As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Sunday, 13 March 2016

Winged Predators and an Ill wind threaten newly fledged Tahiti Monarchs

By Caroline Blanvillan, Mon, 29/02/2016 - 07:29

Half way through, 2015/2016 breeding season has been a record year for the critically endangered Tahiti Monarch.  The good news is that the 53 adults so far this year have, initially, fledged 14 young – with at least one more expected. 

But this year was different in not a good way.  Maybe because of El NiƱo, there was an ill wind blowing through the valleys.  There was the sudden disappearance of five young after fledging.  BirdLife partner SOP Manu and their illustrious community helpers we left with only nine survivors among the 14 that flew in 2015.

So what has happened? Because no one was able to watch these birds continuously, SOP Manu staff can only speculate on the culprit/s.  They need the services of a real detective.  Something that would challenge Hercule Poirot! 

In 2015 the obvious nest predators - black rat, Myna and blackbirds can be eliminated from the list of suspects. Why? Because there are no more, thanks to rat control by SOP Manu and the trapping of blackbirds over four years by the volunteer network. There are no longer any blackbirds in monarch territories and that is a major reason for the baby boom amongst monarchs over those last few years. Black rats are controlled but still some of small nests are still the scene of a bloody home invasion.  Other flying species like robins are also killed as are even many bulbuls - and they fly and are not normally effected by rats!

Number one suspect is the swamp harrier.  Originally from New Zealand and falsely called hawk in French Polynesia, it was introduced to Tahiti in 1885 by the German consul, with the intention of limiting the number of rats.  From Tahiti, they flew onto other islands severely impacting on the endemic species of those islands without making any difference at all to the populations of rodents that are able to increase the size of their litters to compensate for losses due to predators.   They launch themselves, slalom between trees at full speed, and fall on their prey. The endemic land birds, which have evolved over millions of years in environments free from such aggressive predators, are easy prey.  

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