Juvenile tern ID?

On a recent boat trip to Crescent Island in the Gippsland Lakes National Park south of Paynesville to check on the Pelican breeding rookery, we found a lone – no adults present -small juvenile tern which we could not identify there and then in the field. We could see it was neither a Fairy or Little Tern which we are very familiar with given we have been monitoring their breeding colonies on the Gippsland Lakes for over five years now. 

Please click on photos to enlarge.

A small juvenile tern on a sand spit caught our attention – but what species was it?

This photo gives a size comparison with a Silver Gull and Black Swan.

The bird had distinctive red legs and some red in the bill which was potentially an ID guide, however the Morcombe and P&K guides we had on our smart phones were no help as they either did not show juvenile legs on terns or where they did for possible contenders they showed black legs. Given the mottled plumage was the fledging feathers this bird must have been no older than 6 months in which case it was raised during the summer breeding season just passed. So that ruled out species such as White-winged Black Terns which breed in the northern hemisphere – only locally breeding tern species would be possible.

Fortunately the juvenile bird was very obliging as it preened allowing us to approach closely by boat and get some good photos for later ID at home with access to other guides. Until then we had to contain our excitement that we may have found a rarity in our patch.

The small tern preened as we approached.

The bird was briefly disturbed by other much larger species on the sand spit giving an opportunity for a flight photo showing wing and tail feathers to assist with ID before it quickly settled back on the spit and continued preening. Like many young birds this juvenile tern appeared to be a little naïve making it vulnerable to predators.  

Once home I consulted the Australian Bird Guide by Menkhorst et al, which in my opinion is currently the best field guide available, especially with respect to juvenile species. That said we are spoilt for excellent bird field guides in Australia such as the Slater, Simpson & Day, Pizzey and Morcombe guides – I have copies of them all and regularly consult these guides. 

It soon became apparent the juvenile small tern in question was a Whiskered Tern. The presence of Whiskered Terns in East Gippsland is rather sporadic depending on seasonal conditions however they are frequent visitors and do breed in our area – so our mystery juvenile tern was not a rarity as hoped for and while a Whiskered Tern was somewhat of an anticlimax in this case the following photos show it to be a beautiful small tern which I was happy to have photographed.

For photos of adult Whiskered Terns and information regarding an East Gippsland breeding event please see the following Avithera post: http://avithera.blogspot.com/2017/01/whiskered-tern-breeding-colony-lake.html

As this example shows, modern digital cameras have become an essential birding tool as they greatly enhance identification of bird species.