Rings of Power

When visiting ornithologist Jon Middleton remarked the airport biodiversity sites could be worth trialling for bird ringing, I thought that would be cool, wish I knew some bird ringers... It turned out I already did, I work with a few of them, I should have asked sooner, and they've been happy to help out! 

Wheatear Oenanthe oenanthe, caught and ringed under license in Gatwick Airport's North West Zone 

The North West Zone at Gatwick is a mosaic of scrub, outgrown hedgerows and floodplain meadow, maturing nicely for the past 20+ years (all created during the River Mole diversion in the year 2000), with a block of ancient woodland in the mix. Gatwick has the added interesting element of urban and brownfield habitats at the interface of natural ones, resulting in a highly diverse mix of species, including small migrating birds visiting the sites at different times of the year.

The edge of Gatwick's North West Zone

Scrub management with volunteers from the Gatwick Greenspace Partnership

Monitoring birds has been integral to Gatwick's Biodiversity Action Plan since it began in 2012. Birds are a great indicator of ecosystem health, but are also particularly important here in the context of the airport and aircraft safety. Data from our ecological surveys helps us to understand what species are using our sites and how they are faring, so that we can better target habitat works to conserve them. 

A metal BTO ring being placed on the tarsus (the area between the ankle and knee) of a Great Tit Parus major 

Bird ringing is a very intensive survey method and is therefore treated very sensitively. It involves catching birds in order to take biological measurements, placing a uniquely coded ring on the bird's leg for future identification, and then re-releasing back where they were found. Obviously this can be stressful to the bird, and welfare must always come first in this work. The British Trust for Ornithology (BTO) are the overseers of the UK Bird Ringing Scheme and the rigorous licencing procedure. Training to become a fully permitted bird ringer takes a very long time, involving many hours of work and brutally early starts in the mornings! 

Trainee bird ringers at Gatwick with Jon Middleton (right)

Information gathered from bird ringing is extremely eye-opening, such as the different species and numbers using a site, which is not necessarily picked up during our standard field-observation bird surveys. Historically, ringing work has helped to confirm where certain birds go from the UK during winter (as far as sub-Saharan Africa!!).  These days we are learning more about different migration routes, changing distributions of species and ongoing impacts from habitat loss, hunting and climate change. It is important that we collect data from more common species as well as those already known to be in decline, as we can't be sure how any species may fare in the future. 

Examples of other information collected through the ringing scheme:

• Ages
• Survival rates*
• Health/condition
• Breeding success (by the year ratio of captured youngsters to adults)
• Dispersal locations and distances
• Phenology (life cycle timings)
• Population trends

* Advances in statistical techniques have allowed survival to be calculated from recaptures of previously ringed birds. The more birds ringed, the better the chance of recovering data, all of which will be vitally important for future bird conservation. 

Airport security officer Trevor receives a demonstration from licensed bird ringer Stuart Card

One of the recent successes for our biodiversity project has been the arrival of breeding Nightingales at Gatwick, with the first confirmed modern record in 2016.  A male Nightingale ringed at the Knepp Wildlands project during August 2020 was found holding a breeding territory at Gatwick during 2021, and 'Dave' has been heard singing away again during summer of 2022.

One of two Nightingales Luscinia megarhynchos ringed at Gatwick this year. July 2022

I am hugely grateful to Jon, Stuart and Jake for donating their valuable time and energy in getting this exciting new project underway. Below are some highlights of what we have found so far, and we hope to see more species added to the list as time goes on. Watch this space!

Black Redstart Phoenicurus ochruros (male), a rare breeding species in the UK. September 2022

 

Marsh Tit Poecile palustris, September 2022

Sedge Warbler Acrocephalus schoenobaenus, September 2022

Wheatear Oenanthe oenanthe, August 2022

Redstart Phoenicurus phoenicurus, September 2022

Ringed species at Gatwick so far:

• Black Redstart Phoenicurus ochruros (Amber listed, Schedule 1)
• Blackbird Turdus merula
  
• Blackcap Sylvia atricapilla
  
• Blue Tit Cyanistes caeruleus
  
• Bullfinch Pyrrhula pyrrhula (Amber listed)
• Chiffchaff Phylloscopus collybita
• Dunnock Prunella modularis (Amber listed)
• Great Tit Parus major
  
• Green Woodpecker Picus viridis
  
• Goldcrest Regulus regulus
  
• Goldfinch Carduelis carduelis
  
• Lesser Whitethroat Curruca curruca
  
• Long-tailed Tit Aegithalos caudatus
  
• Marsh Tit Poecile palustris (Red listed)
• Nightingale Luscinia megarhynchos (Red listed)
• Redstart Phoenicurus phoenicurus (Amber listed)
• Reed Warbler Acrocephalus scirpaceus
  
• Robin Erithacus rubecula
  
• Sedge Warbler Acrocephalus schoenobaenus (Amber listed)
• Song Thrush Turdus philomelos (Amber listed)
• Willow Warbler Phylloscopus trochilus (Amber listed)
• Wheatear Oenanthe oenanthe (Amber listed)
• Whitethroat Curruca communis (Amber listed)
• Wren Troglodytes troglodytes (Amber listed)

Rings around the world: More on the Nightingales found at Gatwick Airport:

http://biodiversitygatwick.blogspot.com/2021/07/rings-around-world.html  

Rings around the world

Nightingale at Gatwick Airport (Photo by Dean Samsudin, 2020)

Back in May 2016, myself and volunteer Donald were carrying out a reptile survey in the North West Zone when a sudden burst of bird song erupted near my head; a Nightingale was the last thing I'd expected to hear that day! This is a real stand-out moment from my time at Gatwick. I nipped back that same evening to make a recording (this being back in the era of a busy night-time airfield). Ambient noise didn't put this energetic songster off...

 

Sound only clip (no image)

Nightingales arrive in the UK around late April, having migrated all the way from their overwintering sites in Africa. Checking Gatwick's pan-species list, there are few previous records of Nightingale within the airport boundary. It seemed in 1987 the Hilton Hotel car park (around 3km from the current spot) contained some good scrub habitat which was suitable for their breeding, however in 2021 this area is now a stand of semi-mature trees.

Corridors of good quality habitat are important for dispersing wildlife, especially for highly mobile species such as migrating birds. The River Mole diversion project was completed in the year 2000, resulting over 20 years later in a 3.5km length of meandering floodplain meadow, bordered by sloping species-rich grassland, graduating into scrub and mature woodland. 

North West Zone biodiversity area

Since that record in 2016, I've heard a Nightingale in the same spot on the River Mole 5 years out of 6; could it be the same bird returning each summer? Another male then set up territory along the River Mole in 2020, about 1km further downstream. This year they've both remained on site late into summer, therefore are very likely breeding. Two Nightingales on one reserve doesn't make a population, but along with increasing numbers of Song Thrush and summer-visiting warbler territories, it could indicate that our scrub and grassland mosaic is coming into peak condition.

River Mole corridor, July 2016

Our biodiversity areas are only a short stint away from the Knepp Rewilding project, itself a large 1,400ha estate of grassland, wetland and scrub, 22km away as the Nightingale flies (for comparison our NWZ site is only around 40ha). It also contains a heck of a lot of Nightingales. Anecdotally, this red-listed species seems to be having a few good years, with other additional sites popping up nearby. Could this be an overflow of birds fledging at Knepp? When local wildlife watcher Dean alerted us that the second Nightingale was sporting a silver ring on its leg this year, it meant we could possibly find this out...

Penny Green in the River Mole grasslands

The bird ringing scheme, overseen by the British Trust for Ornithology (BTO), gathers data on the survival, productivity and movements of birds, which is important in understanding why populations are changing. Recovered rings have told some pretty surprising things over the years, causing our estimates of wild bird life-spans and travel distances to be revised. It is an intensive undertaking which involves a lot of special training. Fortunately several of the ecologists we work with happen to be licenced bird ringers!

Jon Middleton is an aviation ornithologist for Birdstrike Management Ltd, who visits Gatwick Airport as a consultant several times a year. In his spare time, Jon is an avid bird ringer and after hearing about our two Nightingale territories, he offered his help with Nightingale Territory 1; the original, un-ringed male.

Just as the night was drawing in, we had success in our single mist net; a male Nightingale caught and gently handled by Jon. This happened to be Jon's first time with this species in the hand, so it was a double celebration. The first ever Nightingale to be rung at Gatwick Airport!

A few nights later, it was the turn of another crack team: Penny Green the Knepp Estate ecologist and her partner Dave, who were keen to capture the second male and check the ring reference number. It was a more intrepid route on that evening, setting up our mist net at Nightingale Territory 2...

Photo by Dave Green

Success came once again just as it was growing dark, exactly as predicted by Penny and Dave!

With the bird in the hand, Dave could clearly see the silver ring. The priority was to note down the reference number, before taking additional measurements for biometric data...

Male being checked for breeding condition

An incredibly gratifying moment was when Penny checked the Knepp ring numbers from last year; this is a match for their records! In fact, this guy was rung by Dave himself in August 2020. Having this information confirmed is super high value, showing how these birds use sites across Sussex for breeding as well as migration stop-overs. As Penny put it, this is a fantastic link between our two projects.

A check of wing length and plumage condition

What a beauty....

A Knepp-rung Nightingale on the River Mole at Gatwick (photo by Penny Green)

A bonus Lime Hawkmoth extracted from the mist net

Two Nightingales, a luxury pack of chocolate digestives, and a group of very happy ecologists at Gatwick Airport on two nights in June.

Photo by Dave Green

November Thrushes survey: Weird and the weirder

North West Zone - View from the grassy slope

The British Trust for Ornithology (BTO) Winter Thrushes survey is a nation-wide study monitoring winter visiting and resident birds and the habitats they occupy. So far, I have carried out two surveys in October and only recorded two Blackbirds. As Tom Forward (Gatwick Greenspace Partnership) has more recently been hearing plenty of Redwing around Tilgate Park, it was with higher hopes on Friday that we set out around the North West Zone.
 

Weird grass goo - at first glance it looks like wet soap powder

It was a cold and grim morning as we began our route at the water treatment pond, so it was quite a contrast to be greeted by a flock of 16 Ring-necked Parakeets flying overhead. These bright green exotics are part of a colony on Charlwood Road and whatever your view on their pest status, I quite like the sound of their uptight squawking. Looking back down to the ground, we noticed some strange and gooey deposits scattered through the rough grassland...

Slime Mould covered in dark spores

I think this is a species of Slime Mould (Mucilago crustacea), aka the Dog Sick Slime Mould; when it is freshly emerged it is bright yellow in colour! My apologies if you were eating your breakfast just now.

   We looped around the northside of Brockley Wood, entering the sheltered scrub and marsh area to the west. Here we paused as a large band of small birds passed close by us, moving through the scrub. In this single flock we counted around 20 Long-tailed Tits, 18 Blue Tits, 7 Great Tits and one Wren. You may notice my birding photos have not really improved with time.

Passing tit flock

Back-end of a Long-tailed Tit feeding in a Willow

Other birds we recorded here included Blackbird, Reed Bunting, Siskin, and a flock of Lesser Redpolls which were passing overhead. A Roe Deer suddenly hared down the track at light-speed, followed by the not-quite-fast-enough Border Control dogs which are regularly exercised by staff in this area. At the hedgerows to the south, we heard our first Song Thrush having a confusing sound-off with a nearby Dunnock, in turn seeming to do a great impression of a Blackbird.
  While ascending and descending the grassy slope, a group of 6 Skylarks wheeled overhead, calling excitedly before settling down in the distance.

Pushing on to the hedgerows south-east of Brockley Wood, the shrill 'sreee' of Redwings signalled our first winter thrush species. It seemed to be only a single pair in a flock also made up of Song Thrush, Blackbird, more roving tits, several Nuthatch and Treecreeper.

As this flock passed us by we had a quick scoot around in the Blackthorn to see if we could spot any eggs of the Brown Hairstreak Butterfly. Sadly no luck there, but I did make this gruesome yet arguably awesome discovery...

The Ex-snake

It was the remains of a Grass Snake dangling in the hedgerow, high enough off the ground that it must have been dropped there by a bird. Our guess is that one of the resident Common Buzzards snatched it, sat in the tree above the hedge and then accidentally dropped its lunch.

Skin 'n' bones

Ok, so maybe it is a bit hideous, but still an interesting find! The particularly gruesome part was that the body was wrapped tightly around a branch - a feat possibly achieved while trying to free itself or during its death throes. A pretty undignified end!
   The autumn has been fantastic for berries, so right now the birds are pretty spoiled for choice. However, this crop of food is going to be essential this winter if it turns out as cold as has been speculated.

Rambling rose suffused with rose hips

Sloe berries on the Blackthorn 

Approaching the end of the survey, we squelched through the waterlogged and boggy area by the Compost Field woodland fragment. Whilst distracted by stagnant freezing water suddenly over-topping my boots, we inadvertently flushed a Woodcock, giving a loud clatter of its wings as it shot off through the willow scrub. It took us by surprise despite this being the ideal feeding grounds for this bird! Also a new first for Gatwick since we began recording birds here... once again never a dull day with the indomitable Mr Forward!

Eurasian Woodcock (Scolopax rusticola) - RSPB Website

Our Winter Thrushes route, taking in as many of the different habitats as possible