search at Marshside and, with some skill, potted the voucher specimens. Ben Hargreaves and Steven Falk used their expertise to identify specimens.