Hello Birding-Ausers,
I have noted that there are reports of recent Sooty Tern sightings from
Sandgate (a northern suburb of Brisbane, Queensland, Australia) and Redcliffe (a
city of some significance just north of Brisbane and across the bay from
Sandgate) listed on the Birds Queensland Birdline (managed by Julian Bielewicz).
As I live in Redcliffe the reports from there are of interest to me.
However a check of the field guides and The Handbook of Australian, New Zealand
and Antarctic Birds (HANZAB), Vol 3 to remind me of the diagnostic features (I
don't see Sooty Terns every day) produced an anomaly.......the overall length
(OL) measurement.
The following publications describe the OL (of Sooty Tern) as (from) 40 cm to 46
cm:
-The Field Guide to the Birds of Australia, Pizzey and Knight;
-Field Guide to the Birds of Australia, Simpson and Day;
-The Slater Field Guide to Australian Birds, Slater, Slater, Slater;
-Readers Digest Photographic Field Guide Birds of Australia, The Australian
Museum, Flegg, Longmore;
-Seabirds an Identification Guide, Harrison;
-The Shorebirds of Australian, The National Photographic Index Of Australian
Wildlife, Pringle;
-Readers Digest Complete Book of Australian Birds.
Whereas, the following publications describe the OL as 33 cm to 36 cm:
-HANZAB Vol 3, Higgins, Davies;
-Field Guide to Australian Birds, Morcombe.
It is interesting that the publications claiming the larger measurements are
'older' ones and were published 'pre-HANZAB'.
Morcombe has obviously been guided by HANZAB.
Which is the correct measurement?
I feel that this is an important point as a difference of approx 10 cm is
equivalent to a complete 'size' change.
I would say that the terns seen in Australia roughly fall into the following
size ranges:
Small: 20 to 29 cms
Medium: 30 to 39 cms
Large: 40 to 49 cms
Very large: 50 to 59 cms
Note: this is a rough guide only as there is some overlap in some species.
A size range of 40 to 46 cms would make Sooty Tern similar in size to Crested
Tern and larger, on average, than Lesser Crested and Gull-billed Terns and the
Noddies.
However, a size range of 33 to 36 cms would make Sooty Tern similar in size to
Common, Arctic and Roseate Terns.
An interesting aspect of the information on dimensions provided in HANZAB for
each species is that there is much attention paid to most parts of the bird
other than the overall length!
Why is this? (or am I missing something in the text of HANZAB?)
This is often the only measurement given in field guides and I am sure that it
is a feature used by many birdwatchers in their identification process.
I must say at this point that I have seen Sooty Terns previously and it would be
hard to confuse adults with the other species mentioned above.
However, the ones I saw were not, from memory, standing beside any of those
other species and so I could not say how they compared precisely for size.
It is tempting to assume that the older texts are the correct ones as they are
in the majority.
However, more than once before authors of field guides have fallen into the trap
of accepting someone else's claims only to find out later that the information
was wrong and was, in fact, based on assumptions and not actual observations.
I am inclined to think that HANZAB is correct; I would hate to think that such a
monumental publication would contain simple errors such as this.
But HANZAB does suggest (when describing species similar to Sooty Tern) that the
Noddies are
slightly smaller than Sooty Tern; at 33 to 36 cms (HANZAB's figures), the only
Noddy smaller than
Sooty Tern would be Lesser Noddy! A bit worrying!
Any comments?
Bob Inglis
Woody Point, SEQld, Australia.
27 deg 15min S; 153 deg 5 min E
E-mail:
Home Page: http://www.powerup.com.au/~inglisrc
Mystery Bird Page: http://www.powerup.com.au/~inglisrc/mystery_bird.htm
Regent Honeyeater Page: http://www.powerup.com.au/~inglisrc/page013.htm
Camcorder Page: http://www.powerup.com.au/~inglisrc/camcorder_intro.htm
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
To unsubscribe from this mailing list, send the message
"unsubscribe birding-aus" (no quotes, no Subject line)
to
|
