Revealing the fortunes of birds: what satellite transmitters tell us
Here Ian Thomson, RSPB Scotland's Head of Investigations, explains why fitting satellite transmitters to birds of prey is so important and what the data provided tells us about the these birds.
A golden eagle chick in Galloway who was fitted with a satellite transmitter before fledging in 2015 and disappeared in May 2016 (Dave Anderson, Scottish Raptor Study Group)
Ringing has been an established part of the scientific study of birds for over a hundred years. It has provided a fascinating insight into survival rates, important summer and wintering areas, and even the migration routes of a huge range of species. But, ringing has its limitations, with a bird having to be either found dead or re-trapped in order for the ring to be read.
Various developments in recent decades including the use of colour rings, neck collars and wing tags have allowed birds to be individually identified without having to catch them, but are still dependent on an observer being in the right place at the right time in order to link a bird with a location. Sometimes questions of science have to wait to be answered until technology has advanced enough to allow for that to happen.
Such is the case with the movement of birds: before the miniaturisation of GPS satellite tags, there were huge gaps in our knowledge on the daily movements of birds, important feeding areas and overnight roost sites. Satellite transmitters have changed all that. Now, the movements of a bird can be followed on a computer, allowing a fascinating insight into their daily travels, identification of roosting or nest sites and even allowing you to follow their migration across continents and oceans all with incredible accuracy.
A white-tailed eagle being fitted with a satellite transmitter in 2012 (Dean Bricknell, rspb-images.com)
It must be an amazing experience, fitting a satellite transmitter to a young bird of prey, with a feeling of great anticipation as you know you will be able to maintain a relationship with that bird for the following few years, knowing where it has gone and how it is faring.
I work closely with several people who have undergone the years of training, practice and supervision necessary to get them the unique skill-set that has allowed them to be licensed to fit satellite transmitters to birds like ospreys, red kites and hen harriers. Sadly, working for the RSPB Investigations team, my experience with satellite-tagged birds comes not in the early days of these young birds lives as they move away from their nest sites to explore the world. It happens when those experts, from a variety of agencies and organisations who are monitoring the birds, tell me they think there is a problem; a bird appears to have stopped moving, or seems to have disappeared.
One of our first experiences of this was back in 2009, when the signal given out by the transmitter fitted to a young golden eagle, named “Alma”, showed that the bird appeared to have stopped moving. Accompanied by police officers, we went to the location, and found her body, lying face-down in the heather on a grouse moor in the heart of the Angus glens in eastern Scotland. Her body was submitted to the laboratory of Science and Advice for Scottish Agriculture for post-mortem testing. Within a few days, the results came back – she had been poisoned with the banned pesticide, carbofuran.
Alma (courtesy Ewan Weston)
A follow-up operation, led by the police, searched the area, including estate buildings, to try to identify those responsible. But, as is often the case, there was not sufficient evidence found to enable a prosecution. However, the publicity surrounding this case showed very clearly that as well as giving very good information about where satellite-tagged birds were living, it could also show where they were dying.
In subsequent years, there have been further high profile cases where satellite-tagged birds have been illegally killed: the severed legs and wing tags of a red kite found stuffed in a hole in the moss on an Inverness-shire grouse moor in 2010; a golden eagle found poisoned on a grouse moor in the Strathdon area of Aberdeenshire in 2011; a golden eagle dumped under a tree after being illegally trapped on an Angus grouse moor in 2012; golden eagle “Fearnan” poisoned on another Angus grouse moor in 2013; hen harrier “Annie” found shot on a South Lanarkshire grouse moor in 2015.
Annie (John Wright)
There is a depressing pattern here – protected birds of prey found illegally killed on grouse moors. Of course, this is nothing new. In late 2015 we published a report documenting a total of 779 birds of prey confirmed as having been illegally killed in Scotland between 1994 & 2014. A significant majority of these victims were found on land where management for gamebirds, and particularly intensive driven grouse shooting, dominates the landscape.
One thing that has become apparent, however, is that there has been a decline in the number of detected illegal poisoning incidents in Scotland over the last few years. We don’t for one minute think this is coincidence, and is almost certainly linked to the increasing use of satellite transmitters. Publicity around incidents has very clearly shown that if you put poison baits out in our countryside, there is a chance that a satellite-tagged bird will become a victim, and those monitoring these birds will follow it up. The criminals killing our protected raptors don’t want to be caught, so now, perhaps, the risk of using poison is too high?
But that doesn’t mean that the killing of our birds of prey has declined. Despite claims by some to the contrary, there is no evidence to support this. What we have seen is merely a change in tactics, away from the use of poison. Contrast this with the situation south of the border, where there are no satellite-tagged eagles (indeed there are no eagles south of the border). Here the use of illegal poisons shows no signs of a reduction.
Map showing where eight golden eagles fitted with satellite transmitters were last recorded (RSPB Scotland)
In Scotland, what we are now seeing is satellite-tagged birds simply “disappearing”, as is the case of eight golden eagles in the northern Monadhliath mountains in under five years. This isn’t the first time we have seen this pattern – we have other clusters of locations where birds have simply vanished – upper Donside, for example, is an area where one satellite-tagged golden eagle was found poisoned in 2011, but four further satellite-tagged eagles, including a young white-tailed eagle, disappeared in the same area over the following three years.
Some will claim that these disappearances are the results of transmitter malfunctions, or birds dying naturally. Firstly, the experience of those who have fitted and monitored many of these transmitters, both in the UK and elsewhere, is that they are incredibly reliable pieces of kit, with malfunction exceptionally rare. Secondly, if a bird dies naturally, or if a transmitter becomes detached the transmitter will continue to give out location data, allowing it to be found. Indeed, we have recovered a number of these birds that have died as a result of starvation or tags that have come off the birds.
In short, if satellite-tagged birds die naturally, in the vast majority of cases we find them, because their transmitters keep sending out location data. In contrast, in the case of the “disappearing” birds, this is almost exclusively happening in areas of driven grouse shooting management. We don’t find the bodies of the bird, and we get no more data from the transmitter.
Coincidence? I think not.
As this year’s cohort of young raptors take to Scotland’s skies, fitted with satellite-transmitters, with the full support of some of our more progressive landowners, I’m afraid I can’t feel positive for their future. Of course, I hope they live long enough to breed and raise families themselves. But realistically, I know that a good many of them will “disappear” on grouse moors, never to be seen or heard from again.
Self-regulation by Scotland’s gamebird shooting industry has patently failed. If you want to give these young harriers, eagles and other birds of prey an improved chance of living long enough to set up their own nesting territory and fledge their own youngsters, you’ll join with RSPB Scotland in supporting this Scottish parliamentary petition, launched recently by the Scottish Raptor Study Group, and calling for licensing of gamebird shoots in Scotland.
Paul Walton is RSPB Scotland’s Head of Habitats and Species. He recently made a visit to the kittiwake colony at Sumburgh Head, Shetland, that he surveyed in the 1990s. In this blog he writes about this visit and what he discovered about the colony on his return trip. If you love seabirds as much as we do we could use your support right now. RSPB Scotland is currently asking supporters to sign a marine e-action calling for better protection of Scotland's seabirds. It is part of a public consultation on 10 potential new protected areas. If you would like to add your name and show your support for our seabirds you can do so by clicking here.
On a bleached cliff-top, sea-pinks tremble in the gusts and breezes. Fulmars cut the air with stiff wings, juddering and swaying against updrafts. Below them, kittiwakes wheel and holler, guillemots whirr in at speed, trafficking prey fish to the offspring, careering in to the breeding ledges, greeting and quarrelling, chicks begging and gulping and digesting. Gulls and skuas are patrolling, seeking the next predatory opportunity, and beneath it all a deep green Atlantic swell batters and caresses the rock face. This is pungent fertility, grace and menace on an oceanic stage.
I only have to sit here at this basement desk and imagine a seabird colony in June, and my pulse quickens. For most of the 1990s I worked for Glasgow University as a seabird researcher, based at Sumburgh Head at the southern tip of Shetland. Between April and September every day was spent on and around the cliffs, monitoring chick growth, ringing and radio-tracking adult seabirds, assessing breeding performance.
But for me, even more than the excitement of hands-on science, the most memorable activity was the hide watches. The research team would take turns to sit in small huts dug-in to the cliff-tops, weighed down with boulders. From these hidden viewpoints we watched and recorded the daily life of the colony. These watch rotas would go on for days at a time, and called for absolute concentration so that we gathered accurate data on presence and absence of breeding adults at the colony, the feeding frequency of the chicks, the timing of egg laying and chick hatching.
There is something spellbinding about spending long periods sitting quietly, unseen, and simply looking, witnessing wildlife first hand. It is less a theatrical drama unfolding, or voyeurism, more a close and intimate engagement with the reality of nature, and that is an immense privilege.
In some years there were low numbers of sandeels, the keystone prey fish species in Scotland’s marine ecosystem. Then, we would watch our study colony of 60 or so kittiwake nests reach extremes whereby an adult would depart on a foraging trip, heading out from the colony straight into the teeth of a North Sea gale, and not returning sometimes for fully 48 hours. Parent kittiwakes share the nest duties 50:50 and, during this time, that bird’s mate must remain at the nest constantly, unable to feed, guarding eggs and chicks from predators. But a small bird - and kittiwakes are astoundingly delicate in the hand - with a high metabolic rate will struggle with such long periods of forced starvation.
Seabirds are long-lived animals and most will breed several times during their lives. Some of these breeding attempts will fail quite naturally. These kittiwakes had, in effect, to make a decision: either stay on, enduring periods of starvation that, together with flying huge distances to find enough food for the young, might lead to long term physiological damage for the adult; or abandon this year’s breeding attempt and try again in future.
In the very poorest year for sandeels during our 1990s study, we watched as each kittiwake pair slowly, one after the next, abandoned their nest. The moment a chick was left alone, a gull or a skua, with hungry chicks themselves of course, would swoop in and take it. That year breeding success in the kittiwake colony was zero. But we returned to our hide the following spring to see the cliff occupied once more, with the same parent birds (the very same individuals that we had ringed, each with a unique colour combination) returning to breed successfully. We toasted them with cans of lager, and set about recording the year’s successes in our notebooks.
As the years of fieldwork proceeded, the unfolding life stories of these birds took on a sense of timelessness. The marine environment fluctuated, with big differences between the years, but I began to sense how seabird adaptations – not least their longevity and multiple breeding attempts in each adult lifespan – helped these incredible birds persist in, and as an integral part of, that marine ecosystem.
The Glasgow University research team’s colony photograph of the Sumburgh kittiwakes, 1993: each nest is marked with a red dot. Virtually all of these nests are now abandoned. c/o Prof Pat Monaghan.
It turns out I was complacent. I recently returned to Sumburgh Head at the height of the seabird breeding season. I was staggered, by what I saw. That sense of timelessness and continuity crumbled in seconds. The cliff-top kittiwake study hide that we had built back in 1990 was, to my amazement, still there – lichen encrusted and weathered, but still standing. The kittiwake colony that it looked onto, on the cliff opposite – the colony we had followed so closely and intimately for so many years - was silent. Of the 60 busy, screaming, displaying, fighting pairs, three remained, deep in the cliff cave – with no chicks visible. I could hardly believe my eyes. I left Sumburgh wounded.
This tragedy has played out across Shetland and Orkney, in other parts of the UK, beyond in the Nordic countries, and indeed across the world. Kittiwakes, arctic terns, arctic skuas, puffins – birds for which Scotland has global significance - have experienced poor food supply for such long extended runs of years that the longevity of individual adults is insufficient to maintain numbers, and huge population declines have now taken hold.
The cause is deep and fundamental shifts in the marine food-chain driven by human-induced climate change. Recent decades have seen the biomass of the zooplankton, on which the sandeels feed and depend, plummet by more than 70% in the NE Atlantic. Climate change is warming the sea surface and this is generating asynchrony in the timing of zooplankton breeding, and the timing of the annual phytoplankton bloom on which they graze. The system is out of seasonal synchrony and, to compound this, nutrient-poor warm water plankton species are beginning to replace the nutritious cold water species. Fewer sandeels is the result, with inevitable knock-on effects on the breeding success and survival of their predators - the seabirds.
The human impact on nature has, in our lifetimes, moved to a new and terrifying scale - and these climate change effects in the marine environment are for me the starkest illustration yet of how profound that impact has become.
But we can act to help. RSPB Scotland and our conservation partners lobbied hard and successfully for a Scottish Marine Act. We are pressing for the effective management of a network of protected areas at sea, where seabirds and other marine predators can feed. We are also working to build a programme that will restore as many seabird breeding islands as possible - making them free from the mammal predators, introduced by people, that decimate breeding seabirds.
If you would like to do something positive today to help protect Scotland's seabirds then we would urge you to sign our marine e-action. The Scottish Government has put forward 10 marine sites to be officially designated as protected areas for the seabirds that use them. A public consultation is open now, to get your views about whether they need to be protected. We have responded asking that they are all designated as soon as possible and you can support our call to action here. It's a great first step towards getting these birds the protection they need.
The Lodge Forest Visitor Centre in Aberfoyle is a five-star visitor attraction run by Forest Enterprise Scotland. It has a wildlife room - which is a joint project between Forest Enterprise Scotland and RSPB Scotland - where visitors can watch fantastic wildlife nearly every day, with webcams showing live nests and highlight reels. It’s been a brilliantly busy summer this year - wildlife officer Jenni Fulton brings us this summary.
During 2016, a pair of ospreys provided no end of drama in Aberfoyle. The male and female were both completely new to the site, having not settled here before. Neither of the birds had been ringed so unfortunately we didn’t know anything about their history, for example their age or where they came from. The pair quickly learned to build and defend a nest, bond with each other and produce three blotchy brown eggs.
When the first was laid, the male was curious about this new object in his nest, but the female was initially reluctant to let him observe or sit on the eggs, until he literally shouldered her aside. He spent ten minutes repeatedly sitting down and standing up, before seemingly getting bored and flying off! Luckily mum was on hand to take over again.
Despite weeks of snow, heavy rain, gales and unseasonably cold temperatures, the birds’ patient egg incubation paid off and they were rewarded with three healthy young chicks - two males and one female. At six weeks old, all three chicks were ringed and both males also had satellite trackers fitted so they can be monitored as they make their first migration to North or West Africa, where they will spend the next few years of their lives.
The osprey chicks fledged in August at around eight weeks of age, although the first flights were heart-stopping as first one, then another failed to make safe landings - clinging on to the edge of the nest before struggling to get back on board. Ospreys can perish if they miss the nest as they may not be able to take off again from a busy forest floor, and they are still dependant on fish being brought in to them by their parents.
Sadly, many ospreys don’t make it to adulthood and often we don’t understand why. But with trackers fitted, the data gathered will allow us to see exactly where these young birds go and whether they survive, which will contribute to the valuable knowledge needed to offer protection for this amazing species in future.
This year at Aberfoyle, we were also privileged to be able to watch a pair of peregrine falcons nesting on a nearby cliff edge. They found a south facing ledge with a slight overhang above, where they were warmed by the morning sun and protected from rain or snow. Four nut-brown eggs hatched after five weeks, producing four perfectly white chicks, which quickly became four boisterous young male birds.
Day after day they grew, until they were no longer fluffy bundles - but slightly smaller versions of their parents, with handsome barring on their chests and distinct black eye masks. With the ledge available to clamber about on, the chicks gradually wandered out of sight more and more often, although at meal times they were quick to reappear for a frantic feeding frenzy. Now in August, they can still be seen and heard flying around nearby.
Unfortunately owls have had a pretty tough season at Aberfoyle, with many of the nest boxes that have been installed to give these animals a home going unused. However, this has been to the benefit of other species such as gooseanders, which have been taking advantage of the spare space and moving in – some managing to lay 12 or more eggs at a time!
As the forest is home to pine martens, the owl boxes need to be positioned so these predators can’t climb down from adjacent trees and get inside. The tree trunks also have to be covered with material they cannot scale. One box we had a camera on was inhabited by barn owls and we knew at least two eggs had been laid. We eventually saw two white fluffy bundles, but then eventually only one chick reaching fledging age.
From the hide, viewing areas and on the wildlife cameras at the site, visitors can also see red squirrels, great spotted woodpeckers, jays, and nuthatches, as well as great, blue and coal tits. Recently a sparrowhawk has taken to catching unwary prey down by the feeders too.
The ospreys may have fledged and left the site now, but you can still view live wildlife footage of plenty of other species, and special films of this year’s families, at the Lodge Forest Visitor Centre. There’s also a special bat event taking place on Saturday 27 August 27. For more information, click here.