A Black-headed Bunting turned up after a long absence. It was very likely the same individual I briefly glimpsed in the same paddy field about a week ago. It was mixed in with a flock of several hundred Eurasian Tree Sparrows.

A Forest Wagtail appeared on the usual forest road — the sixth individual this season. Arriving this late in the year, there is a good chance it will winter here. Last year one wintered at the same spot. Once they settle into wintering mode, though, they tend to stay deep inside the forest and become harder to observe.

Arctic Warblers have been showing up since early October. Birds fresh in from migration are often in small flocks, but now they have spread across the island and each is holding a small territory. Many individuals will stay through to spring. Come April, they form flocks again in preparation for the northward journey, and some begin to sing.

Brambling have also appeared. They joined up with Eurasian Tree Sparrow flocks and were feeding on second-crop rice grain in the paddies.

White-shouldered Starlings — a few birds — were mixed into a flock of several tens of White-cheeked Starlings, along with around 20 Common Starlings. The wintering White-shouldered Starling population on the island is sizeable in its own right, and flocks of several tens are regularly seen in parks and the like.

At this time of year, snipe are mostly Common Snipe, but among a flock of ten-odd I found just two Swinhoe's Snipe. I expect them to disappear once the second-crop rice harvest gets under way. Other waders lingering in the paddies include Common Redshank, Common Greenshank, Marsh Sandpiper, Black-winged Stilt, Wood Sandpiper, Green Sandpiper, Common Sandpiper, and Long-toed Stint.

Ducks are increasing too — I recorded my first Mallard of the season on Ishigaki. Mallard used to be quite scarce on Ishigaki and Okinawa, but the numbers being seen seem to grow a little more each year.

A Crested Serpent Eagle was eating a toxic Cane Toad. Below I reproduce the article I wrote on Crested Serpent Eagle venom resistance, published in the newspaper on 19 July.

Crested Serpent Eagle's Hidden Ability — A Remarkable Coincidence

The Crested Serpent Eagle, found in Japan only on Ishigaki and Iriomote islands, is known to prey on the toxic Cane Toad. A research team led by Arisa Tobe of Kyoto University has used genetic analysis to show that the eagle may carry resistance to the toad's venom. The birds have harboured a venom-resistance gene mutation for tens of thousands — possibly hundreds of thousands — of years, meaning the "hidden ability" was already in place long before Cane Toads were introduced to Ishigaki Island. The findings were published on 14 July in the scientific journal BMC Ecology and Evolution.

No Symptoms

Cane Toads were introduced to Ishigaki Island around 1978 to control sugarcane pests. They secrete a potent cardiotoxic steroid, bufadienolide, from their skin — a toxin that can stop the heart. There are confirmed cases of the native Sakishima Rat Snake dying after eating one. The Crested Serpent Eagle, on the other hand, shows no ill effects even after consuming the toad's highly toxic skin. Local birdwatchers had long noticed this, but no scientific explanation had been established.

A Gene Mutation?

The research team analysed tissue samples from 24 Crested Serpent Eagles that had died from accidents or illness between 2020 and 2023. Focusing on an enzyme responsible for ion transport across cell membranes — the target of the toxin — they discovered an amino-acid substitution in a key region associated with venom resistance, known as the Q111E mutation. This mutation appears to prevent the toad's toxin from binding to the enzyme, neutralising its effects. Similar mutations have been found in snakes that prey on toads and in birds that eat toxic butterflies, and the finding is regarded as an example of convergent evolution — the process by which unrelated lineages independently arrive at similar traits through different evolutionary paths in different places.

An Ancient Defence

Strikingly, Crested Serpent Eagles on Iriomote Island — where Cane Toads have not established — and even a subspecies of Crested Serpent Eagle on the distant Indonesian island of Simeulue carry the same resistance gene. Genetic analysis suggests the trait has been preserved since around the time the Crested Serpent Eagle diverged as a species, long before any alien species was introduced. Tobe of Kyoto University's Wildlife Research Center explains: "The venom resistance of the Crested Serpent Eagle is not a recent adaptation to environmental change, but an ancient trait inherited from its ancestors — one that has, by coincidence, also helped to mitigate the physiological impact of an invasive species. It is a rare example of that."

Other Raptors Too

The study also confirmed similar resistance gene mutations in snake eagles closely related to the Crested Serpent Eagle. There are reports that the Black-chested Snake Eagle in South Africa showed no health problems after being fed toxic toads in captivity for 12 months, suggesting this ability may be characteristic of the group as a whole. Meanwhile, on Japan's Ogasawara Islands, Eastern Buzzards have been recorded preying on the same Cane Toad, but no clear venom-resistance mutation was found in their genes, pointing to the possibility that they cope through a different mechanism.

A New Perspective for Conservation

The study also found that the Crested Serpent Eagle populations on Ishigaki and Iriomote islands are genetically distinct. Despite a separation of only about 20 kilometres, movement of individuals between the two islands appears to be almost nonexistent — a finding the team says "suggests that the Iriomote and Ishigaki populations should be considered independent conservation units." The research demonstrates that an organism's "hidden abilities" may play an important role in responding to environmental change. While the findings offer a significant new perspective for biodiversity conservation, Tobe also sounds a note of caution: "The fact that the eagle is making use of the invasive species does not mean the invasive species problem can be ignored. Once the Crested Serpent Eagle is preying on them, the toads are being incorporated into the ecosystem, and there is a risk of further disrupting the overall balance." As the global impact of invasive species on ecosystems becomes an ever greater concern, this discovery — shining a light on the unexpected adaptive capacity of native species — underscores both the depth of evolutionary processes and the complexity of conservation strategy.