Migrant passage dates through Hong Kong are fairly predictable. If you are interested in the average arrival and departure dates in Hong Kong for some selected spring and autumn migrants, see here
http://www.geoffwelch46.com/AvgeMigrantDates1994-2014.xlsx
These are based on HKBWS records for the period 1994 to 2014.
The earliest spring migrant is easily Large Hawk Cuckoo, and the earliest autumn migrant is a close race between Asian (now Amur) Paradise Flycatcher and Eastern Crowned Warbler closely followed by Yellow-rumped Flycatcher.
The following graphs comparing annual average migrant dates with annual average spring temperature in Hong Kong may also be interesting
There appears to be a correlation between spring dates and average temperature - in a warmer spring, migrants arrive later and leave earlier.
Not perhaps surprising, but given that global warming is affecting HK temperatures (HKO data), it seems our spring migration is now coming later and finishing earlier.
The autumn graph is not conclusive
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Last edited by wgeoff at 8/01/2016 09:57 ]
