Last week the Jersey Bat Group held a week-long course with BatCRU, a bat research unit from the UK, in order to help advance the bat woodland project which has been running since 2014.
Using a combination of harp traps and mist-nets we managed to capture 151 bats of eight different species. Bats are normally relaxed in a harp trap and sometimes appear to use it as a roost. Mist-nets are useful as they cover a much larger area but must be watched constantly in case a bat flies in so it can be extracted quickly and does not get too tangled. This is only done by experienced bat workers. The bats are then identified, measured and released.
The jewel in the crown during this latest week was the capture of a Daubenton’s bat (Myotis daubentonii) at Val de la Mare Reservoir. This adds a second new species to the Jersey list this year following the discovery of the Alcathoe’s bat (M. alcathoe) in St Catherine’s woods in May (story here). A Daubenton’s bat was seen skimming over the water and, although recorded using ultrasonic bat detectors in the Island last year, had not been confirmed until now. Daubenton’s bat has a large range and is known for hunting insects low over water. It weighs between 6-10 grams and has large feet with which to capture small insects. We can now add a new island species to our list which makes a total of fourteen species.
By far the majority of bats caught last week were common pipistrelle (Pipistrellus pipistrellus) including many juveniles which was encouraging considering the poor weather conditions in June. We also caught three other species of pipistrelle: soprano (P. pygmaeus), Kuhl’s (P. kuhlii) and Nathusius’ (P. nathusii) and two long-eared bat species: brown (Plecotus auritus) and grey (P. austriacus). Finally two species of Myotis were found in the harp traps and mist-nets: Natterer’s bat (M.nattereri) (of which there were many) and the newly discovered Daubenton’s.
Whereas it was always assumed that bats in Jersey were using tree-roosts like they do elsewhere, none had previously been observed here. During the course, two female bats, one brown long-eared caught at Grève de Lecq and one Natterer’s caught at St Catherine’s Woods were fitted with radio tags. The tags, weighing around 0.3 grams and attached to the dorsal side of the bat which makes it difficult for them to be groomed off, were fitted by Daniel Whitby, a licenced professional ecologist and founder of BatCRU. We chose post-lactating females for this as the roost they may lead us to would most likely be a maternity roost. Members of the Bat Group then used receivers and antenna to track the bat using a VHF signal.
Excitingly, we discovered two tree-roosts in Rozel and in Grève de Lecq Woods. The first contained several brown long-eared bats and the other around forty Natterer’s bats. Bats were also filmed emerging from the tree-roosts soon after sunset by using infra-red camera equipment; this enabled us to count the numbers of bats within each maternity roost.
Both tagged bats moved from the original tree-roost to another tree nearby which is normal for woodland bats so in effect we have discovered four active tree-roosts whereas before the course we had not discovered any. We expect the bats to move again thereby creating more tree-roosts for us to observe in the future. The tiny transmitter could last up to 10 days unless it is groomed off sooner by bats in the roost.
During the remaining summer and early autumn we will be continuing our research and may discover more new species. We will certainly learn a lot about our local bats and collect plenty of data which will be useful for future projects.
Dr Amy Hall, Chair of the Jersey Bat Group said ‘this is a very important discovery which will likely lead to a change in woodland management and arboricultural practices in order to protect tree-roosting bats’.
Annika Binet, a research ecologist from Annyctalus Ecology who helped arrange the week-long course said “this has been a fantastic week for bat conservation in Jersey, with the help of BatCRU and the course participants we have been able to confirm some of our suspicions relating to the use of trees and breeding status of two bat species along with the presence of another species in the island”
The Bat group would like to thank the following for allowing us to conduct bat research on their land: Jersey Water, Rozel Manor, La Hanniere Farm Ltd, The National Trust for Jersey and Ken Syvret. We would also like to thank the BatCRU team for their useful input.
“This means that countries throughout the world will have fewer migratory birds reaching their shores,” Ms Wauchope said.
Arctic breeding shorebirds undertake some of the longest known migratory journeys in the animal kingdom, with many travelling more than 20,000km per year to escape the northern winter.
The bar-tailed godwit flies from Alaska to New Zealand in a single flight of 12,000 kilometres without landing.
The study predicts that, in a warming world, migratory birds will become increasingly restricted to small islands in the Arctic Ocean as they retreat north. This could cause declines in hard-hit regions and some birds could even completely change migratory pathways to migrate closer to suitable habitat.
“Climate change is also opening up the Arctic to threats such as mining and tourism, and we must make sure we protect key places for all Arctic species, including these amazing migratory birds,” Ms Wauchope said.
UQ’s Associate Professor Richard Fuller from the ARC Centre of Excellence for Environmental Decisions (CEED) said most migratory populations followed well-defined migratory routes. “This makes shorebirds an excellent group to investigate how climate change might impact breeding grounds and conservation actions that could address these impacts,” Associate Professor Fuller said.
The research modelled the suitable climate breeding conditions of 24 Arctic shorebirds and projected them to 2070. The researchers also examined the impact on Arctic birds of the world’s last major warming event about 6000 to 8000 years ago.
“Climatically suitable breeding conditions could shift and contract over the next 70 years, with up to 83 per cent of Arctic bird species losing most of their currently suitable area,” Ms Wauchope said. “This far exceeds the effects of the last major warming event on Earth, but genetic evidence suggests that even then the birds struggled to deal with the warming.”
She said that suitable climatic conditions are predicted to decline fastest in the areas with most species (western Alaska and eastern Russia), where Arctic birds are already becoming vulnerable to the “shrubification” of the tundra, and predators such as red foxes moving north.
You can read the abstract of the study Rapid climate-driven loss of breeding habitat for Arctic migratory birds here
A study tracking migrations of common cuckoos using tiny satellite tags, carried out by the British Trust for Ornithology (BTO) over the past five years, has made some very important discoveries. The results shed new light on the lives of migrating birds and point to some of the causes of this species’ dramatic population decline.
By fitting 42 male cuckoos with satellite trackers which allow each bird’s location to be logged, the researchers have confirmed that many of our cuckoos leave Britain in the autumn and fly to Italy, before crossing the Mediterranean and the Sahara to winter in Africa. The tags have revealed that the birds winter in the western part of the Congo rainforest, something that wasn’t known before.
Some birds, however, use a second route through Spain and on to West Africa, a strategy that was completely unexpected. Furthermore, after arriving in West Africa having crossed the Sahara, the birds make a left turn and make their way to the same central African wintering grounds as the birds that migrated via Italy. This is the first time that science has recorded birds taking two such distinct routes to the same destination; usually divergence in routes leads to the occupancy of different wintering grounds. Interestingly, all of the birds make their spring migration via the western route, regardless of the route used the previous autumn.
The unusual migration pattern allowed BTO scientists to assess the mortality rates associated with use of each of the two routes. Up to the point where the birds had completed their Sahara crossing there was a marked difference, with birds travelling via Italy surviving better than those going via Spain. This is the first time that differences in mortality have been attributed to differences in migration route. This new information may help to explain why cuckoo populations are in decline across much of Britain – the route that a cuckoo takes to get to its African wintering grounds could mean the difference between life and death.
Not only did survival rates of tagged birds differ between the two routes but so did the origins of the birds within Britain, leading to the third major finding. All of the birds tagged in Scotland and Wales, where the species is not so much in decline, took the more successful eastern route via Italy. Whereas across England, where 71 per cent of our breeding cuckoos has been lost during the last 25 years, local populations were made up of variable mixtures of birds taking either route.
Using information on cuckoo breeding populations from Bird Atlas 2007-11 and the BTO/JNCC/RSPB Breeding Bird Survey, the study found that across tagging locations in the UK, the proportion of birds using the less successful route via Spain correlates strongly with local population decline. This is the first time that mortality on migration has been linked to breeding population decline.
Dr Chris Hewson, lead scientist on the project at the BTO, said: “Understanding migratory birds and their population declines is very difficult because they may only be on their breeding grounds for a couple of months each year. Until recently, we had very limited information on where cuckoos and other long distance migrants went or what they did for the rest of the time. This study shows that by satellite-tracking them we can uncover not only their migration routes and wintering locations, but also information about patterns of survival that is potentially vital for understanding why they are disappearing so fast.”
Migrant birds such as the cuckoo fuel their migratory flights by storing fat in their bodies, and it seems that those feeding up in the western part of the Mediterranean might be finding this harder to do than those in the east. This could be as a result of the recent late summer droughts in Spain, reducing the abundance of the high-energy invertebrates that the cuckoos need to fuel a desert crossing. The study suggests these birds may undergo more fattening in the UK before they begin their migration than birds heading out via Italy. This would leave them especially vulnerable to the severe declines in moths (whose caterpillars are their main prey) in the south of England, where the birds breed.
There are currently 12 satellite-tagged cuckoos making their way to Africa. Anyone can follow and sponsor these birds as they make their way to the Congo rainforest during the next couple of months here.
Download the study Population decline is linked to migration route in the Common Cuckoo, a long distance nocturnally-migrating migrant here
Up to a billion birds die per year in North America as a result of striking windows. How many die here?
Both transparent and reflective glass panes are a cause for concern, misleading birds by either acting as invisible, impenetrable barriers to desired resources, or reflecting those resources over a large surface area. A high number of window strikes occur during migration, but little is known about the factors of susceptibility, or whether particular birds are more vulnerable than others.
A new report on a study of window strikes and mist-netting data from Virginia Zoological Park (Norfolk, Virginia, USA), conducted in the autumn of 2013 and 2014 focused on three factors likely to contribute to an individual bird’s predisposition to collide with windows:
What kind of bird it was
Is it a migrant or resident
Thrushes, dominated by the partial migrant American robin were significantly less likely to strike glass than be sampled in mist-nets, while (North American) wood-warblers (Parulidae) were more likely to strike than expected. The proportion of juveniles striking windows was not significantly different than the population of juvenile birds naturally occurring at the zoo. Migrants, however, were significantly more susceptible to window strikes than residents.
The study’s results suggest that resident birds are able to learn to avoid and thus reduce their likelihood of striking windows. Migrants don’t get so long to learn about their environment, especially if they are only passing through. This intrinsic risk factor may help explain the apparent susceptibility of certain birds to window strikes.
Extrinsic risks such as vegetation characteristics and habitat structure likely interact with intrinsic risk factors like experience and species-specific behaviour to ultimately determine an individual’s propensity to strike windows. It is important to consider the influence of multiple factors when considering the planning, protection, and conservation of sites that could potentially be used as stopover habitat. When resources such as food or habitat are placed in close proximity to glass structures, an increase in fatal window strikes is probable. Similarly, patterns and frequencies of strikes occurring at urban locations are highly influenced by the structure and connectivity of surrounding landscapes. Buildings with highly reflective windows, reflecting vegetated surroundings, are shown to have a high propensity for bird strikes. Great care should be taken when planning new buildings as these might impact heavily onto migratory birds.
Download the full paper Local avian density influences risk of mortality from window strikeshere
This year a sedge warbler sang down by Eddie’s Hide (St Ouen’s Bay) every day for several weeks. A lesser whitethroat sang for days at Les Ormes. These birds featured nightly on Jersey Birds and got themselves on to our Farmland Bird Monitoring. Will they have fathered any young?
A new study, by a team from the University of East Anglia (UEA) and BTO, led by Dr Catriona Morrison, illustrates how lone singing males could be an inevitable symptom of species declines. This new research focused on another summer visitor from Africa, the willow warbler, a species that has sadly gone from Jersey as a breeding birds and has experienced a 37% decline across England but a 27% increase in Scotland over two decades, according to the Breeding Bird Survey (BBS). This new study explores the potential causes of skewed sex ratios among small and declining bird populations. The findings indicate that unpaired males are substantially more common in areas with small population sizes, which are primarily found in the south-east region of the UK. These imbalances in sex ratio may be down to female choice, as female willow warblers may be selecting busier breeding locations, where habitat quality may be better and males are more abundant. This leaves male migrants unpaired in poorer sites; many – like our local sedge warbler – could be on their own for the whole season.
Speaking about the aims of the new study, Prof Jenny Gill, from UEA’s School of Biological Sciences, said: “Many migratory bird populations are declining and very small, isolated, local populations are becoming more common. If females prefer places where males are more abundant, small populations are likely to decline even faster. We wanted to find out whether this is happening.” The UEA/BTO research team used BTO ringing data from Constant Effort Sites to explore the extent, causes and consequences of variation in sex ratios in breeding populations of willow warblers across the UK. Around 8,000 birds were surveyed from 34 sites over 18 years.
Skewed sex ratios
Male-biased sex ratios occur in many bird species but are particularly common in those with small or declining populations. However, the reasons behind this and the implications for the success of local populations have rarely been investigated at large scales. Perhaps female survival is lower in areas where populations are in decline or there may be differences in the way that males and females decide where to breed? Although numbers are declining, willow warblers are sufficiently widespread and numerous to enable investigation of these issues.
New willow warbler research
Reflecting, Dr Morrison, said: “In 1994, the male-female ratio was pretty much 50:50 for willow warblers across the UK but, over time, males started to outnumber females. By 2012, males comprised around 60 per cent of the population, with sites with smaller numbers of birds having a greater proportion of males. So, for example, in sites in the north-west of the UK, where willow warblers are very abundant, the male-female ratio was still close to 50:50, but higher proportions of males were common at sites in the south-east, where there are many fewer willow warblers. Unfortunately, as time goes by, we are finding there are more male-dominated sites, probably because ongoing habitat fragmentation means that small populations are becoming more common. As expected, we found proportionately fewer juveniles in male-biased sites.
Males are highly site-faithful and females may well be preferentially joining sites with larger populations – perhaps because they are attracted to the males, or because there is more suitable habitat. Having skewed sex ratios is problematic because it means a proportion of individuals will not be able to find a mate and breed. This could potentially drive faster declines in small populations,” she added.
Male-biased sex ratios could arise from greater female mortality in small populations, for example if poorer resources in these sites compound the greater costs of breeding for females. However, the authors found little evidence that this was the case; the increasingly frequent occurrence of male bias in willow warblers is not matched by any trends in male or female survival rates. This strongly suggests that females are more likely to recruit into larger populations and thus that conservation efforts should focus on maintaining and enhancing sites capable of supporting large populations that are likely to have more equal sex ratios.
What does this mean for our bird monitoring programmes?
The willow warbler is one of many migratory species in decline across Europe and declining sharply in the south-east region of the UK it no longer breeds in the Channel Islands where it was once a common bird. If small, local populations are increasingly frequent in these species, as a result of habitat fragmentation, male-bias may be becoming increasingly common. Given that singing males are the primary records used in surveys such as the Breeding Bird Survey and as unpaired males, unlike paired males, often sing throughout the breeding season, it is more likely that they will be recorded on surveys. These lone, singing willow warblers, turtle doves and nightingales may be artificially boosting figures and inadvertently under-playing the plight of their species.
The full paper Causes and consequences of spatial variation in sex ratios in a declining bird species can be downloaded here
New research published reveals that one of our most widespread songbirds — the (winter) wren —varies in its resilience to winter weather, depending on where in Britain it lives. Scottish wrens are larger than those living in southern Britain, and more resilient to hard winter frosts.
Populations of small birds may decline following periods of cold winter weather, something that is probably linked to low temperatures and difficulties in finding sufficient insect prey. We might expect populations inhabiting regions where winters are more severe to show some form of adaptation, and this is exactly what researchers at the British Trust for Ornithology (BTO) have found in a study of one of our smallest songbirds.
The researchers used information on wren populations that had been collected by volunteers, including those in the Channel Islands, participating in the BTO/JNCC/RSPB Breeding Bird Survey, a scheme for monitoring the population changes of the UK’s common breeding birds. The researchers found that wren populations were susceptible to severe winter weather, measured in terms of the number of days with a ground frost. However, northern populations were found to be resilient to winters with up to 70 per cent more frost days than southern populations, suggesting a degree of local adaptation.
James Pearce-Higgins, BTO Director of Science and one of the paper’s authors, commented “This work indicates that each wren population is closely adapted to its local climate; there was a close correlation between the historic regional climate and the degree to which the population was resilient to severe winters.”
Using information collected by bird ringers, the team also found that wren body mass was approximately five per cent lower in the warmest (south-west) than in the coldest (east Scotland) region. As lead author Catriona Morrison, from the University of East Anglia, noted “Large individuals are likely to be favoured in colder regions due to the thermal advantage of larger size and their ability to store more body fat, and our findings match the pattern seen more widely across other species — a pattern known as Bergmann’s rule.”
The findings of this study have particular relevance to our understanding of how birds and other species respond to climate change. Although this work shows that wren populations may adapt to at least some change in temperature, they are short-lived and, therefore, probably more adaptable than most other bird species. Ultimately, the ability of species to cope with climate change will depend upon whether the future rate of warming exceeds their ability to adapt.
Channel Islands wrens, smaller than their more northerly, tough, relatives are increasingly adapting to milder winters. If the climate continues to warm as it is now, smaller wrens will become more common in all populations as this species adapts. The make-up of the bird populations we see around us in the future will depend on each species’ ability to adapt. Those that can’t will disappear but may be replaced with ones now living further south and suited to warmer weather. A look at all those egrets on the coast shows what is happening already.
You can read the full paper Winter wren populations show adaptation to local climate here
The four chicks being foster-reared in Gianna’s nest-box. Photo by Liz Corry.
At the end of May the four hand-reared chough chicks at Durrell were transferred to Gianna’s nest-box so she could help feed and look after them.
We moved them in once they reached five days-of-age. Since they hatched on different days it meant the moves were staggered. This probably helped Gianna as it meant she went from having four eggs to one chick and three eggs, followed by two chicks and two eggs and so on.
We continued to feed the chicks five times a day whilst making sure there was enough food for Gianna to cover the other feeds. The Go-Pro video below gives you a close up insight into feed times in the nest.
Normally once the chicks start to open their eyes we start wearing a black glove and feed with red tweezers. A poor imitation for a chough, but it seems to help the chicks. It means that when they are older and out and about at Sorel they are still going to be wary of people. We faced a problem with our ‘no glove, no love’ policy this year. Gianna hated the glove.
Gianna in front of her nest-box with four hungry foster chicks inside. Photo by Liz Corry.
For some reason she took great offence and would attack your hand or even just the glove if it was left on the food stand. She was the same with the latex gloves we had to wear to take DNA samples from the chicks. We tried to be secretive about using the glove, even tried distraction tactics with a second person preening Gianna. However, she quickly wised up to our actions.
Gianna overseeing two of the chicks weigh in sessions. Photo by Liz Corry
As the chicks grew and developed we reduced the amount of feeding we did and let Gianna do the majority of the work. We regularly weighed the chicks to make sure they were progressing well. The video below demonstrates how we weigh them and more importantly how attentive Gianna is, not to mention how comfortable she is with what we have to do. Apart from the initial settling-in period as mentioned in May’s report the chicks seemed to have no issues.
At three-weeks-old we added leg rings, took measurements, and DNA samples for sexing.
Student Bea holding a three-week-old chough chick in preparation for leg ringing and DNA blood sampling. Photo by Liz Corry.
Flight feathers emerging on the young chicks. Photo by Liz Corry.
We started to notice the younger chicks had feathers missing. It was subtle at first since they were still growing feathers and had naked areas.
Very quickly it was clear that Gianna was too attentive, she was feather plucking. She had shown signs of this with the chick she foster-reared last year. Back then it was only the small feathers under the chick’s chin and it stopped once he had fledged. This year she had intensified and focused on the wing coverts.
The chicks in themselves were fine and she was still feeding them as normal, but we couldn’t leave them in there until post-fledging. Birds without flight feathers don’t tend to do so well when released into the wild. It meant we had to move the chicks to Sorel earlier than planned and take back full responsibility for feeding the chicks.
Gianna was not too pleased and took a day or two to adjust. The chicks, however, coped really well. They settled into their new surroundings locked away in a nest-box in one section of the aviary.
Panoramic image showing the nest-box (right) in the release aviary and the section where the chicks will be kept separate from the free-living choughs who still use the poly-tunnel. Photo by Liz Corry.
The oldest chick could be heard calling in response to the free-living choughs when they showed up at the aviary which was a positive sign. We immediately started using the black glove and red tweezers for every feed.
The foster reared chicks in their nest-box in the release aviary. Photo by Liz Corry.
The chicks very quickly started to behave and look like proper choughs once they were five weeks old. The oldest chick, known for now as Chick U, would come to the front of the nest to try and beat the other three to the food.
Chough chicks start exploring their nest site around four to five weeks of age. Photo by Liz Corry.
Understandably U was also the first to leave the nest on 30th June. U jumped out to the shelf were the pot of food was and begged to be fed. Once it realised the other chicks in the box were still getting food it jumped back in. Chick U was very quickly followed by the other three on the same day. Their motivation to leave was completely food driven. As soon as I arrived with the food at 07:30am U jumped out to beat the queue. By the afternoon feed Chick W had realised U’s game so jumped out behind and within seconds the other two, Chick X and Chick V, took a leap of faith in despair that they might not get fed otherwise.
Captive chough chicks out of their nest. Photo by Liz Corry.
Now feed times are slightly chaotic as we have mobile begging chicks and everything is new and of interest to them. From their first water tray to small things like screw heads in the aviary timber. They won’t fly much just yet, its all about jumping and walking and occasionally misjudging and tripping over.
They are taking a real in interest in the free-living choughs on the other side of the mesh. This is obviously very advantageous for when they are finally released and mix with the group. They will be learning about the social structure of the group and observing all their behaviours. Hopefully becoming less dependent on staff, but still comfortable in their presence to make management practices easier.
Next month they will be joined by the parent-reared chicks from Durrell. Another new learning experience to embrace.
Tristan with one of his two fledged chicks at Durrell. Photo by Liz Corry.
Chough chicks have a habit of jumping out of the nest at six-weeks old to explore and feed then going back inside to take naps during the day. Photo by Liz Corry.
Chicks S and T took their first brave steps out of the nest-box back at Durrell this month. The proud parents stuck close by their chicks. One chick didn’t take to outdoor living as much as the other and went back in the nest for a bit.
Visitors at Durrell will only have a short window of opportunity to see the family out and about in the aviary. Once the chicks have started eating for themselves they will move to the release aviary and start socialising with the foster chicks.
One of the parent-reared chicks having just left the nest at Durrell. Photo by Liz Corry.
Update on the chicks in the wild nests
The chicks in the wild nests have also had an momentous month. At the start of June we made the visit to the nest sites to ring the three-week-old chicks. Glyn and Bea were joined by Channel Islands ringers Dave Buxton and Cris Sellares. Donned top-to-toe in industry standard PPE they ventured down into the quarry.
The first nest site they visited belonged to Red and Dingle. When we checked in May they had two chicks and much to everyone’s relief they still had two chicks. Except much bigger and a lot noisier.
Chick PP004 from Red and Dingle’s nest being fitted with a metal leg ring. Photo by Bea Denton.
Each chick was fitted with a metal Jersey leg ring, colour plastic rings for quick visual identification and had leg, wing, and weight measurements recorded. Small samples of blood on blotting paper were taken for DNA sexing. We should know by July which are male and which are female.
Cris Sellares with chick PP005 sporting pink and orange leg rings. Photo by Bea Denton.
Next was the turn of White and Mauve. They also had two chicks the last time we checked and two unhatched eggs. We are pleased to say both chicks had survived. As expected the two eggs had failed and the parents had removed them from the nest.
Chick PP003 having it’s wing length measured. Photo by Bea Denton.
One of these chicks proved to be a little tricky and lost a claw. A spot of super-glue was applied to stop the bleeding before it was placed safely back in the nest.
Chick PP002 sporting its new red and white striped leg ring to let people know it hatched in Jersey. Photo by Bea Denton.
The last nest to be visited was Green and Black’s who actually started nesting first out of the three pairs.We could not reach their nest last time, but had heard a chick or maybe two chicks begging. This time we were told by a member of the Ronez team that a chick had been seen on the floor of the building a day or two before. The ringing team searched the area below the nest. Glyn found several pin feathers on the floor. The nest was eerily silent.
With very little to go on and no access to the nest we do not know if the chick fell out and died or had died in the nest and the parents discarded the body. The feathers could be a result of predation, but did this happen before or after the chick had died?
Green and Black have not been behaving any differently around the aviary. They still showed up for food and had continued to fly back towards the nest site with food in their bills. We continued to monitor them all month and nothing changed. We may have given ourselves false hope. Did the nest have two chicks the first time we checked? Has only one died and the parents are still feeding a second? We will have to wait until after fledging to see if Green and Black are indeed feeding an unringed chick.
The wild chicks were due to start leaving their nest in the last week of June. From the behaviour of the parents we think this happened. However, with the persistent rain and fog there have not been many nice days to emerge from the warm, dry buildings and properly practice flying for the first time.
Watching the quarry to spot the first signs of fledglings. Photo by Liz Corry.
We have been very grateful to our old colleague Paul Pestana who has volunteered his time to help watch the nest sites. Combining all our observation notes we think we have exciting news for the July report.
Mystery fourth breeding pair?
Green and Black’s nest was not the only mystery at the quarry this month. Shortly after the visit to Ronez I was contacted by Robin Jenkins to say that one of his site foremen had spotted a nest in another building. He had noticed it because the building is regularly used by a few choughs as a roost site.
I went up at 6:45 am to check it out before the machinery was switched on. There were no choughs to be seen or heard. However, there was a nest! Trying to look into the nest with a Go-Pro on a fishing rod let me down once again. This time because the camera has no light attached. Torchlight was only possible side-on. There were no sounds coming from the nest in all the time I was there dangling a camera above the nest. However, there was fresh evidence of choughs using the building. I suspect an inexperienced pair attempted to build a nest. They might have stopped at the nest building stage. We don’t know if the nest is lined, it could just be made of twigs.
Post-modernism industrial art or a fourth nest site? Photo by Liz Corry
A return visit to the quarry at the weekend when everyone had gone home answered one question. The birds using the building were Egg and Chickay who are two-year-old females, one parent-reared, the latter hand-reared. And the male they are partnered with is no other than our infamous wild-hatched chick Dusty!
Chickay (left) with Dusty and Egg appear to have found their own corner of the quarry to set up home. Photo by Liz Corry.
The trio then added to the list of questions by disappearing into another restricted access building with food. From our observations we know they regularly take food back from the aviary to the quarry. Neither female has shown signs that she is/was incubating. Are they just caching food away from the other choughs? Is this what Green and Black are doing?
All we can do is keep monitoring the choughs and keep a lookout for any unringed juveniles being fed at the aviary in July.
The grazing flock
Less of a mystery is why the sheep at Sorel have gone from being cream coloured to brown. Its sheering season. Time to throw off their winter coats and prepare for a sizzling hot summer. Any volunteers willing to knit the sheep coats whilst they wait for summer to show its face please contact the shepherd.
The flock was temporarily locked in the aviary field and adjacent field whilst Aaron and Ewen processed them all. The sheep had a field day (pun intended) eating their way through the long grass. It is now at a height perfect for chough bills to start foraging for insects.
Towards the end of June the sheep moved back onto the headland where they are free to roam and continue working on restoring the habitat.
The 2016 Collas Crill Island Walk with the Rotary Club de la Manche was held on 18th June. Inevitably the 48-mile round-the-island route includes the clifftop home of the sheep and the choughs. We were delighted to hear that Durrell are one of the many local charities who will receive money raised by the several thousand participants. Durrell will put these funds directly into the running cost of the chough project for 2016. As a small way of saying thank you Caûvette the chough made an appearance at the Le Braye section of the walk to lend her support. Many thanks to Sarah Nugent for ‘transporting’ Cauvette to Le Braye.
Just a few of the 20, 000 plus participants of the 2016 Collas Crill Island Walk. Photo by Sarah Nugent.
Saturday 25th June saw the launch of the second year of the Track a Gannet (T.A.G.) project – tracking the movements of Alderney’s northern gannets as they leave their colony to forage throughout the English Channel and beyond. The 12 tags deployed this year are on birds from the 5,600-strong colony of Ortac and will use the 3G mobile network to transmit data on the gannets’ movements as they forage for fish. See report on the project in 2015 here.
The map shows the movements of the 2015 tagged birds – many of the areas the birds pass through and directly feed in are potential sites for renewable development in the Channel. While the proposed energy developments for the Channel could go some way to providing a source of clean energy and reducing CO² emissions for the UK, it is vital that we understand both the positive and negative impacts these developments might have. The data gathered during the T.A.G. project will go some way to providing essential data on gannet movements and how it changes from year to year, helping the collaborative team best advise on the impact developments will have on biodiversity and paving the way for more in-depth studies on the ecology and health of the waters of the Channel.
Northern gannets, the largest breeding seabird in the North Atlantic, are currently amber listed in the UK. Fortunately in Alderney the number of birds is increasing annually – especially important as the two colonies (approximately 8, 800 pairs) here make up over 2% of the world population. The longest single foraging trip from 2015 from a single bird was over 800km – a long way to go for a fish supper! This long-distance trip passed very close to several wind farm development areas, showing how far-reaching the effects of marine developments could be.
T.A.G. allows the public to follow the movements of this charismatic species in near real- time as the tags, which are attached to the gannets’ tail feathers, send updates on movements for up to six weeks every time they come into contact with a 3G mobile network. The flight paths of Alderney’s gannets can be found here. For meaningful, usable data we aim to run the T.A.G. project for at least three years – the project has already contributed to one PhD and one MSc study and we hope this will continue in future.
Roland Gauvain, AWT Manager, says “T.A.G. provides a vitally important long-term baseline for a key foraging seabird in the English Channel. Run entirely outside of the UK and EU funding process, it is dependent on the support of individuals and visitors here on our little Channel Island and the BTO and Liverpool University who have the foresight to support such a long-ranging project. Our thanks go out to our partners and we wait with baited breath to see what the birds are up to this year”!
Dr Jonathan A Green, Senior Lecturer in Marine Biology at the University of Liverpool added “We are proud to be able to assist AWT with this innovative project that combines public support with cutting-edge science. T.A.G. provides an insight into the lives of this iconic species and helps us to understand their place in a rapidly changing marine environment”.
How to see Alderney’s gannets – For anyone wanting to see both the gannets and the tags first hand they can visit the new website here to see the live map, updating the movements of the gannets.
The AWT also works closely with Visit Alderney to enable visitors to Alderney to get out and see Alderney’s seabirds by boat, especially the gannets, but also the largest breeding puffin population in the English Channel proper.
Despite a turbulent start to the breeding season the choughs at Durrell had their most productive year to date. We took a slightly different approach to our management of the pairs this year and it seems to have paid off.
We left Issy and Tristan to parent-rear in the display aviary. Out of the three pairs we have, they were the most likely candidates to succeed here despite the aviary being on-show and susceptible to disturbance. We would, of course, step in if the need arose, but in the end all they needed from staff was a constant supply of food.
Issy’s clutch of eggs visible on the nest camera monitor. Photo by Liz Corry.
Issy laid four eggs in total. On 6th May the first two eggs hatched. The chicks looked healthy and the parents were very attentive. The following morning a third chick was visible on the nest camera although it was not very active.
Sadly this last chick did not live very long and by the end of the day the parents had removed the dead chick from the nest.
The fourth egg stayed in the nest for a few days. When it was apparent it was not going to hatch the parents discarded it and focused their efforts on raising their two chicks.
We have been successful in the past with chicks hatching under their parents. However, the few chicks we have had only survived for a few days to a week at the most. Understandably staff were nervous. Visitors to Durrell may have questioned why the aviary was so overgrown when our signage clearly states that choughs require short-cropped grassland. The simple response is “Would you want a large animal with a noisy strimmer spewing grass, thistles, and weeds in front of your baby’s cot?”. We didn’t want to do anything that would distress the parents and could lead to the nest being abandoned.
The on-show display aviary became the breeding aviary for Tristan and Issy this month. Photo by Liz Corry.
However, we do need the birds to be able to forage naturally so the chicks can learn skills for surviving in the wild. The solution was to wait for the chicks to be a couple of weeks old, i.e. past the critical stage, and go in at feeds times with hand shears. Spending five minutes here and there trying to keep on top of things until the family are accepting of a ‘large animal with a strimmer’.
Tristan and Issy dutifully cared for their two chicks. Photo by Liz Corry
By the 24th, the chicks were almost adult-sized with feathers head-to-tail. They had reached a milestone never achieved at Durrell before. To mark the momentous occasion we gave them leg rings. More out of need than celebration. The best time to add rings and obtain DNA for sexing is when the chicks are three-weeks old. We assigned names to the chicks following the alphabetical system of previous years. These chicks will be S and T. Full names will be given once genders are known and they have been moved up to Sorel which should be in July.
Keeper Kathryn Smith with a three-week-old chough chick ready to collect DNA. Photo by Liz Corry
The story proved to not be as straightforward for the other pairs. We anticipated problems based on previous experience and the fact that we had a new pairing. The plan for these pairs was to allow partial parental incubation then remove eggs to artificially and/or foster incubate the remainder of the time. Once hatched, the chicks would be hand-reared for the first five days before recruiting Gianna to help foster rear until they fledge. Using Gianna as a foster mum helps reduce the chance of the chicks imprinting on the keepers. It also means we get out of having to do the early morning and evening feeds as Gianna can take care of them.
Both pairs laid a clutch of four eggs. This is where it gets complicated. We rescued one egg from Gwinny before her partner had time to do any damage. Once he was relocated she laid another three which we left with her. We only managed to recover two eggs from Mrs Denzel. All three rescued eggs were given to Gianna to carry on incubating.
Keeper Jess Maxwell with the chough eggs in the incubation room. Photo by Liz Corry
Gianna was already incubating three infertile eggs of her own so we simply swapped them over. Since Gianna is very tame she was very accommodating to staff when they needed to weigh and candle the eggs to check on progress. We were not so sure how Gianna would cope with hatching eggs having never experienced it before. To optimise everyone’s chances we relocated the eggs to the incubator at the Bird Department on 18th May a few days prior to hatch date. We gave Gianna dummy eggs to ensure she continued sitting until the time was right to start fostering.
Gwinny incubating her egg. Photo by Liz Corry
Following so far? All this time Gwinny had been incubating three of her own eggs. On the 18th we went to her nest to candle the eggs and found that all three were fertile and on-course for hatching.
Gwinny has looked after hatchlings before, but never succeeded in getting them much beyond that stage. Without a male to help feed her and the chicks we were concerned the odds would be against her.
However, we wanted her to have a chance and gain the experience. We took two of the eggs back to the incubation room and left her with one in the hope that she would cope with having just the one chick to feed. With five eggs in the incubator (three belonging to Gwinny and two belonging to Mrs Denzel) it might give the impression that the next bit was just a breeze. Sit back and wait for the eggs to hatch. Alas no.
To summarise, it feels like an injustice to the work the keepers put in, but to save on digital ink lets just say we had to assist all but one of the eggs. A few had ‘holes’ drilled into the shell to increase air-flow. Two were assisted at hatch because the chick was struggling to do so alone. One egg sadly didn’t make it to hatch because the chick was badly malpositioned and unable to even attempt to break free.
A small hole was ‘drilled’ into a chough egg to aid successful hatching. Photo by Liz Corry.
The first egg to hatch in the incubation room did so on the 21st. Two days later there was a second and the following day, with some help, the final two hatched. In order of hatching the chicks were named U, V, W, and X in hope that all four will succeed and make it to Sorel.
Chough egg hatching at Durrell. Photo by Liz Corry
Assisted hatch at Durrell. Photo by Liz Corry.
A chough chick seconds after hatching at Durrell. Photo by Liz Corry.
The egg left with Gwinny failed to hatch. She remained incubating it for a long time after the due date, but eventually gave up. The egg was taken to the Vet Department for a post-mortem.
Chicks U, V, W and X were hand-fed using tweezers every hour quickly progressing to every two hours as they grew. Feeds began at 6am and finished at 11pm. The chicks were healthy and developing well. When the first chick was five-days-old we relocated it to Gianna‘s nest where she had been patiently waiting. Within three days all four chicks were in the foster nest with Gianna.
Foster mum Gianna helped with feeding the chicks once they reached five days of age. Photo by Liz Corry.
Myself and Bea, the chough placement student, took turns feeding the chicks and Gianna. Five feeds a day from 7.30am until 5.30pm. Gianna carried out the remainder of the feeds. Occasionally trying to feed us too! Luckily Gianna took responsibility for cleaning the nest and disposing of the faecal sacs. In turn we had to clean Gianna before a new species of white-billed chough evolved.
There was a slight worry on the second day of chick V being in the foster nest as it was looking lethargic and had not put on any weight. Chick U had put on weight and was obviously being fed by Gianna. As a precaution V was moved into a heated brooder and regularly hand-fed for the rest of that day. It was then returned to the foster nest before the last feed to spend the night with Gianna and its sibling. The next day V had improved so it stayed in the nest and we target fed that chick whilst Gianna looked after the others.
Regular monitoring of the chicks meant that we could quickly see and react to anything untoward. Fortunately for the rest of the month there were no concerns. With a fledging period of 42 days there is still a long way to go.
The ‘fab four’ chough chicks in their foster nest. Photo by Liz Corry.