Tracks of routes taken by Pallid Swifts from the Gibraltar National Museum breeding colony in 2018-19 (four birds) and 2019-20 (three birds).
Results from satellite trackers fitted to Pallid Swifts at a colony in Gibraltar have recently been published in a paper in PLoS ONE.
The data revealed that Pallid Swifts from the colony spend their annual cycle in several well defined areas. After leaving the breeding colony in mid-August and crossing the Sahara Desert, birds spend this period until early November (roughly 2.5 months) in the Sahel zone.
From there, swifts spent about one month in the Sudanian savannah zone (between 10° and 15° N), followed by around four months in the Guinea forest zone, between 0° and 10° N. The sole Pallid Swift that was tracked over both study years appeared to show remarkable consistency in the areas visited, and the timing of its movements between years.
Although there appears to be a strict adherence to specific latitude bands at specific times of the annual cycle, the results suggested that birds will move widely on a longitudinal basis.
The full paper is open access and can be found here.
Dr Keith Bensusan, the General Secretary of GONHS, joined when he was a young passionate eight year old birdwatchers.
Years later that passion has not waned and in fact forms a large part of his life with holidays with his partner always having some form of wildlife involved.
Dr Bensusan is avid bird lover, who shares this passion with thousands, but one question he cannot answer is ‘Why birds?’
“I cannot answer that question because I have been interested in animals ever since I can remember. I can’t give you an answer as to why because I do not remember,” he said.
“But I do remember the first bird book that I ever owned and I wrote my name and address on the inside cover and my name and address are both misspelt, I was five years old when I got that book.”
A book he still has to this day.
“My parents were always very encouraging, extremely encouraging, and I did not realise when I was a child just how encouraging they were and how willing they were to take me birding in Spain for example and put up with hours of boredom whilst I did my thing,” he said.
At the age of eight he joined GONHS following the prompting from the head teacher, Mrs Canapa, in his first school which was St Joseph’s Infants brought in a bird to show the class.
“She brought a bird into the class and showed the class and said ‘can anyone tell me what this?’ and I put my hand up and said that is a swift,” he recalled.
“And, she started asking me how I know and I said well I’m into birds.”
She was a member of GONHS and she suggested that he spoke to his parents as he really should become a member.
Since then, his passion and knowledge for birds has grown.
“As a child I was a very obsessive bird watcher. I used to bird watch every day really,” he said.
“Mainly in Gibraltar but in Spain as well. As I said my parents used to take me into Spain as well, but as a young teenager other birdwatchers in Gib would take me as well.”
The places he used to visit to bird watch in Gibraltar has not changed much over the years.
Those places that were particularly accessible to him were the Alameda Gardens, which he is now the director of, Europa Point to watch seabirds and the North Front cemetery when he was a pupil at Bayside as he would pack his binoculars in his school bag.
“The cemetery is still a hotspot but I have to say it used to be much better for birds back then because the vegetation was managed in a more wildlife friendly way or perhaps it was not managed,” he said.
Jew’s Gate, the top of the Rock, throughout the Upper Rock are also hotspots.
If he went to Spain his destination would depend on the type of birds they were hoping to spot.
“Andalucía in general is very good for birds but the most famous site for birds in Andalucía is possible Donana which is a few hours away from Gib but we would go there occasionally and we still do. But the province of Cadiz is very rich in birds because of the variety of habitats that it has. It has reasonably high mountains in the Grazalema area, all the way down to the marshes on the Atlantic coast and beaches.”
“And, particularly because of the Strait of Gibraltar. Because, it is a bottleneck for migrating birds. So throughout the area really there are better and worse places but there are lots of fantastic places to go birding in this part of the world.”
Because of his travels he has been able to see the vast majority of birds that he wanted to see.
“I am lucky enough that my partner is a naturalist too and that means that all of our holidays are wildlife viewing holidays. So we have travelled a bit and seen quite a few things,” he said.
There are places in the world that are spectacular for birds that he has yet to visit such as Neotropics. He had a holiday planned to Costa Rica before Covid-19 hit globally, however, they are still hoping to go this year. The couple are used to travelling places such as Africa and Asia.
“I really enjoy birding in Africa because of all of the really exotic birds that you get there but there is also the familiarity too in that a lot of the bird families that are represented there are also represented in Europe,” he said.
“Or to put it another way all of the European bird families are represented there. And, the other thing is that you get to see some of the birds that visit during the European winter and you get to see some of the birds that you are familiar with in Europe alongside these tropical African birds.”
One place that surprised him more than he had expected was New Zealand.
“I never really planned on visiting New Zealand as spectacular as it is because there are relativity few birds because it is such an isolated country. But, what there is in New Zealand is quite spectacular and different,” he said.
“So we saw a couple of species of kiwis which are just amazing and that would be the type of bird you would say ‘I would really like to see a kiwi’. And, the sea birding there is unrivalled and better than anywhere else on the planet. So if there was any where that was unexpectantly enjoyable and even in spite of the low number of species present it would be New Zealand.”
When he is not travelling or planning trips he can spend hours every week bird watching locally and given Gibraltar’s location in the world this means the birds he can see change throughout the year due to migration. Especially in February to May and July to November, where you can get a lot of birds and a bird watcher does not know what to expect. The number of birds are often in the thousands and on occasion the tens of thousands.
“The other thing is that not only do we have that visible migration that even people on the streets are aware of, the birds of prey going north during the spring and back south to Africa during autumn,” he said.
“You have that but you also have songbirds coming through. Obviously they are not that visible on a greater scale than the birds of prey because there populations in Europe are far larger than those of the birds of prey. Because, they are tiny little things that occupy small territories.”
“And we have sea bird migration too in and out of the Mediterranean. So even though most of the Mediterranean I would say is fairly boring for sea birds the Strait of Gibraltar is very good for sea bird watching.”
If anyone is interested in getting into bird watching Dr Bensusan suggests Gibraltar is an easy place to get into birdwatching as there are birds all around.
“Buy a pair of binoculars and talk to GONHS about joining,” he said.
“There are a number of very good and experienced bird watchers in Gibraltar. We have a field centre at Jew’s Gate where bird ringing takes place. We regularly watch birds of prey and seabirds and we also lead outings in Gibraltar and Spain. Where people can learn not only about birds but also other groups, even plants and insects and things like that. If you develop an interest in wildlife then you should be interested in all groups and not just the group you focus on.”
There are two reasons that keep Dr Bensusan interested in birds, one is a fascination with the natural world and an insatiable appetite for learning about the natural world, and the second is a simple compulsion he has for birdwatching.
“It is not something I could ever stop doing,” he said.
The blackcaps waited for dusk so as to avoid predators, and only then did they take off. Swarms came up from the gardens below where they had been waiting motionless and all flew up from the bushes and into the dark and empty sky, never to be seen again. Their heading was impeccably and uncompromisingly narrow and accurate – due north.
A few minutes later it was dark. Geraldine and I negotiated the steep and narrow paths back to the road with the aid of our torches, buzzing with excitement at having observed something fleeting, feeling privileged that Nature had allowed us into one of its secrets. Now it was gone but the memory lived on. It was February 1977 and we had been ringing birds at Jews’ Gate.
The impressive eagles and kites passing over our heads tend to steal the limelight but how many of us are familiar with, even notice, the little birds that skulk in the undergrowth? This time of the year sees the migration of a small and dull-looking bird, but one which can impress us by its achievements in the constantly changing world of migratory birds.
Let’s start with a brief introduction to this bird: the blackcap, known scientifically as Sylvia atricapilla.
The blackcap is a warbler. It is typically described as an insectivorous bird but in actual fact, like many other such birds, it is omnivorous. In the winter in particular, when insects are scarcer than during the rest of the year, blackcaps will eat fruit and even take nectar from aloes. In Gibraltar, their favourite fruit is that of the wild olive.
I’ve been very familiar with the Gibraltar blackcaps since the 1970s, when they became study subjects for my doctoral thesis while at the Edward Grey Institute of Field Ornithology at Oxford. The account at the start of this article dates back to those early days but blackcaps continue to pass, year-in, year-out, in a timeless exercise of genetically-controlled, physiological determinism.
Blackcaps are small birds, actually at the larger end of the scale as far as warblers go, but small all the same. The male has a distinctive black cap which gives the species its name; females are distinguished from males quite easily as their caps are brown. You can see the difference in some of the photographs accompanying this article.
I found that blackcaps ranged in weight from 17 to 19 grammes for much of the year but this changed at the end of February and early March, about now, when the migration north started. Geraldine and I used to catch these birds at Jews’ Gate and in spring our record bird reached 31.5 grammes, an approximate weight increase of 75% in a few days!
I compared these weights with spring blackcaps that had just crossed the Sahara Desert on their way north and had been caught in oases on the edge of the desert. These birds were emaciated and the leanest blackcap weighed a meagre 11 grammes, just over a third of the weight of our champion blackcap!
In last week’s article I wrote about male short-toed eagles preceding females during spring migration. Blackcaps are the same and for similar reasons: territorial imperatives related to eventual mate selection. The passage at this time of year is overwhelmingly dominated by males, the females coming later, from mid-March to April.
Most of us wouldn’t notice this migration at all but, believe me, it can be overwhelmingly spectacular. As with many things in Nature, you have to be in the right place at the right time or you miss it. With blackcaps in spring, you have to hang on until the last rays of the sun have gone behind the hills to the west. At Jews’ Gate we would start to hear the “chack-chack” calls of the blackcaps and, suddenly, the bushes seemed to come alive as blackcap after blackcap woke up from their daytime sojourn.
Some blackcaps winter with us but many of these birds had arrived from the south. Many had spent the winter in Morocco and others had ventured south of the Sahara Desert, wintering in the acacia steppe belt in Upper Volta (now Burkina Faso), Mali and Senegal, and also in wetter areas to the south.
It was these birds, which had wintered to the south of us, that were now pushing north after resting and recovering energy ahead of the last lap of the journey which would take them to Germany, the Netherlands, Belgium, France and the United Kingdom.
Their migration takes place at night. They navigate using the night sky as a map; cloudy nights tended to ground many birds, producing spectacular “falls”. During the day, the lean ones were active and hunted insects. They would stay up to a week while they laid down fresh fat deposits ahead of their flight north. The heavy ones just stayed put under a branch, conserving energy until the setting sun was the cue to get going once again.
There are advantages to night migration: you escape the attention of many predators and you get a chance to rest, feed and drink during the day. Many birds do this.
Today, blackcaps are generously allowing us to observe the process of evolution in a very direct way. Birds from south-western Germany have traditionally headed south-west in autumn. That brought them to our part of the world for the winter. In recent years, scientists have detected a change in the pattern. Many birds now head west to north-west instead, an unusual trajectory for a European bird in the autumn. These birds end up in the United Kingdom.
Now, presumably some birds have always taken this “wrong” flightpath and eventually died, not being able to survive the harsh winters. But now they survive. They do so because they have taken to visiting gardens where food is put out for birds throughout the winter. We are, inadvertently, changing the course of blackcap evolution!
These blackcaps are spending the winter closer to their German breeding grounds so they get back there earlier in the spring than the ones that come to us – they have shorter distances to travel. So, they may well be getting the best territories, producing more offspring that will migrate west/north-west instead of south-west, and radically changing the pattern of blackcap migration. That will work provided we keep putting out winter food in gardens in the UK.
I want to close with another Gibraltar story. When we were studying blackcaps here in Gibraltar, we noticed that we could distinguish two different kinds. One was smaller and darker than the other. These smaller birds also had shorter, more-rounded, wings.
What did this mean? In time, we came up with the answer. The small and dark ones were Gibraltar blackcaps, born and bred here. They were with us all year. They didn’t migrate at all and had no need for long, pointed, wings. Short, rounded, wings made them more manoeuvrable in the dense vegetation of the Upper Rock. The others, larger, longer-winged, much more streamlined, were perfect flying machines that were capable of undertaking journeys of thousands of kilometres.
It was these birds that had performed for us at Jews’ Gate. At the same time, the Gibraltar birds just carried on with their daily routines, wondering when these intruders would finally leave them in peace!
Research carried out by Gibraltarian scientists was recently presented at the 6th International Swift Conference, recently held in Segovia, Spain. The biennial conference was due to take place in 2020 following the 2018 conference in Tel Aviv, Israel but had to be postponed due to the COVID 19 pandemic.
A statement from the Government follows below:
This was the first time this international conference was held in the Iberian Peninsula. The famous Roman aqueduct that crosses the host city of Segovia is home to an estimated 2,000 pairs of common swifts (Apus apus). The event attracted over 100 researchers and experts from all over Europe and the Americas representing the countries of Austria, Belgium, Brazil, Cuba, France, Germany, Gibraltar, Ireland, Netherlands, Switzerland, the United Kingdom and the United States. Over 40 presentations were delivered covering the topics of swift biology and ecology, conservation of breeding colonies in cultural heritage monuments and urban landscapes, New World swifts and environmental awareness.
The research, conducted by scientists working at the Gibraltar National Museum and Gibraltar Botanic Gardens, Associate Campuses of the University of Gibraltar, along with members of the GibraltarOrnithological andNatural History Society (GONHS), used GPS technology to track pallid swifts (Apus pallidus brehmorum) from a single breeding colony in Gibraltar (in the attic of the Gibraltar National Museum) over two years. Their results, previously published in the journal PLoS One, revealed the movement of birds between specific regions within the non-breeding geographical area at specific times of the year. The tracking of a single individual showed remarkable fidelity to the areas visited between years. Furthermore, two pallid swifts tracked over the entire eight-month non-breeding period, while in Africa, gave no indication of coming to land, supporting previous findings of an airborne existence in swifts outside the breeding season. In addition, the crossing of the Sahara Desert to and from breeding grounds is remarkably fast, with one individual crossing it in just over a day.
Tyson Lee Holmes of the Gibraltar National Museum and PhD candidate at the University of Gibraltar, presented the study entitled “Birds with multiple homes. The annual cycle of the pallid swift (Apus pallidus brehmorum)” on the team’s behalf and was well received among the many delegates. The full publication is available from the peer-reviewed open access scientific journal PLOS One: Birds with multiple homes. The annual cycle of the pallid swift (Apus pallidus brehmorum)
The 7th International Swift Conference is due to take place in Trieste, Italy in 2024.
Minister for Environment, the Hon John Cortes, commented: “It’s great to once again see scientific research emanating from Gibraltar being presented internationally. Bird migration is a topic of particular relevance and in which Gibraltar can make a significant contribution given its geographical location.Collaboration between the different entities working in this field is especially welcome, and I want to congratulate all those involved on their research."