Differences in Detectability of Red Kites and Honey Buzzards
Red Kites are on site (or at least in the vicinity of their breeding areas) all year. They have been released in particular areas and are often obvious on a surveyor's arrival. Dedicated surveyors monitor their locations and behaviour in at least some of the release areas.
Honey Buzzards are summer visitors, migrating freely over long distances to any locality and are very secretive in their habits. Further Honey Buzzards nest in heavily wooded, often remote, areas which are very difficult to work and there is very little experience in searching for the species in the UK. To find a pair you need to have some confidence that the large amount of time spent is going to be rewarded and from what I have heard about the official survey this year this has not happened everywhere.
There is also the identification problem. A forest
ranger or gamekeeper would quickly identify a Red Kite and tell local
field workers; they would probably not identify a Honey Buzzard from
a Common Buzzard so no news would be forthcoming. Many field workers
in large difficult areas do get considerable help on conspicuous
species from estate workers. It needs to be appreciated that many
inland forest areas in northern Britain are very little visited by
birdwatchers particularly after spring.
Further it is not even clear that all field workers would actually pick up a Honey Buzzard in its breeding area. A number of birders this year have pointed out how they have mastered Honey Buzzard identification having seen some reasonable numbers at last. No experience with identification of a species can mean it is overlooked.
[Based on a reply to J. G. Cracknell on UKBN]
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