Friday, 11 December 2015

Small terns on the Gippsland Lakes

Australia has two species of very small terns, Little (Western Pacific Little Tern Sternula albifrons sinensis) and Fairy (Australian Fairy Tern Sternula nereis nereis). In length the small terns fall between a Willie Wagtail and the slightly larger Rainbow Bee-eater. Both species inhabit coastal areas including ocean beaches, coastal lagoons and lakes (such as the Gippsland Lakes) and estuaries.

Click on images to enlarge.

Adult Little Tern in breeding plumage, note key ID features - dark tip to yellow bill, black lore, white over eye and dark primary flight feathers.

Both species are very similar in appearance and habits, making identification in the field difficult even for adult birds in breeding plumage when there are some distinctive features that help separate the two species. In non breeding and eclipse plumage, identification is nearly impossible.

Adult Fairy Tern in breeding plumage, note key ID features - all yellow bill, white lore, no white over eye and grey primary flight feathers.

The two species largely occupy separate sections of the Australian coast with Fairy Terns found along the south and west coasts and Little Terns found along the east and north coast. This can be helpful for field identification in locations where one species or the other is mainly found. However, there is overlap, particular in eastern Victoria including the Gippsland Lakes, where both species are regularly found and where both species breed.

But for birders on the Gippsland Lakes small tern identification can be a challenge especially at a distance. Adding to the challenge is the fact that non-breeding Little Terns from the Asian population overwinter in Australia. Records of banded birds have shown that birds that have bred in Japan appear on the Gippsland Lakes during our summer, though these birds are never in breeding plumage. It is also suspected that Little and Fairy Terns have interbred, giving rise to hybrid birds. This may also be contributing to the identification challenge of these small terns.

I was recently privileged to make two visits to Crescent island on the Gippsland Lakes south of Paynesville where a breeding colony of Fairy and Little Terns has been established on a recently dredged sand spit. The project to restore the integrity of Crescent Island was a multi- government effort initiated by Bairnsdale based Faye Bedford – Biodiversity Officer, Regional Services, Department of Environment, Land, Water and Planning. This is a good news win-win story where channels have been deepened for boats and habitat created and enhanced for threatened species such as Fairy and Little Terns (Fairy Terns are listed as Endangered and Little Terns as Vulnerable in Victoria).

Our transport to Crescent Island - a great way to travel on the Lakes.

Unfortunately for small terns and many other beach nesting birds their preferred sandy beach habitat is also often ideal for human recreational activities. To protect these birds, especially during their critical breeding season, which also coincides with our peak use of beaches, exclusion signage and sometimes fencing is required.

Conducting a survey of the small tern breeding colony at the eastern end of Crescent Island.

Erecting signs at the breeding colony.

About a dozen signs were erected at intervals along the shoreline.

Even with the utmost care it is impossible when visiting a small tern breeding colony to not disturb the birds so our time there was necessarily limited by consideration for the welfare of the birds and their chicks. We kept to the margins of the breeding area to minimise disturbance and to avoid inadvertently treading on eggs which are well camouflaged and therefore very hard to see on nests that are mere scraped depressions in the sand and shell grit.

The following selection of photos captures both species of terns including some birds at nests with chicks.

Little Tern in streamlined flight.

Little Tern showing the dark primary flight feathers - tail fanned.

Little Tern on nest scrape. Little Terns commence breeding a few weeks after the Fairy Terns.

Fairy Tern with small fish to feed a chick.

This tern has some black on lore and dark wing feathers however its bill is all yellow - not sure if this is a Fairy or Little Tern?
Fairy Tern in flight clearly showing all yellow bill, white lore and pale grey primary flight feathers.

Another view of an adult Fairy Tern.

A pair of Fairy Tern chicks - they are obviously very vulnerable at this stage and completely dependent on their parents for protection and food.
Fairy Tern parent on nest with chick. Note the bill still has a small dark tip.

This Little Tern has returned to breeding colony with a fish however it is not clear that the fish is for this chick which given the earlier start to breeding by the Fairy Terns is probably a Fairy Tern chick.
Fairy Tern hovering - both small tern species hover more than other tern species. They often hover to size up fish before diving head first into the water to catch them.
Another view of a Fairy Tern hovering - note the elegant swallow tail.
Adult Little Tern commencing the transition to breeding plumage - note yellowish base to bill. Some primary flight feathers are also moulting.
This shot of an adult Little Tern shows how long their wings are for such a small bird. This bird has a band.
This Fairy Tern also has a band which may help piece together the lives of these terns which are still far from fully understood, especially their movements outside of the breeding season.

The small terns seem so fragile - continued human population growth and development plus sea level rise is a growing threat to their habitat – let’s hope we can wisely manage their environment and assure a future for them.

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