Last week I gave you this bird to have a go at identifying:
I thought that some of you would find it quite easy and I wasn’t wrong, although it’s not quite as straightforward as I thought.
Our regular ornithology expert Wouter van Gestel was straight in with an interesting answer that highlights some of the idiosyncrasies of museum specimens, where the colour of features like bills and legs can fade after death. This can make identifications tricky, since colour can play an important role in distinguishing between species in the same genus. In addition, the maturity of the animal can also complicate identifications, since juveniles can have different colours and markings to adults.
That makes this specimen doubly hard to identify and jennifermacaire pointed out an additional idiosyncrasy – the glass eye used by the taxidermist. The choice of eye is an important one, since eyes play an important role in making something look as it did when it was alive. In this case I think they used an eye that was too large with too much iris showing.
Both Wouter and Jennifer identified this as a Tropicbird, and both thought it was the White-tailed species. However, according to the Museum database the specimen is a young Red-billed Tropicbird Phaeton aethereus Linnaeus, 1758.
Now I’m going to check the identification again, since it isn’t unusual for specimens to be misidentified. This is a problem in museums, since specimens come from all sorts of sources and not all of them are necessarily expert.
I recently had to check the identification of a couple of Tern specimens from Jamaica for an enquiry. If the specimens had been the species they were originally recorded as, it would have been the only record of the species on Jamaica and it may have hinted at a lost population. In the end it was a simple misidentification of a common species.
This is part of the reason why specimens in museums are so important – they provide a primary record that can be checked to ensure information about biodiversity is correct, so we can understand things like changes in population distribution with confidence.
If you want to check the ID of this mounted bird then have a look at this article which contains a comparision of the biometry of red-billed and white-tailed tropic birds: file:///C:/Users/Eigenaar/Downloads/2013_SexdiscriminationinTropicbirds.pdf
Red-billed tropicbirds are larger and have a longer bill than white-tailed, as you also can see on the website of my late friend Edward Soldaat, who put the skulls of these species side by side:
That link did not come through completely, so I’ll give you the data on culmen lenght from that article:
Red-billed male: 63.20 +/- 2.26 mm female: 61.06 +/- 2.15 mm
White-tailed male: 47,64 +/- 2.21 mm, female: 48.11 =/- 2.11 mm
These avarages were based on resp. 71, 68, 31 and 26 individuals
Brilliant – thanks Wouter!
Will you let us know what your final ID of this bird will be?
Fascinating! Thanks, Paolo and Wouter.
So, in this case, the eyes DON’T have it.