Tweets,

Michael Price's recent post contains an apparent error if posted
under this particular topic. It's understandable, however, because he
has taken the BOU categories from a summary on its website.

The fuller text (in Ibis 141: 175-180, 1999) refers readers to a
fuller explanation of the categories in British Birds 91: 2-11, 1998.
There is written the following:

"Category D was introduced in 1971 to act as a holding category for
species that may qualify for the main list in the future...This category
formerly included a number of subdivisions...Category D2 was for species
that arrived with 'a combination of ship and human assistance.' Ship
assistance is no longer a barrier to admission to the national list as
it is now regarded as a normal means of dispersal. Human assistance is
a different matter..."

Therefore, Michael's post under the topic of "Ship-assisted
Vagrants", taken with his presumption that the Xantus's Hummer would be
placed in Cat. D by the BOU, might mislead people to believe that ship
assistance by itself would place a bird into Category D in Britain.
That simply is not so. Coupled with evidence of 'human assistance'
enroute, however, it might.

The BOU rarely adds birds to Category D any more, preferring to keep
a report 'in circulation' until the situation is reasonably clear one
way or the other. If a report cannot be placed into one of the
other categories, it tends not to be listed at all.
---------------------------------------------------------------
P W (Bill) Smith
Grays Harbor, Washington USA
pwsmith at techline.com