The 71st and final Cahow chick of 2018 fledged out to sea last June, here are the numbers that make this so significant:
The Bermuda petrel (Pterodroma cahow) is a gadfly petrel. Commonly known in Bermuda as the Cahow
The Cahow is the 2nd (or 3rd) rarest seabird on the planet;
The total number of Cahows now existing in the world is approx. 335 (including immature birds too young to breed);
Bermuda, specifically Nonsuch Island and the surrounding rocks, is the only location on the planet where the Cahows come to breed;
They were thought to be extinct for 330 years (1620 – 1951) making them a "Lazarus species";
There were only 17 – 18 breeding pairs in 1960 when the Cahow Recovery Program was started by David Wingate;
There were 55 breeding pairs in 2001 when David's successor Jeremey Madeiros took over the Program and started the translocation process to establish new breeding colonies on Nonsuch Island;
Under Jeremy's stewardship the breeding population doubled to a record number of 124 breeding pairs in 2018, including 15 pairs at the new Nonsuch colony; giving a total of 54 from Nonsuch.
71 chicks successfully fledged last season from all nesting islands, including 13 from Nonsuch;
Each breeding pair produces only 1 egg a year, of which 40% to 50% fail to hatch;
Eggs take 53 to 55 days to hatch, and are incubated by both adults;
Chicks take from 88 to 105 days from the time they hatch until they mature and fledge out to sea;
Adult Cahows abandon chicks up to 1 week before they fledge to sea, with the chicks flying to sea and learning to survive on their own;
Cahow chicks spend 3 to 6 years alone at sea before they mature andreturn to the breeding islands in Castle Harbour, Bermuda, to find a mate and nest burrow;
Banding studies have shown that only 28% to 38% of naturally fledging chicks survive their first years at sea and return to nest;
49 of the 102 cahow chicks translocated to Nonsuch Island between 2004 and 2008 by Jeremy Madeiros returned to Nonsuch or the other nesting rocks – this 48% return rate exceeds that of chicks raised solely by the adult birds.
Throughout the nesting season Jeremey conducts conservatively 2,000+ health checks, on average checking every chick in the colony every 2 days, often under very challenging weather conditions.
More amazing Cahow facts:
All male Cahows return to the breeding islands first at 3 to 4 years of age, and look for a empty nest burrow close to the nest they originally fledged from, often landing within a few feet of their original nest;
Females return later at 4 to 6 years of age to look for prospective mates;
Cahows nest in underground burrows or deep rock crevices; only nests deep enough to be completely dark are chosen;
80 % of all Cahows now nest in artificial concrete nest burrows constructed for them as part of the Recovery Program;
It takes approx 600 lbs of concrete to make a burrow;
Returned male Cahows try to attract prospecting female birds to their chosen nest burrows; if the female accepts the male as a mate, they will return to the same nest every year for the rest of their breeding lifespan (possibly 30 to 40 years);
Archival geolocational tags attached to the legs of adult Cahows by Jeremy Madeiros between 2009 and 2012 recorded the birds travelling amazing distances to gather food for the growing chicks;
The distance an adult travels to gather food to feed the chick once ranges from 1650 miles to 4500 miles or more, taking 4 to 9 days; the record distance for one feeding trip was almost 10,000 miles;
Cahows can cover distances of 250 – 500 miles a day, using free wind energy from Atlantic storms and gales;
Cahows eat mainly squid, small fish and shrimp-like crustaceans; studies with geolocators have also shown that Cahows predominantly feed in colder waters well north of the Gulf Stream;
Cahows are pelagic (oceanic) birds, which only visit land to breed; one of their adaptations for a life on the open ocean are special glands in their tube-like nostrils which enable them to drink seawater, by filtering out the salt so that they can use the resulting fresh water. The excess salt is sneezed out as drops of salty brine;
Another pelagic adaptation is an ability to sleep in flight by letting one side of the brain doze while the other half stays alert, then switching sides to let the other side get some rest.
The Cahow is Bermuda's National Bird.