Cahow continues comeback from near extinction
Bermuda’s national bird has bounced back from the brink of extinction with a record-breaking breeding season.
Jeremy Madeiros, the chief terrestrial conservation officer for the Department of Environment and Natural Resources, said in the Bermuda Audubon Society’s autumn newsletter that the number of breeding pairs rose to 131 this year and 73 chicks were born.
He added: “Only 17 or 18 breeding pairs remained in the early 1960s, when conservation and recovery management of the breeding population and potential threats began under David Wingate.
“By 2000, when Dr Wingate retired and I took over the recovery project, the number of breeding pairs had increased from 53 to 55.
“Nineteen years on, I am happy to report that the number of established breeding pairs of cahows has increased to 131.”
Mr Madeiros said chicks this year were lighter than average, which suggested it was more difficult for adults to find food.
But he added that a record number of 73 chicks fledged, including 12 on Nonsuch Island.
Mr Madeiros said: “Low weights resulted in a total of eight chicks having to be taken into care and given supplemental feeding of fresh anchovies. I am happy to report that seven of the eight chicks recovered enough weight to fledge successfully out to sea.
The numbers broke last year’s record of 124 breeding pairs and 71 fledged chicks.
The cahow, an endemic seabird also known as the Bermuda petrel, was believed to have been wiped out by early colonists by the 1620s.
But the species was rediscovered in 1951 when they were found in nests on rocky islets in Castle Harbour, which sparked a major conservation effort.
Mr Madeiros said cahows had also expanded the number of sites where they nest.
He explained that the birds only nested on four small islets in Castle Harbour in 1951, but they were now established in two colonies on Nonsuch Island after a relocation effort.
The species also colonised Southampton Island on their own in 2013.
Mr Madeiros said: “The total breeding habitat has increased from four islets totalling 3.4 acres, to six islands totalling 22.3 acres.
“The new Nonsuch Island colonies are especially important for the future recovery of the cahow as they could potentially support several thousand nesting pairs.
“The original nucleus of pairs consisting solely of translocated cahows at the Nonsuch sites are now increasingly being supplemented by non-translocated prospecting birds attracted from the original nesting islets, and of chicks produced by the new Nonsuch breeding pairs, of which at least seven have now returned to Nonsuch Island to choose nest burrows and mates.”
Mr Madeiros added that researchers had also launched a GPS tagging scheme this year to learn more about the birds’ movements when at sea.
And blood and feather samples were collected from 90 adult cahows to test what pollutants the birds are exposed to and if that might contribute to high levels of infertility and failed eggs.
But the Audubon Society newsletter had bad news about Bermuda’s common tern population, which has been devastated by hurricanes during their nesting seasons.
Only four chicks from three nesting pairs of the species were recorded in Bermuda over the summer.
Humberto presented another threat to the terns, which were still on the island when the Category 3 hurricane brushed Bermuda.
Erich Hetzel said: “After the hurricane’s passing, a maximum of four local terns have been seen. What has become of the rest remains to be seen next year.
“Unfortunately, the parade of hurricanes that now menace and hit Bermuda with astonishingly high frequency is threatening to drive our common tern population to extinction.”
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