Friday, 4 October 2019

Hull Dragons: September summary

I didn't think I would write a September summary for Hull Dragons. However, the first three weeks of September were generally dry, sunny and warm - though breezy at times - allowing for plentiful dragonfly surveys. In contrast, the end of the month was very overcast, wet and the temperatures plummeted. Overall, 134 records were submitted to iRecord from 9 species in September by 4 observers. Although fewer species have been active in September compared to August (9 compared to 13), and the general diversity is lower, the spread of the records is increased, with the records coming from 30 km2. 83% of the records were for Common Darter and Migrant Hawker. There were 8 Southern Hawker records and 5 Ruddy Darter records, the remaining species having one or two records each in the month. Most notably, however, a male Willow Emerald was first recorded at East Park. This is not only a great addition to the Hull Dragons survey, but it is the first record for all of East Yorkshire (see my previous post about it here).

With the addition of these records and the dragonfly records submitted through Birdtrack, HullDragons has now accumulated over 500 records, which are far more than I would have anticipated at the start of the survey.

Other than my Willow Emerald twitch, my favourite dragonfly trip this month was at Noddle Hill. The sheltered 'Snake Pass' ride is a favourite haunt of Migrant and Southern Hawker, hunting and sunbathing and both Common and Ruddy darters also favour it. The NW corner of the lake, with a wide belt of marginal vegetation, in a sunny, sheltered corner, had plenty of Migrant Hawker activity, with several mating pairs, two of them sitting close to each other. A male Ruddy Darter was also on territory. The following are some photos of that survey on the 18th of September.
Female Migrant Hawker.
Male Southern Hawker.
Mating Migrant Hawkers.
Mating Common Darter.
The patrolling Migrant Hawker males over the water offered some opportunities for in flight photography.
Male Ruddy Darter on territory.

 List of species recorded on September

  1. Southern Hawker
  2. Brown Hawker
  3. Migrant Hawker
  4. Ruddy darter
  5. Common Darter
  6. Small Red-eyed damselfly
  8. Black-tailed skimmer
  9. Common blue damselfly
Note: this will be the last monthly summary for HullDragons this year

Tuesday, 10 September 2019

Willow Emerald twitch at East Park

When I posted the Hull Dragons August summary on the 6th of September, I noted that, regarding the Willow Emerald Damselfly "there is a possibility this rapidly expanding species may make it into Hull in the near future". But I was never expecting the near future to be as quick as 48 hours! @pondwatcher on Twitter:

How exciting was that!?
The Willow Emerald benefits from urbanisation, as it favours permanent garden and park ponds, surrounded by trees or bushes. Its is a late flying species, making the end of the dragonfly/damselfly season more exciting. It is the only Odonata species that oviposits into live wood, usually thin branches overhanging water, where eggs induce a diagnostic, gall-like reaction in the wood in a pattern of parallel lines.
 After a few sporadic records, the Willow Emerald became a regular breeding species in the UK in 2009, where many breeding colonies were discovered in Suffolk. Since then, it has steadily increased in range west and north, and this year it crossed the Humber for the first time.
 Today, there was a forecast of sunny spells and light WNW wind, and I decided to got on a damselfly twitch. I arrived at the park at 9:00 and walked to the eastern side of the lake, where the area around the boardwalk is favoured by dragonflies and damselflies. The first sunny spell took about an hour to arrive. When it did, Migrant Hawker males became active, with up to 5 males sharing the area, patrolling and resting over the large patch of marginal vegetation (above), a single female making a short appearance.
A female Common Darter (above) sat on the railings of the boardwalk, the first record of this species in the park this year. After walking up and down for a while searching for the Willow Emerald and with another large cloud looming, I moved onto the western side of the park to search for Small Red-eyed Damselflies. No luck, not a single damselfly on the west side of the main lake or boating lake.
 After a hot drink in the cafe I returned to the boardwalk. More searching of trees and marginal vegetation and walking up and down the boardwalk. The Migrant Hawkers were active so I watched them for a while. It was 12:20, the temperature quite pleasant in the sun, barely a breeze. Two male Common Darters were in attendance, chasing. After three hours in the park, I thought I had to content myself with a tandem pair of Common Darters, which were looking for an oviposition site. Maybe the Willow Emerald had succumbed to predation, of moved on. Another cloud was coming. I thought I'd stay for the next sunny spell. Then, a lovely, large sturdy green damselfly flitted about, checked the passing pair of hesitant darters in tandem, and sat on a leaf near the boardwalk: yes! the male Willow Emerald! It gave the impression of a sizeable insect, it is indeed as long or a bit longer than a common darter, and a stronger flyer than the common emerald. It sat on exposed leaves over the water, moving every now and then to another perch. It sat on alder leaves, on branched burr reed flower heads and leaves. I could take plenty of photos, as I watched it for about 20 min. A lovely damselfly tick!
This photo shows the 'spur' on the side of the thorax and the pale pterostigma with dark edges.
The pale appendages are also distinctive. No bluish pruinescence is apparent.

Willow Emerald males often sit on low branches of trees, overhanging water, which are the ovipositing sites chosen by females.

Friday, 6 September 2019

Hull Dragons: August summary

The dragonfly season has been in full swing, particularly during the very warm Bank Holiday weekend. Thirteen species and a total of 130 records from 23 km squares have been submitted so far to iRecord during August. Seven recorders have contributed to these records. During the last part of the month a number of species were still on the wing, although the records were dominated by Common Darters and Migrant Hawkers, two late, abundant and obvious species that also roam away from water. Both species add squares to the survey that don't necessarily hold breeding sites.
  Choosing highlights hasn't been easy, but these are some.
 Small Red-eyed Damselfly
To the thriving population at East Park we added Pickering park as a new site for the species, where many individuals and ovipositing was confirmed. A few other scattered records are evidence of the rapid range expansion of this species.
Migrant Hawker
A great year for Migrant Hawkers. They have been plentiful, with almost 50 records submitted to iRecord to 6th of September, compared to 18 last year. More excitingly, breeding evidence was obtained, with multiple patrolling males on several potential breeding sites with mating pairs at Pickering Park, Foredyke Stream, Beverley and Barmston Drain, and oviposition observed at Foredyke Stream.
Southern Hawker
A total of 22 records have been submitted for this species this year, compared to 4 last year. The Southern Hawker (top shot and above) is a recent colonist that has only been in the recording area since 2007, but is now well established, with records from 12 sites and evidence of breeding (oviposition and emergence) in several of them.
Male Black Darter near St Andrews Quay, 2012. Photo by Barry Warrington, used with permission.
Black Darter
A record of a male was submitted by Barry Warrington of this rare darter on the East side of the Yorkshire Wolds. This is a notable record as there are only a handful of records in the area, the first one from 2011 at Priory Fields, the second from the Beverley and Barmston Drain in 2013. Barry has found Black Darters in the same area, near St Andrews Quay, in 2012 (above) and 2016. Records of this species probably represent dispersing individuals, as the species breeds on boggy, moorland or heath ponds not present in our recording area.

List of species recorded in August
  1. Migrant Hawker.
  2. Southern Hawker.
  3. Brown Hawker.
  4. Common Darter
  5. Emperor Dragonfly.
  6. Common Blue
  7. Blue-tailed Damselfly.
  8. Small Red-eyed.
  9. Red-Eyed Damselfly.
  10. Azure Damselfly
  11. Ruddy Darter.
  12. Emerald. Foredyke Green.
  13. Black Darter.
In the wider area: Willow Emerald expansion
Emerald Damselfly. Mature male.
Willow Emerald male. Note lack of blue 'pruinescence', pale pterostigma with black margins and pale abdominal appendages. On side view a spur on the thorax is distinctive. Note eyes are not blue. 

Records of Willow Emerald Damselfly from Lincolnshire and a record from North Yorkshire means that there is a possibility this rapidly expanding species may make it into Hull in the near future. Fortunately, it is a late flying species, active until October, so it is worth while keeping an eye for it. The photo above was taken in a London park during the bank holiday weekend.

Tuesday, 3 September 2019

Migrant hawkers scramble competition

I'm used to watching migrant hawkers foraging over gardens, leafy streets and sheltered woodland rides, some times in groups. They are immature individuals, gathering energy away from water. Migrant Hawkers, unlike other hawkers, mature slowly, and will move to suitable breeding sites after their long immature period. During this past week I've watched them in their breeding sites in lakes and drains, where mating and egg-laying takes place.
A mature male rests briefly between bouts of searching (Pickering Park, 27th August) 

Males at the breeding site 
At one of my local parks (Pickering Park) last week, dozens of Migrant Hawkers sat or patrolled alongside marginal vegetation around the lake. The males, now fully mature and showing their bright blue spots and eyes and side yellow-green stripes often hovered in a spot, or explored the vegetation, flying well into it, searching for females.
A typical hovering male in a clearing at the marginal vegetation (Pickering Park, 27th August), offering them good views.
I saw no females, until one was captured by a male: no preliminary or courtship, the male just tackled her and positioned himself to grab her by the head. The female is then able to curve her abdomen and mate, retrieving sperm from the male's secondary genitalia at the base of the abdomen, forming the 'wheel position'. They may fly in wheel position very fast, zigzagging alongside the marginal vegetation edge or briefly rising into the air, before settling on vegetation (above).
Ovipositing female (Foredyke Stream, 1st September)
The moment when the male passes by, and sees the female.
The pair, mating.
A couple of days ago I watched a patrolling male on a ditch doing its usual patrolling routine, rising to inspect any passing individual, even paying attention - briefly rising - to birds flying over. A mated female arrived, unnoticed, and started laying eggs on live leaves well above the water line, I'd say over one metre over the water. She checked leaves and unsheathing her ovipositor, started laying into them (the eggs will overwinter inside the plant leaves, where they are protected from predation). After a couple of minutes, the male noticed her, tackled her and mating ensued. This time the pair settled briefly on plants, which allowed me to take a shot (above). Mating in Migrant Hawkers is longer than in other territorial relatives.
Two males resting near each other (Pickering Park, 27th August)
Nonterritorial males
This species is notoriously non-aggressive, even at the breeding sites. Males will even rest within view from each other (above). A patrolling male will swiftly rise to check a passing one, but the interaction is suggestive of them 'checking' that they are not a female, and letting the other individual go their way if it's a male. There is no defended territory, just males congregating on suitable ovipositing sites and searching for females, a type of mating tactic called 'scramble competition'. This appears to be the reason behind the long copulation. A territorial male mating for a long time may lose the territory to an invader, or miss extra mating opportunities. A nonterritorial male has less to lose, and therefore makes sure that he fertilises as many as possible of the females' eggs, possibly by taking time to remove any previous sperm before transferring his transfer. These patterns have been shown to stand when the copulation duration of territorial and nonterritorial drogonfly species were compared, but I haven't found specific data on the Migrant Hawker. To illustrate the pattern, the Emperor, a territorial species, copulates for an average of 10 min, while the Common Hawker, a non-territorial one, copulates for an average of 67 min. Of course, this lengthy copulation is not necessarily to the benefit of the female, who may be already mated, as the female already laying eggs, and therefore this sets the stage for the evolution of female counter-tactics, such as visiting the water as little as possible and avoiding males if they can, something I have covered before at Bugblog.

More information
C√≥rdoba-Aguilar, A., Serrano-Meneses, M. A. and Cordero-Rivera, A. Copulation Duration in Nonterritorial Odonate Species Lasts Longer than in Territorial Species. Ann. Entomol. Soc. Am. 102, 694–701 (2009).

Thursday, 1 August 2019

Hull Dragons: July summary

July is peak dragonfly season, most of the early species are still on the wing, and the last of the high summer species have emerged too. Hull Dragons has now a total of 180 records in iRecord, from 34 km2 surveyed (28 of them in July) yielding a grand total of 15 species. All but Broad-bodied Chaser, an early season species, have been recorded during July at iRecord.
Survey coverage: 34 km2.
Four new species have been added to the survey this month: Southern Hawker, Common Darter, Brown Hawker and Small Red-eyed Damselfly. Evidence of breeding has been obtained for all four but Brown Hawker.

Southern Hawker
The first record of Southern Hawker was at Pearson park Wildlife Garden pond. A number of fresh exuviae were collected between the 2nd and the 8th of July from the emergent vegetation in and around the pond.
Southern Hawker exuviae, Pearson Park wildlife garden.

Two exuviae and observations of an individual getting into a house were obtained at a private Avenues pond. Other records include an individual flying by Oak Road and two or three at Noddle Hill Lake.
Immature Southern Hawker at Noddle Hill Lake.

Banded Demoiselle
The excellent Banded Demoiselle year continues, with more records and additional sites for this species by the River Hull at Thearne, at Mill Beck, Cottingham and at the Boating Lake at Peter Pan Park (Costello Stadium).
Female Banded Demoiselle by the River Hull at Ennerdale.

Emperor Dragonfly
After a few sightings in the last week of June, it is peak season for this species, which has now been recorded at 10 sites. Males were patrolling and defending territories at East Park, Pickering Park, Foredyke Green, Ennerdale South pond and Beverley and Barmston Drain. A female was observed ovipositing at Ennerdale South pond
Male Emperor by the Beverley and Barmston drain.
Female Emperor ovipositing, Costello Stadium boating lake.

Black-tailed Skimmers
The first Black-tailed skimmer record was at the end of June, but it is in this month that they become more common. They have been recorded at 4 sites, with 8 records: Ennerdale South pond, East Park, Noddle Hill LNR and a private avenues pond. Ovipositing was observed at Ennerdale South Pond.
Ovipositing female and guarding male Black-tailed skimmer at Ennerdale South Pond. The male confronted the resident Emperor while the female oviposited.
One of several territorial male Black-tailed Skimmers at East Park.
Azure Damselfly
Azure Damselflies have now been recorded in 13 km2. Evidence of breeding in the form of mating and ovipositing has been obtained in several sites.
Azure Damselflies mating, Pearson Park wildlife garden.

Ruddy darter
Ruddy darters have been found in Noddle Hill LNR, Oak Road Lake, Midmeredales Pond (several tenerals) and a private pond in the Avenues.
Ruddy Darter, Oak Road Lake.

Common Darter
The first Common Darter in the area was at Ennerdale S Pond on the 4th July, where several tenerals were found in the vegetation by the pond. More tenerals and darter exuviae were found at an avenues private garden where both Ruddy and Common Darters have been recorded. At least two individuals and three exuviae were found at Pearson Park Wildlife Garden. This species has a long flight season and roams away from water before settling to breed so hopefully more records will be added as the season progresses.
Common darter, private avenues pond.

Blue-tailed damselfly
No matter the weather, even during cloudy or muggy days or the habitat, which includes polluted water or fish ponds, the Blue-tailed damselfly always saves the day. I was pleased to find the 'rufescens' female form at the pond in the Museums Garden in the city centre, where the species is very abundant. This form also occurs at East Park. We now have records from 18 squares in the recording area.

Small red-eyed damselflies

The first sighting of this species this year was at East Park, with dozens of pairs ovipositing in both main lake and boating lake on 13th and 25th of July. Two individuals were recorded at St Andrew’s Quay pond and there is also a record at a garden pond at Skidby. The new locations indicate that this species is likely to become more common and widespread.
Resting male.
Small red-eyed damselflies ovipositing, East Park boating lake.
Red-eyed Damselfly
More records for this species were obtained for East Park and Noddle Hill. A teneral female at Noddle Hill provided evidence of successful breeding at this site.
Red-eyed Damselfly, Noddle Hill Lake.
Teneral female Red-eyed Damselfly, Noddle Hill lake.

Tuesday, 30 July 2019

Dragonflies to watch for in August

In this fourth and last instalment of the series on dragonflies to watch out in and around Hull I present five species that have their peak flight season in August.
13. Southern Hawker, Aeshna cyanea. A large and colourful dragonfly which is hard to miss, as it likes to hawk low on shaded paths. It has a peculiar behaviour consisting in approaching people as if it was curious and was checking you out! It starts to emerge in mid-June and flies until late October, with a long peak from mid July to early September.
15. Ruddy Darter, Sympetrum striolatum. A small, compact dragonfly. Legs are black in both sexes (unlike Common Darter, see below). Males are blood-red and there is no yellow band on side of the thorax, which is reddish brown. It flies from mid June to early October. Peaks in July-August.
16. Small red-eyed damselfly, Eryhthroma viridulum. A small damselfly with red-eyed males. Close examination or photos are ideal for identification, as it differs in the pattern of blue in the tail from the closely related Red-eyed Damselfly. Short and late flight season from mid July to early September, peaking in mid August. Known from Oak Road Lake and East Park. Recent colonist, increasing its range so there is potential to discover new sites.
13. Migrant Hawker, Aeshna mixta. The first individuals tend to appear in the last week of July. Peaks end of August and has a long season, extending until November if weather is mild. It has a long immature stage and wandering habits away from water, which means that it is a species easy to record even in pond-less gardens. It hunts at tree canopy level. Smaller than other hawkers in the area. Individuals can hunt in small parties, with no signs of aggression, often resting near each other, hanging from their perches.
14. Common Darter, Sympetrum striolatum. The commonest darter in our area. They have a yellow stripe alongside each leg and yellow panels on the side of the thorax. Eyes are green or red on top and yellow below. Males are orange-red (above) with two yellow panels on the side of the thorax. Females have an all yellow side of thorax (below). Late and long season, from June until November, peaking at the end of August.