Two raptor species annually travel thousands of kilometres along the west Pacific rim, with fair numbers sometimes passing Hong Kong in spring
Early on 30 March 2022, I headed to a hilltop vantage above Nam Shan in southeast Lantau. Soon after arriving at around 10am, I scanned the horizon over the Chi Ma Wan Peninsula to the south, and saw a bird of prey approaching. It was somewhat like one of the black kites so familiar to Hong Kong people, but with slender wings and a more buoyant flight.
Through my binoculars, I saw the bird was brown on top, pale beneath, and had a whitish stripe above each eye. It was a grey-faced buzzard, and passed just east of me, heading north, followed minutes later by several more, gliding on thermals of rising air over the hillside, before they too moved northwards. I counted ten in the party, and by the time I left in the early afternoon I tallied 31.
I had been hopeful of seeing grey-faced buzzards as the winds were easterly, and with easterly airstreams persisting until around mid-April, there were more pulses of grey-faced buzzards reported by several observers. I spent more sessions watching for them on Lantau, and on 8 April counted 116, a personal best day-total for this species in over 30 years’ birdwatching in Hong Kong.
Up close, grey-faced buzzards are far from glamorous; and with a wingspan of around a metre, they lack the majesty of an eagle. To birdwatchers, however, they are notable for being unique to east Asia, and for being one of the two main species – along with Chinese Sparrowhawk, travelling the world’s only oceanic flyway for migratory birds of prey. Each year, around half a million birds follow this flyway, on epic journeys of up to 6000km between breeding grounds in eastern Russia, northeast China, Japan and Korea, and winter haunts in the Philippines and Indonesia.
For me, grey-faced buzzards have added appeal as Hong Kong is on the periphery of this flyway, and I helped show it’s possible to predict days when they pass over in fair numbers. This stemmed from a lifelong fascination with migratory birds, and ways they can be influenced by and even forecast the weather.
Fascination with bird migration and weather began in my UK hometown
I began birdwatching as I grew up in Scarborough, on the east coast of England. From a casual interest arising through family outings to the countryside, and friends occasionally asking, “What’s that bird?”, I developed a passion for wild birds.
I was lucky to experience autumn days when hundreds and even thousands of songbirds such as warblers and thrushes arrived on coastal headlands, with a smattering of unusual visitors among them. Athol Wallis, a luminary of the local natural history society and an early mentor, told me, “When we have high pressure over the continent in autumn, they bring fine weather that encourages migration, along with easterlies that can carry Siberian rarities to Britain.” Afterwards, I began avidly checking forecast charts during migration seasons.
Though I studied chemistry at my first university, Durham, I continued birdwatching in my free time, and with three friends organised an expedition to study migration in Israel. This small nation was becoming increasingly known for huge numbers of migrants, notably hundreds of thousands of birds of prey that stream north over the resort town of Eilat during spring, en route between African winter quarters and breeding haunts in north Europe. There was less information on the return journeys in autumn, and we spent almost five weeks in September and early October 1982 watching for birds of prey, in particular – hoping to shed further light on their populations and behaviour.
We chose vantages such as a rocky ridge overlooking the northern Red Sea, and spent hours-long sessions watching the skies, with binoculars and telescopes ready to identify and count any birds passing. As it turned out, we helped show there’s only a trickle of migration over Eilat in autumn compared to spring. But we did enjoy seeing a wide variety of buzzards, eagles, vultures and falcons, and I gained a liking for perching on hilltops, and counting migrating birds.
Weather and migration waves at Beidaihe, east of Beijing
I followed with a doctoral course in Cambridge; and while this too focused on chemistry, I devised plans for a more ambitious birdwatching expedition. Scant information suggested the China coast could be rewarding for migration studies – especially when Jeffery Boswall, a former BBC natural history documentary presenter, advised me that Beidaihe – east of Beijing – would be the place to go. Happily, a university library carried an obscure journal with two papers by Danish scientist Axel Hemmingsen, who had been marooned in this coastal town east of Beijing during the Japanese occupation from 1942 to 1945, and spent his time making an intensive study of migrating birds.
I read Hemmingsen’s account of what seemed an El Dorado for birdwatchers, with a host of little known and globally rare species, and no follow-up research for four decades. Putting an expedition together proved challenging, especially as China was only slowly opening after the death of Mao Zedong in 1976. Yet in mid-March 1985, four of us in the advance party of an eight-member survey team arrived in Beidaihe, a place known as a summer resort, yet with sea ice on the tideline from the lingering winter.
A map showed low hills at the edge of town, and we selected one of these for daily observations. Hemmingsen’s records indicated most spring migrants weren’t due for another four weeks; but Dr George Archibald, director of the International Crane Foundation, had encouraged our expedition, particularly as Hemmingsen had seen Siberian Cranes in late March – and no one knew how many of this highly endangered species might still occur.
Initially, it seemed the number might be zero. We spent five days on the hilltop. Though chill, the weather was mostly fine and sunny – to us, seemingly ideal for migratory flights, yet over four days only occasional geese passed by, prompting team member Steve Holloway to remark, “What do you call this, Martin? Pretty bird-less I call it.”
Then came a “wave” day, with over 1500 geese, and 881 cranes of three species. They travelled in V-shaped flocks, making for a superb spectacle against the blue sky; especially the cranes – which are akin to herons, but even larger – and included endangered Siberian Cranes that are gleaming white with black wing tips. Occasionally, crane flocks broke formation above us, soared on rising air, then regrouped and continue northwards.
It turned out that, barely noticed by us, a change in the weather had produced a southerly airstream along the coast – ideal for assisting northbound flights. During this first survey and several return visits to Beidaihe, I learned cranes are not just fair-weather fliers: most judge factors such as changing temperature and air pressure so they can maximise the chance of tailwinds and travel hundreds of kilometres between far-flung wetlands.
One autumn day, there was an indication of what can go wrong if the cranes fly in adverse conditions. A fisherman was out in a boat, and saw a juvenile Red-crowned Crane fall into the sea from exhaustion. Knowing the species was protected – and perhaps hoping for a reward – he rescued the youngster, and took it to the local government. I happened to be in town for a survey, and was called in to give advice. “You can feed it small fish, and maybe give antibiotics as for a small child,” I suggested. The fishermen said it was one of three cranes flying together: surely the parents with their offspring, crossing a bay despite a headwind.
Luckily for the crane, it was cared for until staff from a reserve arrived, and took it to their wetland, for release to join wild cranes. Countless other birds perish during migrations, however, and it’s the combination of successes and failures that develops and finetunes strategies, such as which routes to favour and preferred weather for flying.
[For more, see Beidaihe – Migration Hub of the Orient on this site.]
Connecting pulses of Grey-faced Buzzards with easterly airstreams
For many migrant species, this has led to them avoiding lengthy sea crossings, and following features such as coastlines, valleys and edges of mountain ranges – concentrating them along flyways, which are like seasonal river of birds. Eilat and Beidaihe are among places on the world’s greatest flyways, where birdwatchers can revel in the spectacle of thousands or even hundreds of thousands of birds passing over in a day, and dedicated observers record high proportions of species’ world populations: much as we recorded 652 Siberian Cranes – around 40 percent of the known world population – passing Beidaihe in spring 1985.
In early 1987, I arrived in Hong Kong, planning to live here while encouraging bird conservation at Beidaihe. I knew little of the birdlife other than a reserve called Mai Po being outstanding for wetland birds. Helped by members of the birdwatching society, I quickly learned that while there’s a rich diversity of bird species, Hong Kong does not lie on a flyway with migrants readily seen passing overhead.
So I was very surprised when, one day in March 1993, I glanced above my home on Cheung Chau and noticed a flock of Grey-faced Buzzards circling above. I grabbed my binoculars, and counted 42 birds; and later learned another 56 were seen over Aberdeen Country Park, with 228 passing Hong Kong the next day.
At the time, this seemed like just a lucky couple of days. But the next year, I co-authored a paper on connections between weather and Hong Kong birds with birdwatcher and then director of the Hong Kong Observatory, Lam Chiu-ying. After searching Hong Kong bird reports for notable sightings, we realised that spring pulses of Grey-faced Buzzards coincided with easterly airstreams over the South China Sea – and figured these birds had come from somewhere to the east of Hong Kong.
I remembered that while I was planning the first Beidaihe survey, I met Nigel Collar, compiler of the International Bird Red Data Book, who told me, “Birdwatchers in Taiwan have recently discovered tens of thousands of birds of prey passing over the southern tip of the island in autumn. They must make a long sea crossing to the Philippines.” So perhaps the Hong Kong birds were aiming to take the reverse route in spring, but were deflected by the winds over the sea.
The typical weather patterns bringing easterly winds also fit this notion. High pressure systems pushing down from China almost guarantee fine weather between Luzon and China – so, much as the cranes passing Beidaihe favour conditions for safely reaching wetlands, the Grey-faced Buzzards boost their chances of making the long sea crossing without encountering potentially fatal rainstorms. And if they happen to drift off course towards Hong Kong and nearby, that’s a small price to pay for ensuring survival.
Efforts to save Grey-faced Buzzards in Taiwan
During the 1970s, Taiwanese birdwatchers realised it was humans rather than adverse weather that posed the greatest threat to the migrating Grey-faced Buzzards. The issue evidently started with locals hunting them as precious gifts for family and friends, but snowballed as a cottage industry developed, supplying people in Japan who followed a tradition that having a mounted bird of prey could bring good fortune. The numbers traded were alarming: for instance, between 1976 and 1977, around 60,000 Grey-faced Buzzard skins were shipped to Japan.
Conservationists in Taiwan and Japan fought to save the Grey-faced Buzzard, including through awareness raising, achieving measures such as legislation that closed the Japanese market in the early 1980s, and a ban on hunting the Grey-faced Buzzard at the beginning of the 1990s. “The story of the effort to save the Grey-faced Buzzard is one that Taiwan can truly be proud of,” wrote birdwatcher Mark Wilkie in an online article.
Even with these conservation efforts, the numbers of Grey-faced Buzzards recorded passing southern Taiwan in autumn remained steady at around 10,000 from 1989 to 2003; but the tallies have since risen, to a record of 110,000 last year. Instead of being hunted, the migrating flocks have become a tourist attraction, with locals now promoting “eagle-viewing” and some former hunters working as guides.
Satellite transmitters, and a spectacular morning on Po Toi
In tandem with direct observations, researchers have also used radar to detect flocks of Grey-faced Buzzards. This revealed that in spring, the northbound birds of prey mainly travel over or near Taiwan – helping explain why, on typical days, only strays reach Hong Kong; and they can travel at up to 50km/hr. Given that Hong Kong is around 800km from the north tip of Luzon (see Spring Migration of Diurnal Raptors in Northern Luzon, Philippines, along the Oceanic Flyway in 2015 and 2016, though only abstract is not paywalled), this means at least 16 hours of non-stop flying for birds departing the Philippines to reach Hong Kong: a marathon flight, particularly for birds of prey that typically migrate during daylight hours.
Another Taiwanese study providing valuable insight for Hong Kong involved fitting Grey-faced Buzzards with satellite transmitters. After four individuals headed south for winter, they were tracked during the spring migration, including their flights from Luzon. While three passed over Taiwan, one made landfall on an island in western Guangdong. “It was hampered by several days of strong northeast monsoon winds, but it fought its way across the sea,” reported an article in Taiwan Today – supporting the conclusion of Lam Chiu-ying and me that pulses of these birds of prey in Hong Kong result from easterly airstreams deflecting them off course.
Based on his extensive observations of migration on Po Toi, Hong Kong birdwatcher Geoff Welch believes many birds arriving from over the sea in spring first rest on Dangan and other islands south of Hong Kong. These include Grey-faced Buzzards – and Chinese Sparrowhawks, which are more abundant along the flyway, and pass a little later in spring. On some days, Welch witnessed flocks of these birds passing Po Toi, most notably on 14 April 2010.
“1440 Chinese Goshawks [aka Sparrowhawks] flew through Po Toi this morning between 9.30am and 11.30am, a spectacular sight,” Welch reported on the Hong Kong Birdwatching Society forum. “This movement took place right through the harbour, the birds passing at heights mostly below 200 feet in a steady steam with more than one thousand birds between 10.30 and 11.30am.”
After the Grey-faced Buzzards – Chinese Sparrowhawks
Unsurprisingly given they also travel the oceanic flyway, these sparrowhawks occur in similar weather to Grey-faced Buzzards – and with further easterlies during the second half of April this year, I headed to Lantau in hopes of seeing them. While previous Hong Kong records were mainly from lower, coastal sites, Lantau-based naturalist Paul Aston had tried a higher lookout, near Ngong Ping – the roadside Windy Gap lookout, finding it productive for birds of prey, and I made several morning visits to this area.
Soon afterwards I also tried a hilltop above this, behind the Big Buddha [see Birds of Lion Head Mountain and Ngong Ping], from which I could gaze out across hillsides cradling Shek Pik Reservoir, and hope the Chinese Sparrowhawks were coming. I was not disappointed.
Sparrowhawks in twos and threes, and parties of up to eight, sometimes arrived from the south, circling way below, and rose before cresting the hills and cruising north. Others seemed to appear from thin air right in front of me, so close I could admire their blue-grey upperparts and heads, rusty-orange bellies and pale underwings with dark tips. Chinese Sparrowhawks are smaller, more agile than Grey-faced Buzzards, and I watched seven spiral upwards till almost lost from view against the blue sky.
Though I missed a morning when a lucky observer saw 180 Chinese Sparrowhawks heading over Lantau, I did manage a three-figure tally – 101 birds – on 3 May, when for an hour or so they streamed over the hills and I noted 15, 4, 15, 16, 6, 1 and 12 in quick succession before the passage tailed away. By then, even early mornings were hot, and the spring migration was coming to a close. Two days later, I returned and recorded a very round number of migrating birds of prey: 0.
More to learn, including in autumn
In autumn, the Grey-faced Buzzards and Chinese Sparrowhawks are again travelling the oceanic flyway, but only few are seen in Hong Kong – and at least some of these might be individuals taking an alternative, mainly overland route via the Malay Peninsula, as they occur along with species like Oriental Honey-Buzzard, which is known to favour the long way round to Indonesian winter areas. [Check out information from counts at Khao Dinsor, southern Thailand; inc on abundance of birds and timing of the migration there.]
So why do many Grey-faced Buzzards and Chinese Sparrowhawks choose to follow the oceanic flyway, while others opt to mostly fly overland, even though they might breed and spend winter in similar areas? As yet, no one has the answer.
For myself, I’m also curious about what this autumn might bring. Usually, migrating birds of prey are sparse here in autumn. But last year, several hundreds were seen, including Amur Falcons that undertake astonishing journeys from northeast Asia to India and onwards to Africa. Was this a fluke, arising from powerful northeast monsoon winds, or might time spent watching, such as on the “new” Lantau vantage, prove rewarding? I’m hoping the latter proves correct.
But if the autumn migration’s a flop, at least the views are good. And I can reflect that, especially while almost confined to Hong Kong in these Covid times, we’re lucky – even privileged – to witness something of the migrations of the Grey-faced Buzzards and Chinese Sparrowhawks, and gain insights regarding their strategies for surviving and thriving by undertaking long, perilous journeys along the west Pacific rim.
[Update 3 October 2022: after quiet sessions last month, some bird of prey movement in first three days of this month, including second Booted Eagle for Hong Kong: so “skywatching” may prove rewarding in days and weeks to come.]
Written for the South China Morning Post.
For further info, see article I’ve written on another site: Spring Migration of Grey-faced Buzzards and Chinese Sparrowhawks in Hong Kong.