有關燕子的資料 Some information about Swallow and Swift

How are the survey sites decided for this study? It seems that there are very few in the Deep Bay area, although I think this is probably an important area for nesting Swallows. I'm sure other villages/estates hold larger numbers than some recorded in the "Top Ten" (e.g. San Tin, Kam Tin, Fairview Park, Palm Springs).
Also, are Red-rumped Swallow nests recorded as part of the survey? It could be useful to chart the colonisation of this species into Hong Kong.