The routes used by migrants observed passing Beidaihe

Martin  D.Williams

 Most migrants observed passing Beidaihe followed the trend of the coast—i.e. flew from the northeast towards the southwest. Many overflew the town, rather than fly around the roughly triangular headland Beidaihe occupies.
  La Touche (1914) also found that birds tended to follow the coast in the autumn: ‘The birds when bound south appear generally to follow the coastline, and many species may be observed by day, skirting the coast or passing overhead, either over Chingwangtao [= Qin-huangdao] or not far inland.’  Wilder (1924a) observed smaller birds ‘coming across the gulf [of Bohai]’, and suggests that: ‘Probably the migration route for them follows the China coast only approximately, cutting off the gulf by flights across rather than going around, as the waterfowl seem to do, so that their line of flight is southwest.’  He says La Touche also found that smaller birds crossed the gulf, yet it seems that La Touche only found this was the case in spring (La Touche 1914). From our observations, it seems that the birds arriving from across the gulf—which may include raptors, cranes and others, as well as passerines—may have only taken a short cut from near Shanhaiguan, over the sea to Beidaihe, rather than following the curve of the coast. Radar studies would help with determining routes of birds passing through the area—and show to what extent the migration is concentrated over Beidaihe.
  Shorebirds and terns were good examples of birds taking the short cut over Beidaihe. From observations at the Sandflats (few were seen from the Lotus Hills, as they passed too far to the east), it appeared they tended to pass down the coast to the Sandflats, then head over Beidaihe before continuing on down the coast.
  Cranes also mainly passed over Beidaihe, or even out over the sea. Some 3091 (65 per-cent) of the 4779 cranes for which routes were noted in 1986 passed to the east of the Lotus Hills (much to the frustration of the observers, since the highest Lotus Hill se-verely restricted views in this direction from the 1986 watchpoint). Though routes were not noted in later autumns, the majority of cranes again passed to the east of the watch-point. This contrasts with the spring, when it seems the tendency is for the birds to pass over the plain, perhaps accounting for Hem-mingsen’s autumn crane totals mostly well exceeding his spring totals. The larger flocks were especially prone to pass over the town or sea, perhaps as they were led by birds well used to travelling down the coast (smaller flocks, as they have fewer birds, are less likely to have ‘old hands’).
  By contrast to the cranes, the majority of Oriental White Storks passed over the plain inland of Beidaihe: 1565 (66 percent) of the 2358 birds for which routes were noted in 1986 passed to the west of the Lotus Hills. Black Storks showed an even higher ten-dency to pass over the plain; several flocks were seen well to the west of Beidaihe (ap-pearing distant even through telescopes): this may reflect the species’ liking for roosting in mountains as well as in lowland fields and wetlands, which are probably the preferred roosting habitats of the Oriental White Stork.
  Raptors also mainly passed over the plain, though their routes were perhaps affected more by wind direction than those of the above species. Northwest winds were usually the most productive for raptors, suggesting that the birds had been drifted eastwards from a more typical route to the west of Beidaihe. Further evidence for a more westerly route is provided by occasional observations at Shan-haiguan, ca. 30 km north of Beidaihe. Raptors—and Black Storks—have been noted passing in fair numbers over the mountains east of Shanhaiguan on days when little migration was evident at Beidaihe, or the weather conditions were much as on very quiet days for migration at Beidaihe (see ‘Visits to other localities’). There was per-haps a tendency for raptors to pass over the town and the Lotus Hills more in the morning than the afternoon, when the main route was over the plain: e.g. on 11 October 1988, when ca. 1100 Common Buzzards were logged, birds passed over the town and Lotus Hills in the morning, the route was roughly centred over the Lotus Hills by midday, and birds seen in mid afternoon were mostly passing well to the west. This may result from thermal developments during the day. So, presumably, does the tendency for raptors to be lower during early morning than around mid morning to early afternoon, when Pied Harri-ers, especially, were sometimes so high that they could only be detected with binoculars.
  Small passerines migrated over a broad front, overflying Beidaihe (the Sandflats was a good locality for recording early-morning passerine movements) and the plain, though there were no records of any numbers pass-ing over the sea east of town. As with several other birds, it appeared there was a tendency for them to arrive from over the sea to the east of town, and fly westwards or southwest-wards overland. This may reflect the use of the Beidaihe headland, and especially the Lo-tus Hills, as landmarks in an otherwise flat coastline. As noted above, the rocky outcrop at the Lotus Hills may be a better watchpoint for recording actively-migrating small pas-serines than the southeastern hill. The passerine migration on a given day may not be over a broad front, and there may be great differences in numbers recorded at different localities. Good examples are 11 October 1988, when 2715 Penduline Tits Remiz pen-dulinus were recorded from Daihe, yet only 50 from the Lotus Hills, and 13 October 1988, when 4500 Northern Skylarks Alauda arvensis were recorded from Daihe, and only 144 from the Lotus Hills. The wind was force four to five on both these days, northwest to west on 11th and westerly on 13 October, and the birds may have been flying low as a result (substantial numbers of actively migrating small passerines have been recorded from the Lotus Hills on other days).