We’re away, home again in September

Wednesday 14 April 2021 | Written by Gerald McCormack | Published in Features, In Depth


We’re away, home again in September
Plover in breeding plumage ready for an April departure to Alaska. Gerald McCormack/21041303

The Pacific Golden Plover or Tōrea is our most common Alaskan migrant. It is conspicuous on large grassy areas during the summer and most are now in their dramatic breeding plumage and ready to depart for Alaska. By Gerald McCormack of Natural Heritage Trust.

Cook Islands Tōrea

During our summer, the dull brown Tōrea or Pacific Golden Plovers are common and widely spaced on grassy areas. They are very territorial and act aggressively towards any intruding plover. Each year they typically return to the same territory. If an earlier arrival has moved in, a serious dispute ensues, which is usually won by the original owner.

Plovers typically stand motionless in an upright posture on one leg and intermittently jog a few paces before standing still again. They are watching for small invertebrates in the grass which they grab with their beaks and immediately swallow.

When disturbed they take flight often giving their “tuuu-ree.....tuuu-ree” alarm call, which is the basis of their local names Tōrea (Rarotonga, Mangaia, Aitutaki, Manihiki, Rakahanga and Penrhyn), Toretōrea (Ātiu, Ma‘uke and Miti‘āro) and Tuli (Pukapuka and Nassau). Elsewhere in Eastern Polynesia they are known as Tōrea or a cognate: Tōrea in the Societies and Tuamotu, To‘ea in the Marquesas with their missing “r”, and Kōlea in Hawai‘i with their “k” for “t” and “l” for “r”.

Take care with Aotearoa Māori because they transferred Tōrea to two species of oystercatcher and then, not seeing any Wandering Tattlers, they applied the tattler’s tropical Polynesian name Kuriri to their Pacific Golden Plover.

In Western Polynesia the plover is Tuli on Samoa, Tuvalu and Tokelau – as it is in nearby Pukapuka, while Tonga and Niue are unusual in using the name Kiu. The Samoan and Tongan names also include the Wandering Tattler.

The Trust studied the Tōrea on Rarotonga Airport 1994-1997 and concluded they left in large groups during the first two weeks of April and most returned in September-October. In those days there were about 130 birds within the airport in the late afternoon, consisting of the permanent residents of the grassed areas and the early arrivals from elsewhere on the island to take refuge on the runway to avoid nocturnal predators. Fewer plovers have been reported on the Airport in recent years and also in various overseas locations, such as New Zealand, which might indicate a general decline of the species.

Hawaiian Kōlea

The Kōlea on Oahu in Hawai‘i have long been popular with researchers. It was well-known that plovers returned to the same territories on Oahu each year. In the 1990s Oahu plovers with radio transmitters were found breeding in southwest Alaska. There was also evidence that male birds returned to previous breeding sites while female found new mates.

In April 2009 and 2010, Oscar (Wally) Johnson and his team attached geolocators to 20 Oahu plovers. When some of the locators were retrieved from birds returning in August, the data showed they had flown northward direct to Alaska and after breeding they fed near the southern coast before flying directly back to their territories on Oahu. They did each 4000km trans-oceanic flight non-stop in 3-4 days (see map).

Most researchers assumed South Pacific plovers also undertook direct Alaskan flights in what they called the mid-Pacific Flyway.

Migration routes established since 2009 using various sorts of attached trackers. The discovery of the northward route via Japan was discovered in 2010 with plovers in Samoa. In 2020 it was shown that Mo‘orea plovers take the same clockwise route. Gerald McCormack/21041304

American Samoan Tuli

The mid-Pacific Flyway theory was tested in March 2010 when the Johnson team put geolocators on 19 plovers on Tutuila in American Samoa. They retrieved the locators from 10 returnees in August-September and what a surprise they got.

The data showed the ten birds flew mainly non-stop 7500km to Japan where they feed around the rice fields for about three weeks. They then flew 5000km to western Alaska to breed, generally north of the Hawaiian plovers. After breeding, they fattened themselves near the coast before they flew non-stop or with only very short breaks on intervening islands back to their territories on Tutuila (see map).

Although it was amazing to discover that Samoan plovers flew to Japan before Alaska, the question remains: do the more eastern plovers from the Cook Islands and French Polynesian also fly to Japan?

French Polynesian Tōrea

In 2017 and 2018 the Johnson team put satellite trackers on 20 Tōrea on Mo‘orea, which is 9500km from Japan and 8500km from Alaska, with Hawai‘i as an ideal mid-way stopover.

Despite the high hopes for lots of real-time data via satellite, the equipment proved troublesome. Nevertheless, the data showed that 13 departed to the northwest and ten arrived in Japan with most having had non-stop flights. Nine birds left Japan and although it was expected they would all go to western Alaska, four went to Siberia to breed. It would be interesting to know if Cook Islands Tōrea go to both Siberia and Alaska.

The researchers tracked only two birds leaving Alaska. One was lost north of Hawai‘i, while the other flew in eight days 8500km to Samoa where transmission ceased two weeks later. Neither this bird nor any other of the colour-banded birds have been found on Mo‘orea. Given the normal high survival rate of migrating plovers it is unlikely many died en route. The researchers suggest that they might have stayed or taken long stop-overs on other islands; or, they were not site-faithful on Mo‘orea and therefore not found.

The research on Mo‘orea is ongoing and its results will be a good proxy for the migratory behaviour of Cook Islands plovers.

More detailed research information is available on the Trust’s blog at http://www.cinature.org/.