Wednesday, 30 September 2020

Hull Dragons 2020: September summary

Autumn is definitely on the air, after the warm and sunny days that have brought the dragonflies and damselflies out in the first three weeks of the month, cooler weather with northerly winds and more rain set in for the last part of the month. A total of 133 records from 8 species were submitted in September by 15 observers, covering 31 km2. Thank you all for your efforts. The survey is set to surpass the number of records submitted last year, with a total so far of 696 records. 

March of the Willow Emerald
The Willow Emerald Damselfly has expanded through the UK since 2009, after natural colonisation from Europe. A year ago Dick Shillaker found a male Willow Emerald at East Park, the first record for East Yorkshire. This year, we've had a number of records for the species in the Hull area, in fact, it has been the 3rd species in number of records for September after Migrant Hawker and Common Darter. A warm, breezy afternoon - one year to the day of the first record - I bumped into a mating pair, first flying and then settled on a buddleia branch, just under the pedestrian bridge at Abbey Way, over the Beverley & Barmston drain (top shot). Some distance away, a lone female basked on a Japanese Knotweed. A few days later, we had another set of records at a new location, Humber Bridge Country Park, where 6-7 individuals with two mating pairs in the same area and records for a number of days. A male was spotted at the Beverley and Barmston Drain by Beresford Avenue. The sudden increase in records from last year and their spread, and the number of individuals involved may suggest that the species may have been overlooked last year, when it might already have bred in Hull. Alternatively, there has been a massive influx of individuals arriving at suitable sites coinciding with the warm weather and southernly winds?
Female Willow Emerald Damselfly on Japanese Knotweed.

Beverley and Barmston Drain
I have been visiting the Beverley and Barmston drain regularly this year. It has been surprisingly good for dragonflies, with even a Hairy Dragonfly early in the year. The drain does looks like ideal habitat for Willow Emeralds: very slow flowing and with occasional willows over the water. 
A terrapin emerges from the blanket of duckweed
Moorhen sat on floating rocking horse.
A stretch of drain with overhanging willows.
This stretch of the drain has large trees on one side.

Abbey Way pedestrian bridge.
Beresford Avenue bridge.
Breeding Migrant Hawkers
September is peak breeding season for Migrant Hawkers. They reach maturity and males develop intense blue and yellow colours. Females also have more rich brown and yellow colours. Individuals may still be seen away from water, but as they mature, they are increasingly found by their breeding lakes and ponds where their behaviour becomes more focused on breeding. Males patrol areas by marginal vegetation, often hovering over this for some seconds before moving to prospect another area. Sometimes they enter marginal vegetation searching for females. If a female is spotted, mating ensues. I have been able to follow two mating pairs from the beginning. The pair flies away from the water and settles on trees or marginal vegetation, on a south facing spot. Although I've watched many pairs mating, in two instances I could watch a mating pair for a long time, since the initial capture of the female by the male. These two pairs remained mating for over 32 minutes and over 17 minutes (I didn't stay the full length of the mating so these will be underestimates). I have been unable to find any information on the average mating length in the species. In a previous post I have covered the mating system in this species, which concludes that non-territorial species, like the Migrant Hawker, where sperm competition is likely to be more intense, mate for longer, and is nice to see that my observations match this expectation.
A resting male in full breeding colours.
Mating pair at Noddle Hill lake.
Migrant Hawker ovipositing on floating branch at Foredyke Green Pond, an unusual ovipositing spot for this species.
Female Migrant Hawker ovipositing on branched burr-weed leaves, by the water. 
Brown Hawker ovipositing on floating wooden board.

Species recorded in September

Migrant Hawker, 74 records.

Common Darter, 30 records.

Willow Emerald Damselfly, 11 records.

Southern Hawker, 6 records.

Small Red-eyed Damselfly, 2 records.

Blue-tailed Damselfly, 1 record.

Ruddy Darter, 1 record.

Brown Hawker, 1 record.

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