FIELDWORK REPORT 2004,
AND COLOUR-RINGING
DATA
INTRODUCTION
The British Trust for
Ornithology has agreed to provide a research grant of £200 per year for three
years to the Group, conditional on submission of a progress report, and
electronic submission of data to the BTO ringing scheme.
This Report summarises progress
for the second of those three years, 2004.
FIELDWORK
EFFORT
Group members travelled around
3,000 miles, and visited 216 current, or previously occupied, Raven nest sites.
128 nests were actually found,
and a further 16 territories were located.
As the primary fieldwork
objective was finding colour-ringed Ravens, and then the time-consuming task of
reading the two-letter code on the ring, there was insufficient time in some
parts of the survey area to find any pairs that had moved to an alternate site,
or locate the actual nest of some territorial pairs.
COLOUR-RINGED
RAVENS
A total of 45 colour-ringed
birds was found in 2004. As the
colour was identified, the age of all these birds is known, and the sex of most
of them has also been determined.
The unique two-letter code on
40 of these colour-rings was read, so these birds have been individually
identified, and their natal site is known. Of the 40, 28 had been found
previously, but the other 12 were found for the first time in 2004.
Since the Project started,
there are 180 different instances of colour-ringed Ravens being found at adult
nest sites. There are 129 instances
of the two letter code on the rings being read.
Many of these observations are of the same bird returning to breed for
several years, but 61 separate individual adults have been identified.
Several colour-ringed Ravens
have participated in the colonisation of the Peak District. Two of the rings
have been read, and the birds came from
TEN
YEAR OLD RAVENS
Two of the 27 birds ringed in 1994 (the first year of the
Project) were located in the breeding population in 2004. One of the rings was
read. The identity of the second 10-year-old bird is almost certainly known, as
there was a white-ringed bird at the alternate site in this territory for
several years. However, the current nest-site is extremely difficult to observe
because of the topography of the wood.
PRELIMINARY
RESULTS
Several preliminary results are apparent:-
All these preliminary conclusions will be analysed further
as more data becomes available.
ELECTRONIC
SUBMISSION OF DATA
The data for all the
colour-ringed Ravens that have been found and identified since the Project
started up until 2003 has been submitted electronically to the BTO ringing
scheme, via the IPMR return of
RAPID
POPULATION INCREASE
In the Group’s draft Report
covering the first phase of the Project (1994-99) evidence was presented for a
rapid increase in the breeding population. It
was estimated that it had increased from around 50 pairs in 1990 to 175 pairs in
1999. The breeding population has continued to increase rapidly, and was
estimated at around 250 pairs in 2003.
No concerted effort was made to
find new sites in 2004, but, even so, 2 were found (excluding several believed
to be alternates), suggesting that the population is continuing to grow. The
size of the non-breeding flocks of young birds also continues to increase, and
one of 80 birds was seen at the end of 2004.
DENSITY
Mid-Wales had the highest recorded Raven densities in
REPLACEMENT
OF INDIVIDUAL BIRDS WITHIN THE BREEDING PAIR
At some sites, several visits
are needed before a colour-ring can be read.
Between visits, the replacement of one of the two individual birds within
the nesting pair was definitely confirmed in one case, and probably occurred in
three other cases, in 2003. There were no observations of this occurring in
2004, but fieldwork effort was concentrated more on reading the colour-rings
earlier in the season, and any necessary repeat visits were made quickly, so all
except 7 were read before the end of March (half way through the breeding
season). Thus the likelihood of observing any replacement was much reduced.
INFIDELITY
/ SPERM COMPETITION
Ravens are reputed to mate for
life, but an instance was observed of a red – ringed female mating with a
green – ringed male from the adjacent nest, rather than the red-ringed male of
the pair. A note is available.
SECURITY
OF BTO RINGS
Several
instances were observed of colour-ringed birds no longer having the BTO metal
ring that was fitted at the same time as the colour-ring. No systematic
observation or record of this was made in 2004, but an effort will be made to do
so in 2005.
NOTE
Further information can be
provided on any part of this Report, on request.
The amount of fieldwork actually carried out was substantially more than the estimate on which the Grant Application was based.
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