Harvey
I had sort of assumed that with altricials, cessation of feeding of the
young by adults was a sort of dividing line between dy and not dy.
I agree that with precocials this is not a generally useful definition.
With the precocials I sort of figure that if the young stick fairly
close to the adults then there is some sort of dy relationship (Perhaps
teaching the young about what hawks can do if you don't keep and eye on
them?)
With altricials it seems to me, when parents stop feeding the young is
not only a marker of a stage in the breeding process but also a marker
of time and place. Dy does show whether the particular spot is useful in
the breeding process - even if the nest was beyond some notional
boundary. Post-dy is, arguably, a possible marker that not only has the
breeding process completed but that breeding may have occurred somewhere
else. Using hundreds if not thousands of breeding records, patterns of
id, ih, co, ne, ny, dy in the data are a useful marker of overall
breeding timing.
regards
Con
On 27/01/2015 5:11 PM, Perkins, Harvey wrote:
Con this is a vexed and ongoing issue.
To be blunt (and I may incur the wrath of some other COG members or database people), I
treat DY as meaning "dependent young", whatever that description might entail,
and do not restrict it to whether I actually saw food being passed from parent to
offspring. How would you treat a clearly dependent offspring of a precocious bird (i.e.
on that feeds itself from hatching, such as Black-fronted Dotterel)?
As far as I'm concerned, the indicator of DY is to indicate that the bird is dependent on
a parent as a subset of categories of codes whose overall purpose is to capture in the
COG records that breeding has occurred. Without such an interpretation, as you said, the
database loses a lot of valuable information. If DY was meant to indicate "seen
being fed by parent" the code should have been something else. That said, I do agree
that the code DY should only be used when a bird is clearly dependent on a parent, a
decision which can still be fairly subjective when the bird is IPDY or even IWDY.
My thoughts...
Harvey
Dr Harvey Perkins
CRC Programme Liaison Officer
Phone +61 2 6213 7472
Email:
-----Original Message-----
From: Con Boekel
Sent: Tuesday, 27 January 2015 4:49 PM
To: cog list
Subject: [canberrabirds] 'Dy or not dy?' that is the question.
Going for a constitutional this afternoon in BMNR, I noticed that there was a
young Noisy Friarbird begging noisily. The parent bird was busy feeding itself
and on four or five occasions found some prey and ingested it. Each time the
begging youngster approached the adult bird too closely and increased its
begging investment (more and louder calls) the adult bird would engage in some
sort of behaviour which clearly contained the message: 'Rack off'. So, not dy.
There was a similar scenario with two adult and one young Yellow-tailed Black
Cockatoo at JWNR two days ago. Again the adult bird, with a tasty morsel -
freshly hewn from its former home inside an acacia branch - lunged at the young
bird as if to say, 'Rack off!'. Not dy.
Then again, this afternoon, two Sacred Kingfisher youngsters in BMNR sat around
begging, apparently waiting to be fed. The parent was about, did not catch
anything with which to feed them and did not feed them. Not dy.
A group of three young Noisy Friarbirds along Upper David Street, the cultural
boundary between Turner and O'Connor, were all begging lustily.
But they were all also actively feeding on whatever is infesting the street
eucs, said infestation having attracted significant numbers of the usuals. Not
dy.
Also attracted to said infestation were two Red Wattlebirds. One of which was
feeding and the other of which was begging. No transfer of food occurred. Not
dy.
In a garden nearby, a young Magpie-lark was begging in the harsh and strangled
tones with which young Magpie-larks may signal that their voices are breaking.
Its companion was actively feeding itself but not the young bird. Not dy.
Four gardens along, a young Pied Currawong was begging (disconsolately, if one
wanted to be anthropomorphic about it) and not being fed. Not dy.
If COG had a breeding category 'IPDY' (Immediate Post Dependent Young) or
possibly even 'IWDY' (I Want to be a Dependent Young) I would have had many a
record to add to the COG database, including a rare breeding record for the
YTBC.
But alas, I came up with many an NDY instead.
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