A total of 61 species were seen this year beating the previous high of 54 in 2019.
Five species were added to the Warren list; Stackelberg’s Ant-hill Hoverfly Xanthogramma stackelbergi found on 6 July and Yellow-girdled Fleckwing Dasysyrphus tricinctus on 25 August were unexpected additions. The former was added to the British list as recently as 2012 with only a few recorded occurrences so far, whilst the Fleckwing is normally associated with coniferous woodland and heathland.
The three other new species were not unusual in their occurrence but did increase the overall Warren hoverfly list to 77 species. On 7 May, Blotch-winged Hoverfly Leucozona lucorum and Big-thighed Pipiza Pipiza austriaca and on 30 August Bronzy Marsh Hoverfly Riponnensia splendens.
The first hoverflies to make an appearance were fresh out of hibernation, with Common Dronefly Eristalis tenax and Marmalade Hoverfly Episyrphus balteatus on 28 February. Other early spring hoverflies included Common-spotted Field Syrph Eupeodes luniger, Dull-bellied Blacklet Cheilosia proxima, Hairy-eyed Syrphus S.torvus, Humming Syrphus S.ribesii, Slender Melanostoma M. scalare, Spotted Meliscaeva M.auricollis, Spring Epistrophe E.eligans and Tapered Dronefly Eristalis pertinax.
There were large increases of both species and numbers as temperature rose and more flowers came into bloom, by the end of May a total of 28 species had been seen. Noteworthy amongst these were Broad-barred Fleckwing Dasysyrphus venustus, Buff-tailed Bear Hoverfly Croirhina floccosa and Smudge-winged Clubtail Neoascia podagrica.
A hot and sunny spell of weather at the beginning of June saw many migrant species arriving with thousands of Marmalade Hoverfly, hundreds of Common Twist-tail Sphaerophoria scripta and dozens of White-clubbed Glasswing Scaeva pyrastri and Common-spotted Field Syrph across the site.
Flowering umbellifers in June and July attracted Batman Hoverfly Myathropa florea, Bolete Blacklet Cheilosia scutellata, Bumblebee Blacklet C.illustrata, Common Pipiza P.noctiluca, Compost Hoverfly Syritta pipiens, Dark-winged Chrysogaster C.solstitialis and Pied Plumehorn Volucella pellucens.
Other hoverflies like Bumblebee Plumehorn Volucella bombylans, Common Paragus P.haemorrhous, Hook-banded Spearhorn Chrysotoxum festivum, Hornet Plumehorn V.zonaria, Striped-backed Fleckwing Dasysyrphus altostratus, Stripe-faced Dronefly Eristalis nemorum, Stripe-winged Dronefly E.horticola and Two-banded Spearhorn C.bicinctum preferred to nectar on buttercups, dandelions and bramble. At peak times in summer over 20 species can easily be found on site.
August produced further additions to the annual tally with Broad-banded Epistrophe E.grossulariae, Furry Dronefly Eristalis intricaria, Golden-tailed Leafwalker Xylota sylvarum, Small Spotty-eyed Dronefly Eristalinus sepulchralis, Large Tiger Hoverfly Helophilus trivittatus, Matt-backed Melangyna M.labiatarum and Wasp Plumehorn Volucella inanis.
By early September Glass-winged Syrphus S.vitripennis, Parsley Blacklet Cheilosia pagana and Short Melanostoma M.mellinum were added and migration continued and Common Dronefly, Humming Syrphus and Tiger Hoverfly Helophilus pendulus appeared in increasing numbers nectaring on the plentiful Water Mint and Common Fleabane. A Yellow-barred Peat Hoverfly Sericomyia silentis on 24 September continued the recent run of autumn occurrences for this upland and heathland species.
Above average temperature and sunny weather encouraged a good range of hoverflies to remain active well into October with eight species still on the wing on the 21st. Although numbers were dropping rapidly in November, on sunny days hoverflies could still be found in ones and twos with no less than seven species on 18th including Hairy-eyed Syrphus, Humming Syrphus, Marmalade Hoverfly, Slender Melanostoma, Spotted Meliscaeva and Tiger Hoverfly and an exceptionally late Gossamer Hoverfly Baccha elongata. Sightings continued into December with Common Dronefly, Common-spotted Field Syrph and Marmalade Hoverfly on flowering Gorse.