ELEVEN DEGREES WEST

UV and the passage of the Sahara

So we think that UV has commenced his return migration. His first challenge is to traverse the western desert – a 2000 km flight to reach the straits of Gibraltar. We tend to think of this as a hazardous route, and for us it would be. But for birds – not so much...

22nd April 2016: UV sets out from Senegal, catching a few thermals on the way.  (Data: Forestry Commission England) 

There are few sizeable predators, and even fewer that would be capable of taking on an osprey. There are almost no invisible overhead cables to trap the inattentive; no mad fat bastards with guns to shoot at them; no speeding vehicles to collide with them. The skies are clear and visibility is good. It's just a matter of flying.

Of course there are no fish and precious little water in a desert – but an adult osprey in the early stages of migration does not require these things. Before leaving Senegal, UV will have bulked up, laying down fat reserves as fuel for the coming journey. And as he flies northwards, his body deploys Evolution's secret weapon for long-distance migration... “ß-oxidation.”

This is part of a three-stage process whereby lipids (stored fat) are converted into energy to power UV's flight muscles. And as a by-product, metabolic water is released at the cellular level. The numbers seem like a conjuring trick: 110g of water is produced for each 100g of fat consumed! (Okay, some other stuff is going on here as well, but it's still a remarkable adaptation.)

This biological miracle is the key to long-distance bird migration: the longer and harder you fly, the more water you get!

-WlW

Further reading:http://ir.lib.uwo.ca/cgi/viewcontent.cgi?article=1941&context=etd

Evidence for communal roosting of wintering European osprey Pandion haliaetus

The breeding habits of the European osprey have been well documented over the years but, until comparatively recently, much less was known about their lifestyle at winter quarters.

UV on 26th Feb 2016 (Vic Paine)

 A combination of satellite tracking, high-visibility rings, and diligent fieldwork from many sources has increased our understanding of this seasonal behaviour, but much remains to be discovered.

In the last ten years, bird tracking devices have used on-board GPS sensors in preference to the much-less accurate doppler VHF system. This has allowed us to observe specific movements during both day and night, and some patterns have started to emerge...

It had always been thought that ospreys were mainly sedentary during the winter season, keeping to a small activity area and seldom if ever leaving it until the time for spring migration. But the higher levels of detail now available has shown that this simplistic picture is not quite right. Many ospreys - and especially those that forage along exposed beaches and river systems - leave their hunting areas for the evening and roost overnight at favourite spots further inland, often in the same tree each night. Only where there are coastal or riparian “forests” (such as mature mangrove) do they tend to remain in place.

The reasons for this behaviour are not difficult to deduce: beaches may be warm and sunny during the day but chillier at night. Vegetation tends to be low and sparse, so predation risk would be higher. Evenings along river margins are when biting insects become most active.

Many tracked ospreys, including “Ceulan” (Blue 3C in 2012) have returned tracking info that demonstrates this transference to off-area roosting. As I studied their various data files over the years, I kept asking myself the same question: why is this bird flying five, ten, even twenty kilometres to THIS roosting tree? It must have flown past hundreds of other suitable trees to get there – so what's so special about this particular roost?

When Joanna Dailey, Pip Rowe and Vic Paine visited NW Senegal [1] in February 2016, I encouraged them to pay special attention to the roost site(s) of osprey Blue UV – a 2014 osprey from Kielder Water in Northumberland. This bird was carrying a “second generation” GSM tracking device, so we knew exactly where he was sleeping and were getting regular updates each day on his diurnal movements. (I was under no illusions about what I was asking of them: night falls very quickly at latitude 16ºN, and the west African bush is no place for newly-arrived white folks to go wandering around in the dark.)

Nonetheless, the group DID manage to observe UV at his habitual roost site – and he wasn't the only osprey using it! On successive mornings, they were able to see several birds leave the area and fly westwards towards the fish-rich Langue de Barbarie coastal strip. It was exactly what I had hoped they would find.

UV leaves his favourite baobab tree in the early morning (Vic Paine)

Later, Dirk Vanhoecke (director of the Tougoupeul Project)[2], confirmed in conversation with JD that his study group regularly see numbers of ospreys - six or seven, typically - roosting together in the wooded hinterland areas of NW Senegal. In this specific case, UV appeared to be totally relaxed in the company of other ospreys: was seen preening at perch and flying with them in the early mornings. The roost was also occupied by other species, including red-billed hornbills T. erythrorhynchus kempii.

Although large birds of prey do not form daytime flocks, communal or semi-communal winter roosting has been observed in species such as Bonelli's Eagle[3] and Montague's Harrier. In recent years, migratory lesser kestrel roosts of over to 20,000 individuals have been found in west Africa [4]. The survival benefits of communal roosting suggest that ospreys should have evolved similar behaviour and, as their overall population numbers slowly recover, we are beginning to see evidence that this is so. 

An osprey flies out over the Langue de Barbarie, Feb 2016 (Joanna Dailey)

 My thanks to Vic Paine and JD for permission to use original photographs in this article.

[Links and sources...]

[1] Kielder Osprey blog:https://kielderospreys.wordpress.com/2016/03/05/langue-de-barbarie-national-park-winter-home-for-uv-and-many-other-birds/

[2] Project Tougoupeul : http://www.tougoupeul.be/

[3] Communal Roosting in Young Bonelli's Eagles (Aquila fasciata); Marcos
Moleón, Jesús Bautista, and Agustín Madero (in Spanish) : http://dx.doi.org/10.3356/JRR-11-30.1

[4] Lesser Kestrel roosting: http://www.birdguides.com/webzine/article.asp?print=1&a=992

An Osprey For All Seasons – Blue 7H

30^th October 2015

“Bad luck! If I’d any good luck to spare he could have some. I wish we could all have good luck, all the time! I wish we had wings!” [Robert Bolt: A Man For all Seasons, II,i.]

We call it the “activity counter” - and in the world of GPS-based wildlife tracking, it can be a dreadful, portentous, doom-laden thing.
The activity counter is a column of numbers in a data file. When a bird or animal is being tracked, sensors in the PTT unit record any movements between sample points, and increment this number at each occurrence. An activity count that has NOT updated within a significant span of time, brings on a feeling that is all too-familiar to wildlife researchers:-

“Oh, no – not again...” 

Whether tracked or not, the population survival statistics for sub-adult overwintering ospreys are – as with the young of many other predator species – brutal and uncompromising. Fewer than one in four ever return to their natal regions in northern Europe to breed. It's unclear if this ratio is getting worse, but it certainly isn't getting any better. Many adverse factors seem to be at work, and the renowned conservationist Roy Dennis has estimated that some 60% of losses are due to “human activities” - either directly (illegal shooting and trapping, vehicle collisions, wire strikes, and so on) or indirectly, through loss and conversion of habitat and potential nest sites. Ospreys and other raptors that survive to breeding maturity have one thing in common: 

They all had good luck, ALL of the time.

7H was fledged at Kielder in 2014.  She became special to us in the way that these things always happen: though interest and familiarity. But 7H was not a pet - she was and remained a wild, free creature, doing exactly what her nature had inclined her to do. In following her adventures and those of her kin from Kielder Forest, we were able to learn more about this nature – and at a level of detail that may not have been achieved before.

We observed her migration with bated breath, over land and sea. We watched as she caught rides on passing ships (occasionally in the wrong direction.) We saw her learn to catch fish, and how she became gradually more proficient at this.

7H was part of my study into osprey flight strategies, proving that even very young birds of this species have an innate ability to exploit the winds and thermal air currents, and to cover vast distances with the minimum expenditure of energy. She contributed to new understanding of how first-winter ospreys settle into a feeding territory, and interact with others of their kind. She even taught us how fast she could fly, and how far... 

On her initial migration from Northumberland to Morocco, 7H traversed 5188 km. This might sound like a whole lot of flying to us, but her activity in the year AFTER arrival puts this in a startlingly different perceptive:

In the ensuing twelve months, 7H's total distance flown was an additional 9500 km – all carried out within about 40km of her “home” roost locations. Clearly, our traditional view that wintering ospreys “are mostly sedentary” does not reflect how active they are on a day-to-day basis.

 Because we were “with” 7H through the full cycle of seasons, we are able to see how those seasonal changes affected her foraging behaviour. We had confirmation that ospreys will seek for, and use, different hunting areas – even when there are more than adequate supplies in just one of those areas. And in particular, a detailed analysis of 7H's favoured perches and roost sites revealed that – to an osprey – seclusion and the absence of human disturbance are much more important than scenic views or epic landscapes.

So, yes – we have learned a great deal from Blue 7H and this knowledge is important for future conservation efforts. But 7H herself would not have cared one jot for that. Instead, she spent 399 days in Africa living the life that she was born into, free and wild. For those 399 days it had appeared that she was doing everything right: she had chosen a country where wildlife protection law is regarded more seriously than it is in some less-civilized parts of the world – such as Ireland, or Scotland.

Personally, I choose not to grieve for the passing of 7H, but just to be thankful for these many insights into her unique way of life. It has been a rare privilege and one that I will not forget any time soon.

-WlW

___________________________________________________________

Joanna has written a valedictory article about 7H on the Kielder Ospreys blog, HERE

Data provided courtesy of Forestry Commission England

"Side By Side" - FR4 and VY on migration

VY and FR4 comparative migration routes – Autumn 2015

[Click for larger]

Of the entire European population of ospreys, only a tiny proportion are

satellite-tracked every season. Of these few, it's always found that the juvenile birds follow very different migration paths – for ospreys are solo travellers and each individual chooses its own direction. But HOW do they choose these routes?

This year (2015), we are tracking Blue VY from nest site #1 at Kielder Forest. She left “home” on 30^th August and made steady progress southwards, for conditions were favourable at the time. Consistent breeze from the north and good visibility are all that a young osprey requires at this time of year.

By coincidence, another (and unrelated) juvenile started its migration at almost the same time: Blue FR4 from the Scottish Wildlife Trust nest at Loch of the Lowes passed through 55ºN about one day behind VY. The latter remained “in the lead” as the birds made their way southwards – but FR4 gradually caught up, helped in no small measure by VY's evident reluctance to make early starts! By the time both were in southern Spain, their tracks had converged both in distance and time. At roost on the 8^th September, the pair were on identical courses and only 18 km apart. (Even so, they remained totally unaware of each other's existence, and would never meet.)

This unusual situation provides some insights into the factors that might influence a juvenile's choices during migration, and the most obvious of these is weather – or in this particular case, the absence of it...

With such good conditions prevailing, both ospreys were able to follow their instincts and take the most efficient and direct routes southwards. This included the “inland” route over the western Sahara desert, which is much shorter than following the African coast as many previous tracked birds had done. However, such a “routine” migration track did not cast much light on the behaviour of individuals – until, that is, the youngsters made it into southern Mauritania...

[Click for larger]

On the afternoon of the 14^th, the young ospreys encountered their first real “problem” on this migration. The rainy season in sub-Saharan Africa was well under way – and that means variable monsoon winds out of the west and slow-moving low pressure systems that track along the desert margins. One such system was over the Senegal River valley as VY and FR4 arrived, and they found that the helpful northerly winds which had borne them all the way from Britain were gone.

As a result, our ospreys had to adopt a different flight strategy and it was the same in both cases – a course alteration SE to avoid the low pressure with its rain and poor visibility. Once across the river, they were able to turn south again, then back towards the SW on the 16^th as the weather conditions improved.

It's important to understand that the birds were not being “blown off course” at any stage. They were simply adapting their route and direction to take account of the winds and other conditions at the time – just at all other times.

And this is why birds that migrate independently can sometimes follow the same path. 

Images: Google Earth
VY Data: Forestry Commission England

Dark Skies and Dancing Ospreys

“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.” 

D. Adams – The Hitch-Hiker's Guide To The Galaxy - Ch1

If Douglas Adams had ever visited Kielder Forest, the same thought might have occurred to him. At over 65,000 hectares, it's the largest working forest in England. The main crop is sitka spruce, grown in “fields” or forestry blocks on the nutrient-poor upland soil.

It's thirty years since I was last in Northumberland. I've arrived here after a long drive from Worcestershire the previous day to meet with Joanna, and also Martin the FC ornithologist. We gather at the grandiose-sounding Kielder Castle – which is actually a rather modest 18thC hunting lodge, now housing the small cafe where visitors can view video feeds from the osprey nests. The nests themselves are in remote areas of the forest, far off the tourist trails and cycling paths around the reservoir.

Kielder Water from Leaplish

Today will be a special treat, because Martin is going to accompany us up into those less-frequented areas. After spending the winter doing interpretive desk-work on the satellite tracking data, I need to get a better idea of the layout at Kielder and how the various parts of the landscape relate to each other. To this end, we have special dispensation to enter the working forest roads – which are closed to the public due to the presence of harvesting machinery and heavy transport in those areas.

At that moment someone else appears, unexpected and unannounced, and you could knock me down with an osprey feather. It's Pip Rowe – heroine of the “Search for 7H” in Morocco and all-round good person. There is a spare seat so we pile our gear into Martin's 4x4 and set out for higher ground...

From the upper track on Castle Hill, we can look down on the weir at Bakethin and the viaduct. In the distance westward is the high ground of Black Fell (379m). Last night, Joanna and I were over there at the Kielder Observatory, built in 2008 to take advantage of this specially-protected “dark sky” zone. We were supposed to be spotting auroras but cloudy conditions on the night prevented any live viewing. However, Matt and the other staff astronomers put on a good show of “let's have a look at what you would have seen”, using existing photos and graphics on the big screen.

Kielder Observatory

It's a remarkable and interesting facility, and well worth a visit if you are in the area.  

During my reverie, Martin and Joanna have been jumping in and out of the vehicle to unlock and then secure various gates. We are now well into the “operational” part of Kielder forest, with its patchwork of plantation blocks in various stages of growth. This monoculture of trees at identical heights is one reason that FC have erected nesting platforms for the ospreys (who prefer to have a good view over neighbouring timber) and also many dozens of nest boxes for the forest's population of tawny owls. We can see one of the osprey nests in the distance but there is no sign of the youngsters there. Where are they?

The track gains more altitude. A buzzard drops from a branch and flies along the track just ahead of us, giving a great close-up view before it wheels away down one of the firebreaks. The road continues with many junctions and more gates, and by now I have little remaining idea of where we are or where we're going. It's all trees. Even the redoubtable Martin seems slightly unsure of the route – this is a seldom-visited part of the forest and only the rangers come up here on their regular rounds.

We emerge under a big and glowing sky into an area of clear-fell that has been harvested and replanted. In suitable places, FC conservation staff take advantage of the heavy machinery being deployed for planting, to dig shallow ponds. These provide much-needed habitat for amphibians and insect life, and a source of fresh water on the isolated uplands. They also, it would seem, provide bathing places for young ospreys... 

Which is exactly what the young ospreys are doing, right in front of us!

The pond itself would not win any awards in a “Most Spectacular Medium-sized Pond” competition – but obviously it's a special place for the birds, and now for us. With no disturbance from walkers, no more forestry operations for the next twenty years or so, and a clear view over the surrounding landscape, ospreys can gather here in peace. As we watch, two juveniles dance and circle each other on the far side of the slope, not a care in the world between them. They are too far away to identify by leg rings, but the sight is enthralling.

Eventually the birds depart in the late afternoon and it's time for us to move on as well. I've been deliberately vague about exactly where the Pond of the Ospreys is. It will always be a special place for Joanna, Pip, Martin and me, but the location must remain secret - so that next season another generation of birds can come here, undisturbed, to bathe and circle and dance again under the dark and shining skies of Kielder.

 -Wlw
17th August 2015

 

BATHTUB BLUES (And reds)

"In birds, the emergency life-history stage is promoted by a release of the stress hormone corticosterone. However, how corticosterone reduces the expression of parental cares remains to be clarified. One hypothesis is that the release of corticosterone may also affect prolactin levels, a pituitary hormone widely involved in regulating parental behaviours” [1]

Ospreys are a long-lived species and, as such, their reproductive strategy is spread over multiple breeding seasons. In this context, the survival of the adult female is paramount. When something goes “wrong” during the early stages of nesting, female birds have a physiological response to stress hormones that can switch away from normal nesting behaviour, and back into a mode that more resembles everyday life for a non-breeding individual. The “wrongness” could be one single event – nest disturbance, sudden reduction in food supply, prolonged bad weather, or desertion by (or absence of) the paired male – or a number of events that, taken together, add up to a “wrong” situation.

This season (2015), we have seen several high-profile examples of disrupted nesting behaviour – notably at Glaslyn (non-return of the incumbent male) and at Loch Garten (incumbent male apparently evicted by intruders.)  Such events seem to be an integral part of the osprey ecology, and have probably been occurring for many millions of years. They are a necessary thing if the species is to continue in its traditional breeding range

From ref. [1]

Scientists have discovered some of the mechanisms that lead to this “emergency life-history stage”. One of them is the effect of stress-related hormones such as corticosterones on serum prolactin – the “parental behaviour” chemical that normally takes precedence during nesting.

When prolactin levels crash in an emergency life-history stage, we see the female apparently “abandoning” or “ignoring” eggs, or even newly-hatched chicks. For human observers, this action seems to be ethically and/or morally culpable, but we must not look at it this way. The female bird has no choices in the matter: without the correct circulating hormones to trigger her behaviour, she no longer recognizes the eggs, does not know what to do with them, has no interest in them at all. Nor has she really “decided” to adopt a new strategy for her own survival or breeding success at some later time – evolution has decided these things for her.

This leaves the question of how the female's behaviour can alter so quickly (or slowly) to take account of the changing situation. To find out, we need to understand the way that hormones are created in the body, how they are disposed of, and how long these processes take – a branch of science called pharmokinetics.

From ref. [1]

In birds, egg production seems to be associated with a substance called luteinizing hormone (LH) – a glycoprotein that is released from the pituitary gland. Parental behaviour (incubation and caring for young), as we have already seen, is promoted by prolactin. The relationship between LH and prolactin levels in birds is very complicated, and both circulating factors are affected by other substances. However, we do know that they can be secreted in very large quantities, when conditions are appropriate..

And it's this basal secretion rate that provides the answer to rapid behavioural changes in birds, because NEITHER of these hormones hang around in the bloodstream for very long. The “serum half-life” of prolactin (the time taken for 50% of a given quantity to be cleared) varies according to the size of the bird, but in larger raptors seems to be around 40 minutes.

Think of trying to fill a bathtub when you have forgotten to put the plug in the plughole. If the amount of water coming in through the taps is greater than the outflow, then the bath will fill eventually – but as soon as the filling rate slackens off, the water level will start to fall again. Turn off the taps completely and the bath will empty very rapidly.

This is the way that seasonal reproductive hormones act in birds: Only if the nesting situation is favourable in most respects – and remains so, will hormones be maintained at the correct level.  The existence of an emergency life-history stage is a remarkable adaptation. For birds in general, it is not an incident of failure – it is one of the long-term secrets of their success.

(Click for larger)

SOURCES:

“How does corticosterone affect parental behaviour and reproductive success? A study of prolactin in black-legged kittiwakes” F Angelier, C Clément-Chastel, J Welcker, G W Gabrielsen, O Chastel, 2009 

“Neural Circuits Underlying Parental Behavior” C Dulac, L A O’Connell, and Zheng Wu. 2014.
Neural Control of Maternal and Paternal Behaviors. Science 345,no. 6198: 765–770.

Heatmap Haliaetus

Click for video

“Every single day and every word you say,
  Every game you play, every night you stay,
  I'll be watching you...”

Every Breath You Take  

Sumner, Matthew, Bogdanovic, Dusan (1983)

What did you do this weekend? Did you perhaps go shopping, use an ATM machine, buy a cinema ticket, hop on a bus or drive past a traffic monitoring camera? Whatever you did, somewhere a computer programme made a record of that stuff – the time, the place, the distance, the amount - and added it to a list of similar activities that other people did before you.

When Every Breath You Take was written, back in 1983, the song's sinister vision of surveillance and obsessive control did not encompass today's reality. The application of Geographic Information Systems (GIS) as a way of drawing meaningful intelligence out of large data sets, outstrips anything that could have been imagined by Sting, Orwell or Verne in their day.

The concept is simple enough: Take a list of data points, each one having a set of attributes to be studied and some form of location on a known co-ordinate system. The co-ordinates might describe any kind of spatial relationship: from bacteria growing on a Petri dish to aircraft flights on a map of the entire globe, or anything in between. Once that lot has been loaded up, the fun stuff can begin – for this is the kind of thing that computers are very VERY good at...
 

 Consider the movements of Premier League football players on a soccer pitch. During the course of a single game, the participants will roam all over the playing area. If we could obtain a table of ALL these movements (and these days, we can) and plot them on a diagram, the end result would just be a visually-confusing web of tracks and changes of direction. But by subjecting the same data to GIS processing, it becomes possible to highlight which zones the defence occupied, and which paths were favoured by the attackers before a goal was scored. Soccer, rugby and tennis coaches are now using these techniques every day, as their players carry tiny portable GPS dataloggers during training and competition. Even the referees are not exempt from this post-match scrutiny, although some of them are less than happy about such developments!

It's not all Big Brother. GIS analysis is not just used to keep an eye on us: it can benefit us and help to keep us safe. Architects use GIS to draw up the fire-evacuation plans for large buildings. It optimises ambulance routings and can predict areas of overcrowding in public spaces.

And these days, even ospreys are coming in for some analysis...

QGis "Brighton" 2.6 User interface

 I have installed a software package called QGis 2.6. Like all GIS programmes, it is horribly complicated and difficult to use, but the results are rewarding. The image at the top of this page shows the activity summary (known as a “heatmap”) for Kielder osprey Blue 7H during her stay in Morocco. GIS allows us to select different ways of looking at the data. It can measure how close one point is to another, or how many occur within a specified area. In this case, we told the computer to analyse only those points where the bird was moving, and to keep a running total of how many there were in any 200-metre radius. The result above should give an indication of 7H's favourite hunting areas, but puts less emphasis on places where she was perched or roosting.

We did a similar exercise on UV's data during his stay in Portugal and obtained very accurate results. (This heatmap has not been published because we expect him to use the same locations in future seasons)

As far as we know, no-one in Europe has used these tools to gain a picture of osprey hunting behaviour before. As the material builds up, it is hoped that the exercise will provide more insights and understanding of this subject, as it is potentially important for conservation work.

7H at Azemmour (Vic Paine)

Every dive you make, 

Every fish you take,

I'll be watching you...

-Wlw

[Data source:  Forestry Commission England satellite tracking]

QGis Software Project: http://www2.qgis.org/en/site/about/index.html