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Tuesday, 23 November 2010

The last surviving captive (free-flying) BLACK-CROWNED NIGHT HERONS at Edinburgh Zoo

An update on Edinburgh Zoo-derived Black-crowned Night Herons.

Thanks to Jo Elliot, Animal Records Keeper at the zoo and formerly Senior Keeper of the Bird Section, we now have better information on what may be only two remaining birds. In summary:

Bird 1 - single vertically-split band half blue half yellow, seen April 09 to date (at least); this is a "new style" band, probably numbered, used on birds hatched 1989 to 1993 [a small possibility this bird is one ringed from 1997 to 2004, when sequences used were not recorded so carefully]; if caught numbers may be readable, and thereby pin down hatch year.

Bird 2 - red over blue left (blue appears green in photos), red right to 2006 but missing subsequently, bird seen to date; this individual seems to have old style bands used from 1983 to 1987 (possibly 1988?); again if caught it may be possible to confirm lack of numbers and also check for transponder fitted to (some?) birds in that period, thus confirm year.Alan's 2006 photos were key to this identification, since careful comparison with more recent images (thanks also to Bruce) suggests it is the same bird, it just dropped a colour band between 2006 and 2008 (and they are not closed bands, just a wrap round plastic ring like off a ring-binder, so they could easily be lost).

In addition, the zoo inform us that a bird with metal ring and red right, red-lime-blue left, ringed (and transpondered) in 1983 was definitely still at the zoo in 2000.

In summary, it is likely that the current ages of remaining two are 16 and 23 yrs respectively, and the metal-ringed bird was 17 yrs old in 2000, but without catching the former two are strictly unconfirmed. The current published longevity records I can trace are 16 yrs in Europe and 21 yrs for N American race (hoactli), the zoo birds are of course the latter.

Zoo not sure if they will try to catch birds, though it does not look to difficult a job to me given their regular occurrence (apparently routine at sealion feeding 11:15hrs) and if there are any volunteers (ringers?) for such I would happily pass on!

Finally, it is remarkable that these birds are probably out of the zoo in the local area for most of the time yet are hardly ever reported (Mike's sighting last New Year's Eve excepted, the only other adult in Lothian since 2001 was the bird at Bavelaw in Feb 2007, with a juv in Haddington in 2002 per BirdGuides only). Anecdotal info per zoo staff is that their birds "winter on the Water of Leith", also a report of one "seen regularly in Haddington", but these are unconfirmed and undated. Thus all further records of Night Herons in or out of the zoo, preferably with colour band details, would be most welcome!

Many thanks to all who have assisted - Stephen Welch