In response to variations in weather (ranging from drought
to violent storms) or vegetation, species that move might appear in a given
locality once every (for example) 3, 10, or 30 years, or at wider intervals.
Range diagrams follow reports of occurrence. They also
involve interpretation of occurrences. Consider Hanzab and the Schodde/Mason
‘Directory of Australian Birds’:
H shows the range of the Little Wattlebird as encompassing
Canberra; D has the western limit on the eastern side of Braidwood.
D shows the range of the Black-chinned Honeyeater as brushing the western
border of the ACT; H shows it as ending about 70km to the west of
that. Both show the ‘exceptional’ range of the White-fronted
Honeyeater as extending east to about Wagga, about 150 km in a straight line
from the ACT.
Thanks to all who responded to the survey questions. We
do not know what the history of occurrence of either of those species might
have been. We only know, perhaps incompletely, the reported occurrences.
Essentially, the questions were about the likelihood of the
species occurring and not being reported in the specified area. In
thinking about this, a great many considerations come to mind, some of which
have been mentioned on the list, or were to me directly. There is no right
answer, so it comes down to individual perceptions.
Two elements were tightly specified, time and area.
Others were loose: ‘probably’ ( I take to mean more likely
than not), ‘several’ (I take to mean 3 or more), ‘visited’
and ‘times’(I take incursions by separate groups or
ungrouped birds in one year to be separate visits). It doesn’t
matter if others interpreted those expressions differently.
Perceptions were markedly different for each species.
Assigning slightly veiled responses to one side or the other, and adding my own
view, the results were:
Black-chinned: overlooked 11, not here 4
White-fronted: overlooked 4, not here 9, no answer 2
An interesting question is whether the authors of those
range diagrams will now redraw them. It is a matter of interpretation of
the ACT reports, to which the author’s own answers to the survey
questions might be relevant.
I shall leave it there. I shall not repeat the
exercise for the Square-tailed Kite.
