September 18th – Up Against The Wall

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Although many kilometers away across the steppe, the Tien Shan Mountains impose an impassable wall for migrating birds.
Although many kilometers away across the steppe, the Tien Shan Mountains impose an impassable wall for migrating birds.

Millions of birds breed in the taiga of Siberia and eastern Europe or in the vast steppe country of central Asia. Most of them spend the Winter in India/southeast Asia or sub-Saharan Africa. A direct flight from breeding to wintering ground would be a feat in itself but these birds have an added obstruction to deal with – the extensive mountain ranges that run for thousands of miles across their migratory pathways: the Himalayas, the Hindu Kush, and the Tien Shan Mountains (Celestial Mountains).
I was standing at 11,000 feet when I took this shot; the peaks soar thousands of feet above me yet.
I was standing at 11,000 feet when I took this shot; the peaks soar thousands of feet above me yet.

The mountains are bleak and barren providing little cover (or nourishment) for migrating birds.
The mountains are bleak and barren providing little cover (or nourishment) for migrating birds.

A group of 5 of us (Peter Thoem, David Brewer, David Lamble, Larry Hubble and myself) travelled to Kazakhstan at the beginning of September to participate at a banding station in the Tien Shan Mountains – Chokpak Ornithological Station. Chokpak is situated about 530 km west of Almaty, the major city of the country, and is nestled up against the foot of the mountains, which run east/west. A ridge of low hills running north/south comes in from the north. Birds tend not to go over high mountains and so these two topographical features tend to funnel migrating birds through a pass where they meet – Chokpak. When birds move south and are confronted by the Tien Shan they head west along their foot until the mountains either end or bend to the south.
Chokpak Hill looking west - see the curve in the mountain ridge in the distance.
Chokpak Hill looking west – see the curve in the mountain ridge in the distance.

Chokpak Hill looking east. Note the ridge of hills running in from the left (north). Also note the line of trees/scrub running east/west.
Chokpak Hill looking east. Note the ridge of hills running in from the left (north). Also note the line of trees/scrub running east/west.

At Chokpak, looking south toward the Tien Shan Mountains - a solid wall barring the way of small migrants.
At Chokpak, looking south toward the Tien Shan Mountains – a solid wall barring the way of small migrants.

At Chokpak there is a relatively low hill that the birds must go over. The scientists studying these migrants have placed a large Heligoland trap at the top of the hill to capture them. A Heligoland trap is like a long mesh funnel that birds enter unknowingly; the flight space gets smaller and smaller until, near the end, it is only a couple of meters wide/high. At this point there is an “exit” – a plexiglass sheet that they think is an opening out – they bump against it and slide down into a collecting box. These boxes are interchangeable: when one is full it can be slid out and another put in its place.

The "mouth" of the huge Heligoland - a long mesh funnel.
The “mouth” of the huge Heligoland – a long mesh funnel.

In the mouth of the Heligoland looking west - the little white patch at the back is the entrance to the collecting box.
In the mouth of the Heligoland looking west – the little white patch at the back is the entrance to the collecting box.

The main factor determining whether birds are caught or not is the wind: if it is out of the east (a tail wind for autumn migrants) then the birds fly high over the trap. But if it is out of the west (a headwind), then they tend to stay low seeking shelter from it and enter the trap.
Birds fluttering around the entrance to the collecting box - the white square is an opaque piece of plexiglass that lure the birds into the box; they bump against the glass and then slide down into a holding box. Net baffles extending from the sides prevent birds from going back out of the trap.
Birds fluttering around the entrance to the collecting box – the white square is an opaque piece of plexiglass that lure the birds into the box; they bump against the glass and then slide down into a holding box. Net baffles extending from the sides prevent birds from going back out of the trap.

Most birds banded are caught in the Heligoland trap but we also ran 8 mist nets set out in lanes cut in the scrubby forest at the base of the hill. These nets tended to catch species that would not be caught in the larger trap (e.g., various small warbler species).
One of several mist net lanes we cut into the scrub. These nets caught birds that weren't often caught in the Heligoland trap.
One of several mist net lanes we cut into the scrub. These nets caught birds that weren’t often caught in the Heligoland trap.

In the early days (the station was formed in 1966), there were 3 Heligoland traps on the go at one time – all side by side. Now, with manpower restrictions they are able to run only one. Still it is not unusual to get 1-2,000 birds on a good day!
Red eye indicates that this is an adult European Bee-eater. Bee-eaters migrate in large flocks over open country and are often caught in good numbers in the Heligoland.
Red eye indicates that this is an adult European Bee-eater. Bee-eaters migrate in large flocks over open country and are often caught in good numbers in the Heligoland.

Orange feathers in the secondary coverts indicate a male bird.
Orange feathers in the secondary coverts indicate a male bird.

Young (brown-eyed) European Bee-eater.
Young (brown-eyed) European Bee-eater.

Rick

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