In July and August 2016 I joined a wader expedition to the western side of Kamchatka; a long peninsula of land in sub-Arctic far-eastern Russia. The precise location was the Belogolovava river estuary, which flows into the Sea of Okhotsk. In winter this region is covered in snow but between May and October the ground softens and waders return to breed here and to the north around the Arctic Circle.
In fact to be more precise, waders breed across a wide range of climatic zones from within the Arctic Circle, to sub-Arctic regions as well as well to the south. The vegetation at these different latitudes varies and so attracts different wader species that have species-specific preferences for different nesting environments. The north-western side of Kamchatka is a sub-Arctic region consisting of lowland tundra, remnants of Targa forest, coastal marshlands and tidal mudflats. The Long-toed Stint, Grey -tailed Tattler, Common Greenshank, Wood Sandpiper, Lesser Sandplover and Dunlin, among others, nest in these marshlands and the Far Eastern Curlew nests on the lowland tundra (see photos below).
Other wader species nest to the immediate north of Kamchatka in the Arctic and high Arctic but fly south after breeding to feed on these intertidal mudflats. The dominant species that breed directly to the north are Ruddy Turnstone, Red Neck Stint, Black and Bar-tailed Godwit and Great and Red Knot (see photos below).
After hatching, wader chicks are able to walk almost straight away; they can tolerate a wide range of temperatures and are also able to feed themselves. Parenting is limited to showing young the best and safest feeding areas and signalling danger from predators, such as approaching Raptors, Skuas and larger Gulls. These tasks are left to adult males with female adults usually departing the nesting area soon after hatching has taken place. Within two to three weeks males also leave the fledgling young to fend for themselves. Within a further two weeks or so the young leave the nesting area and fly to nearby intertidal feeding grounds.
This means that post breeding there is a continuous cycle of waders arriving on the intertidal mudflats over a period of about 10 weeks; first females and then a mix of females and males, then juveniles mixed in with these adults and eventually flocks that are predominantly young birds hatched a few weeks earlier. Despite a continuous flow of new arrivals on the mudflats, the population in the estuary remains constant at about 30,000 birds per day. This suggests that while there is a continuous flow of waders from the nesting grounds there is also a continuous number setting off on southern migration. On several evenings in any given week between 1000 and 10,000 waders leave the estuary.
Adult waders arriving at the intertidal mudflats behave differently to juveniles. Adults quickly occupy the productive feeding areas of the mudflats. Different species dominate different parts of the mudflats where their food preference is most abundant. Great Knots prefer molluscs (bivalves) on or near the surface of the central and south-western tidal zones. Black-tailed Godwits probe for polychaetes at what appeared to be the most abundant middle of the south-western mudflats. Eastern Curlew concentrated to the far end of the south-western edge of the intertidal zone. They mainly forage for burrowing prey such as crustaceans like crabs and shrimps. They use visual surface clues in the mud before probing. Looking downward to the mud surface and moving slowly they will then quickly probe deep into the mud, pulling out a crab, lifting their heads and swallowing. These abundant species tended to be in quite dense flocks, sometimes lifting together to move to other parts of the mudflats to feed. The density of the flocks probably indicates the specific areas of best food supply but also acts as some protection form predating Raptors and Skuas.
Juvenile Knots and Godwits arriving from the nesting grounds tended to join other juveniles to form small flocks (5 to 30) on the tundra close to the mudflats. They move onto the edge of the mudflats and if disturbed moved back onto the tundra. While they displayed their species specific feeding actions by probing (Godwits) and pecking and probing (Knots) or turning over small stones (Ruddy Turnstones) they did so in areas largely devoid of any abundant food supply. When they arrive they are inefficient feeders. After several days they joined up with adult flocks and began to feed more efficiently although remain on the edge of the flocks in what appeared to be the less food productive areas. Being on flock edges made them more prone to predation than the adult birds towards the centre.
Resighting of birds that had been caught and had small colour plastic tags attached to their legs for research purposes suggested that birds at this site could spend up to two weeks feeding before beginning southern migration.
Migration south occurred mainly in the evening. Migrating flocks tended to be dominated by the same species but it was also common to have smaller numbers of other waders join. So for example, flocks of Black-tailed Godwit set off with Common Greenshank mixed in at the edge of the flock. A common pattern was for a flock to lift off the mud surface rising 50 to 300 metres into the air and then to glide downwards again to settle on the mud. These ‘lifts’ would occur several times before eventually a flock would continue to climb, forming a rough V shape to head South West over the Sea of Okhotsk.
Mudflats and the surrounding tundra on the western side of Kamchatka provide a transition environment between nesting and migration for both adults and juveniles coming off the breeding grounds locally and for many waders that breed to the north. Both adults and juveniles feed and put on fat reserves here before migrating southward. While adults use existing knowledge and feeding skills to locate and exploit the most abundant food source zones of the mudflats, juveniles learn how to achieve efficient feeding through joining up with adult flocks.
The study of survival factors and rates needs exploration as climate change alters the synchronisation between breeding, food supply, migration timing and climatic conditions in this region.
What does seem apparent is the importance of these transition sites, like the Belogolovava River estuary in western Kamchatka, at the beginning of southern wader migration.
The expedition was organised through the All Russian Institute for Nature Protection and took place in July and August 2016. The expedition members were Dmitri Dorofeev (RU) Alexander Matsyna (RU) Ric Elles (UK) Hazel Watson (UK) Peter Crighton (AU) and Robert Bush (AU).
I am grateful to Grace Maglio for assistance with assessment of feeding wader photos
In fact to be more precise, waders breed across a wide range of climatic zones from within the Arctic Circle, to sub-Arctic regions as well as well to the south. The vegetation at these different latitudes varies and so attracts different wader species that have species-specific preferences for different nesting environments. The north-western side of Kamchatka is a sub-Arctic region consisting of lowland tundra, remnants of Targa forest, coastal marshlands and tidal mudflats. The Long-toed Stint, Grey -tailed Tattler, Common Greenshank, Wood Sandpiper, Lesser Sandplover and Dunlin, among others, nest in these marshlands and the Far Eastern Curlew nests on the lowland tundra (see photos below).
Other wader species nest to the immediate north of Kamchatka in the Arctic and high Arctic but fly south after breeding to feed on these intertidal mudflats. The dominant species that breed directly to the north are Ruddy Turnstone, Red Neck Stint, Black and Bar-tailed Godwit and Great and Red Knot (see photos below).
After hatching, wader chicks are able to walk almost straight away; they can tolerate a wide range of temperatures and are also able to feed themselves. Parenting is limited to showing young the best and safest feeding areas and signalling danger from predators, such as approaching Raptors, Skuas and larger Gulls. These tasks are left to adult males with female adults usually departing the nesting area soon after hatching has taken place. Within two to three weeks males also leave the fledgling young to fend for themselves. Within a further two weeks or so the young leave the nesting area and fly to nearby intertidal feeding grounds.
This means that post breeding there is a continuous cycle of waders arriving on the intertidal mudflats over a period of about 10 weeks; first females and then a mix of females and males, then juveniles mixed in with these adults and eventually flocks that are predominantly young birds hatched a few weeks earlier. Despite a continuous flow of new arrivals on the mudflats, the population in the estuary remains constant at about 30,000 birds per day. This suggests that while there is a continuous flow of waders from the nesting grounds there is also a continuous number setting off on southern migration. On several evenings in any given week between 1000 and 10,000 waders leave the estuary.
Adult waders arriving at the intertidal mudflats behave differently to juveniles. Adults quickly occupy the productive feeding areas of the mudflats. Different species dominate different parts of the mudflats where their food preference is most abundant. Great Knots prefer molluscs (bivalves) on or near the surface of the central and south-western tidal zones. Black-tailed Godwits probe for polychaetes at what appeared to be the most abundant middle of the south-western mudflats. Eastern Curlew concentrated to the far end of the south-western edge of the intertidal zone. They mainly forage for burrowing prey such as crustaceans like crabs and shrimps. They use visual surface clues in the mud before probing. Looking downward to the mud surface and moving slowly they will then quickly probe deep into the mud, pulling out a crab, lifting their heads and swallowing. These abundant species tended to be in quite dense flocks, sometimes lifting together to move to other parts of the mudflats to feed. The density of the flocks probably indicates the specific areas of best food supply but also acts as some protection form predating Raptors and Skuas.
Juvenile Knots and Godwits arriving from the nesting grounds tended to join other juveniles to form small flocks (5 to 30) on the tundra close to the mudflats. They move onto the edge of the mudflats and if disturbed moved back onto the tundra. While they displayed their species specific feeding actions by probing (Godwits) and pecking and probing (Knots) or turning over small stones (Ruddy Turnstones) they did so in areas largely devoid of any abundant food supply. When they arrive they are inefficient feeders. After several days they joined up with adult flocks and began to feed more efficiently although remain on the edge of the flocks in what appeared to be the less food productive areas. Being on flock edges made them more prone to predation than the adult birds towards the centre.
Resighting of birds that had been caught and had small colour plastic tags attached to their legs for research purposes suggested that birds at this site could spend up to two weeks feeding before beginning southern migration.
Migration south occurred mainly in the evening. Migrating flocks tended to be dominated by the same species but it was also common to have smaller numbers of other waders join. So for example, flocks of Black-tailed Godwit set off with Common Greenshank mixed in at the edge of the flock. A common pattern was for a flock to lift off the mud surface rising 50 to 300 metres into the air and then to glide downwards again to settle on the mud. These ‘lifts’ would occur several times before eventually a flock would continue to climb, forming a rough V shape to head South West over the Sea of Okhotsk.
Mudflats and the surrounding tundra on the western side of Kamchatka provide a transition environment between nesting and migration for both adults and juveniles coming off the breeding grounds locally and for many waders that breed to the north. Both adults and juveniles feed and put on fat reserves here before migrating southward. While adults use existing knowledge and feeding skills to locate and exploit the most abundant food source zones of the mudflats, juveniles learn how to achieve efficient feeding through joining up with adult flocks.
The study of survival factors and rates needs exploration as climate change alters the synchronisation between breeding, food supply, migration timing and climatic conditions in this region.
What does seem apparent is the importance of these transition sites, like the Belogolovava River estuary in western Kamchatka, at the beginning of southern wader migration.
The expedition was organised through the All Russian Institute for Nature Protection and took place in July and August 2016. The expedition members were Dmitri Dorofeev (RU) Alexander Matsyna (RU) Ric Elles (UK) Hazel Watson (UK) Peter Crighton (AU) and Robert Bush (AU).
I am grateful to Grace Maglio for assistance with assessment of feeding wader photos