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An interesting article in the CBN just out
CBN 30(4)141-145, about Little Eagle decline, provides
evidence of reduced breeding by the species locally. That may well be so and I
would not doubt it. It is concerning. However it mentions a comparison with
GBS data that supposedly doesn't support the same conclusion. I hasten to point
out that they are measuring different things. Reported abundance, as surveyed in
the GBS, can increase when suburbs encroach on or come closer to former nesting
sites of the species. The species can still be present in the area but suffer
reduced breeding. Indeed if they are spending less time at a nest, then they may
well be spending more time flying over the suburbs and so be seen more often by
GBS observers. So I don't see the results as conflicting at all. Indeed I
suggest that is what has happened. For a species that may live for many years,
there will easily be a delayed effect in breeding but not in presence. It is
disappointing to see the GBS data mentioned as data not in harmony, when this
approach was not at all necessary without explaining how the two sets of
information fit together. Besides the GBS Report only summarised what the data
shows.
As for the suggestion of misidentification, I
don't agree at all. It can be argued that almost any bird in any survey can
be misidentified but that is hardly helpful. In practise it is hard to confuse a
Little Eagle for anything else locally, apart from a Whistling Kite and Black
Kite. People would not record an ID on the GBS of something as different as the
other species mentioned, if they are that unsure. The culture of the GBS has
always been to be confident of the accuracy of your ID. In any case, it is
obvious from the figures given in the report that the numbers of GBS
observations of the Whistling Kites and Black Kites are so low, that even if
every single Whistling Kite and Black Kite GBS record in the history of the GBS
was in fact a Little Eagle (or indeed real Whistling Kites and Black Kites
recorded as Little Eagles), then the quantitative difference would be so
low it would barely impact on the statistics for the much more common
Little Eagle. Besides the misidentification issue only arises on assessing
trends, if relative rates of misidentification have changed over the years,
(in particular in this case increased). I doubt it. With the increased
number and availability of several good field guides and things like the couple
of Raptor ID workshops that COG has run over the years (to which Jerry Olsen,
myself and others contributed), identification accuracy rates should have
improved since 1981, not decreased. This is another factor consistent with the
slight suggestion of increased status for the Little Eagle in the GBS (more
people able to identify them). However it is not at all inconsistent with a
reduced breeding status of the species. Fair opinion that in the long term that
is what is important.
Philip
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