tied to home | 95beachback vegetation on some of the remotest islands of the South Pa-
cific around the latitude of the Tropic of Capricorn (23.5°S), and they
are charmingly cooperative. Faced with a curious scientist, an incubat-
ing Murphy’s Petrel eschews the justifiable aggression of so many sea-
birds, and simply nibbles the hand that feels under its body to check its
legs for the presence of a metal ring, or to briefly remove the egg for
measurement.
Studies I completed in the early 1990s on the World Heritage Site of
Henderson Island, in the Pitcairn Islands, showed that the average length
of an incubation stint was 19 days. This means that complete incubation
of some 50 days was often completed in three stints, the male’s first
followed by the female’s, with the egg then hatching during the male’s
second stint. Wondering where the birds might have gone during their
long absences was an inevitable feature of campfire conversation. Could
they go as far as California, around 7,000 km to the north, where birds
were sometimes seen offshore in June, in the middle of incubation? But
it was not until 2011 that I had the opportunity to put geolocator de-
vices on 25 breeding birds to find out. Fortune smiled and we retrieved
18 of the devices two years later.
With the help of Tommy Clay, the output from the devices was down-
loaded and interpreted. We found a split in the main areas exploited by
birds off duty from the egg. Some travelled to low productivity seas
about 1,000 km south of Henderson whilst many others went north- east
towards the Humboldt Current off Peru and Chile. At the point the
birds turned for home, that is to say at the maximum distance from
Henderson, they were 3,500 km away on average. That equals roughly
the distance across the North Atlantic from Ireland to Newfoundland.
The furthest a bird ventured from Henderson on an off- duty excursion
was 4,500 km. Impressed by these numbers, we subsequently called on
the assistance of our colleague, Steffen Oppel, a dynamic and irrepress-
ible German who works for the Royal Society for the Protection of Birds
(RSPB). In 2015 he attached GPS devices to the incubating birds. The
total distance covered during the Murphy’s Petrels’ looping trips towards
the Humboldt Current was a remarkable 15,000 km.
Although the petrels’ huge journeys to prepare for incubation should
put the lid on human grumbles about Saturday morning shopping to fill