Variation in the Heartbeat of the White Tern <i>Gygis alba</i> during Incubation

Rapid global heating is a particular danger to tropical birds already near their thermal maximum. White Terns Gygis alba are important to tourism in the Seychelles Islands, where, in 1974, we took an unexpected opportunity to measure the heart rate of two incubating adults. We found that the birds had higher heart rates at night compared to during the day, and their heart rates increased rapidly when approached by people. Local temperatures have risen considerably since these data were collected nearly 50 years ago and are predicted to rise even further by 2100. Given the importance of White Terns as a resource for ecotourism, and the likelihood that they will move closer to their thermal maxima as climates warm, an urgent re-evaluation of their thermoregulatory responses to approach by people is warranted.