Nesting Colonies of Vava'u's Outer Islands

posted by Kate Walker

Otu Motu Lalo outlined in red

In the early 1990s the three islands of Maninita, Taula and Lualoli (collectively known as Otu Motu Lalo) were proposed as a protected area by the Tongan government due to their importance as sea bird breeding colonies. Lack of resources and shifting priorities meant that this proposal was never taken any further. In the following years, Vava’u’s emerging eco-tourism market led to these islands being identified as potential tourist attractions and their importance was recognised by the New Zealand Overseas Development Administration funded Tongan Nature Tourism Program in 2002. As part of this program, a baseline survey of Maninita and Taula was commissioned and a rat eradication program was also carried out on both islands.

The baseline surveys, as reported by Dr D Watling from Environmental Consultants Fiji, list the species of flora and fauna that can be found on both islands and maps the ranges of vegetation habitat type. The dominant species of plant found on both islands is the tree locally known as Puko (Pisonia grandis), however their woodland type varies between islands. Maninita enjoys a high Puko tree forest with a solid unbroken canopy suggesting mature woodlands. Taula, on the other hand, is also mostly covered by Puko trees but the woodland is made up of shorter trees with a highly broken canopy. This difference is explained by the human use of Taula, where harvesting of seabird chicks is a known annual occurrence. There are plenty of signs of cut Puko trees which Watling accredits almost certainly to felling of trees to harvest the birds.

Typical coastal vegetation on Taula

The birds that were observed on Otu Motu Lalo are a combination of migrating species from the north and resident species of Tonga year round. During the two baseline studies, 21 species of birds were identified between the two islands. Of these species, three are resident breeding land birds (Wattled Honeyeater (Foulehaio carunculata; Fuleheu), the Banded Rail (Gallirallus philippensis; Veka) and the Collared Kingfisher (Todiramphus chloris; Sikota)), the rest are seabirds. Of the 21 species identified, five of them nest in these identified islands. The greatest abundance of nesting birds are the Black Noddy (Anous minutes; Ngongo)with an estimated 13,000 breeding pairs, next most abundant are the Brown Noddy (Anous stolidus; Ngongo) with an estimated 1500 nests across both islands and then the White Tern (Gygis alba; Tala) with an estimated 1,000 breeding pairs. 

Black Noddy (photo: 10000birds.com)

Brown Noddy (photo: 10000birds.com)

White Tern (photo: Dave Wiley)

 Red-footed Boobys (Sula sula; Ngutulei) also nest on both Maninita and Taula, but are found in higher numbers on Taula. It is thought that, unlike the noddys and terns, the boobys nest all year round and therefore the number of nests (approximately 50) found during the baseline surveys were not representative of the population size. This was further supported by the large number (compared to number of recorded nests) of Red-footed Boobys coming to roost, rather than nest, on both islands each evening or in high winds.

Red-footed Booby & Frigate Bird, Taula

 

Red-footed Booby over Taula

In addition to this, Taula hosts a breeding colony of Black Winged Petrel (Pterodroma nigripennis; Lafu). These birds nest in burrows up to one meter deep that they dig in sandy soil, visiting them late in the evening and at night. While Dr Watlings’ baseline survey was a comprehensive study of all flora and fauna species of the islands, he was unable to quantify the occupancy of the petrel nesting burrows. This is owing to a local village party that had visited the island a week before the survey and ‘devastated the colony’ through harvesting. It was felt by the survey team that additional disturbance of the nests would be detrimental to the health of any surviving birds. Therefore burrow numbers were used as an estimate of colony size and a figure of 200 petrels was derived.

Black Winged Petrel (photo: Nvoaden)

Petrel burrow on Taula (photo: D Watling)

  

The studies conducted by Dr Watling and his team show Maninita and Taula to be very important seabird nesting colonies with intact native flora. BirdLife International’s Important Bird Area proposal document states that these islands are some of the best remaining examples of Tonga’s small island ecosystems. However, the attributes that make them such important ecosystems are under threat from continued human exploitation and the lack of any management framework. 

Remains of a booby at a camp site on Taula

As well as being important nesting islands, the Otu Motu Lalo islands are also important nesting grounds for Vava’u’s marine turtle species and as such will be visited by the Vava’u Turtle Monitoring Program on an annual basis. We will be able to use this time to also monitor the seabird nesting population and human activity on these islands and look for any worrying trends that may emerge. 

 

Busy birds and stormy skies - large flocks of seabirds over the outer islands of Vava'u

 The first turtle surveys were completed during January 2013 and many eggs and chicks were observed on Taula with large flocks of seabirds being visible at all times. Seabird nesting was found on most of the outer islands visits, but without doubt, Maninita and Taula were the busiest. We have since made contact with Dr Watling and will be able to use his baseline data to compare any additional bird data that we collect.

Noddy egg in a nest on Taula

Very young noddy chick on Taula

Black Noddy chick getting close to fledgling on Taula

If you would like to find out more please contact us at info@vavauenvironment.org

Malo, Kate