“For Earth Day, 2021, it is good to recognize, and address both the many environmental challenges and disasters, many human-caused, which are ongoing around the planet, but also to celebrate the many successful recovery and restoration projects, which aim to sustain, restore and protect the amazing natural heritage that Earth supports and that we, as humans, are blessed with and dependent on.
At this point, it is appropriate to provide an update on the progress of this year’s Cahow Breeding Season, as many of this year’s crop of chicks are already reaching the half-fledged point (6 to 7 weeks old). With the ongoing Covid-19 pandemic impacting human activities and societies world-wide for more than a year now (and Bermuda undergoing a second lock-down due to a surge in confirmed cases and deaths due to Covid as I write this report), I feel that it is very timely to deliver some good news, for a change!
1 day old Cahow chick photographed 2/28/2021
I can confirm that we now have a new record high number of 142 established breeding pairs of Cahows (up from 135 pairs in 2020); the number of breeding pairs on Nonsuch Island also increased to 27 pairs in 2021. There are 13 chicks currently on Nonsuch Island (including this year’s CahowCam 2 chick), tying the previous record of 13 fledged Nonsuch chicks in 2018. In addition, we have confirmed perhaps the highest recorded annual number of at least 14 newly establishing pairs, that will probably produce their first eggs next season. Nine of these new prospecting pairs are in the two new nesting colonies on Nonsuch island, which only produced their first fledged chick in 2009.
Nonsuch was originally a historic nesting location for the Cahow, from which they were completely wiped out by the 1620s through overhunting by the recently arrived human colonists and predation by introduced mammal predators. Near-fledged chicks were moved or translocated to artificial burrows during two projects on Nonsuch from 2004 – 2008 and 2013-2017 and hand-fed squid and anchovies, so they could imprint on Nonsuch instead of the original islets, which were vulnerable to hurricane flooding and erosion and sea-level rise. After fledging from Nonsuch, these birds spent 3 to 6 years at sea before they returned, and as hoped, they mostly came back to Nonsuch Island.
The first of these newly returned Cahows paired up on Nonsuch in 2009, producing the first naturally hatched chick recorded on Nonsuch Island for almost 390 years. Since this first chick, the new Cahow colonies on Nonsuch have increased from 1 pair in 2009 to 30 breeding pairs producing eggs in the 2021 nesting season. The number of successfully fledged chicks produced by these new Nonsuch colonies also increased from 1 to 89 chicks by 2020; if all 13 of this year’s crop of Nonsuch chicks fledge successfully in late May and June, then these colonies will have reached a significant milestone in having produced a total of 102 fledged chicks. It is worth noting that naturally fledging chicks only have about a 33 % return rate; in other words, of every ten chicks fledging, only 3 or 4 chicks survive the first 3 to 6 years at sea before they return to the nesting islands to choose nest burrows, pair up with a partner (generally for life), and start producing their own chicks.
Of these Nonsuch-born chicks, at least 16 have already returned as adults to pair up, 13 on Nonsuch and 3 on the other smaller nesting islands. Three of these birds have already produced their own chicks, producing the first “second-generation” Nonsuch Cahows.
For the 2021 Nesting Season, I can now confirm that there is a total of 71 chicks presently in nest burrows on all nesting islands, although there may be one additional chick in an especially deep nest that I am still trying to confirm. This is just below 2019s record number of 73 successfully fledged chicks, and is good news to convey on this year’s 2021 Earth Day!”
Jeremy Madeiros | Principle Scientist – Terrestrial Conservation | Dept. of Environment and Natural Resources | Bermuda