Upper Thames Branch of
Butterfly Conservation
Annual Black Hairstreak Report 2006
by Stuart Hodges
A total of 995 Black Hairstreak
were seen in 2006. This is exceptional and we saw an average of 8.87 per hour, higher
than any previous year.
4 new colonies have been found and 1
was brought to my attention, a record that I had overlooked in 2004, Piddington
Bridge. Widnell Lane 15 seen, (nearest known colony three quarters of a
mile) a site searched several times in the past, a strong colony, a disused
railway line near Grendon Wood (nearest known colony one third of a mile
away) three seen, Gavray Drive near Bicester (nearest known colony over
four miles away) three seen, Weston wood (nearest known colony one third
of a mile away) one seen, and Piddington Bridge (nearest known colony
one and a half miles away) one seen. Three of the new sites had been searched
before, further confirming the probability that they are dispersing and
expanding their range.
Although we had a cold wet May, a
time when the Black Hairstreak is at the caterpillar stage, the cloudy nights
resulted in no late frosts. We also found high numbers in 2004 another year with
no late frost, so this is a further indication of the likelihood that late
frost could have a major impact on numbers.
The weather during the flight
period was again good with at least 7 days when the temperature was high enough
for them to be active for at least 12 hours, numbers peaked quickly after about
a week and this lasted for only three or four days before falling away.
Searching was again successful for
both eggs (3 found) and pupae (6 found). We now have timed counts for 9 eggs
taking an average of 190 minutes each to find, 6 pupae taking 76 minutes each
to find (pupa searches in 2005 were not timed). In two years we have found 12
pupae and our observation found that only 5 emerged, the other 7 disappeared,
probably taken by birds.
One egg hatched 5th or
6th of April another found already hatched on the 15th
and the last not until early June, leaving one speculating as to what would
become of it.
A Black Hairstreak having just laid an egg -
photograph © Dave Wilton
We have established that a strong
colony now exists at the M40 Compensation area. On the 10th of June
the first adult of the year was found there and then on the 14th
June 19 were seen in poor weather conditions. This area as mentioned last year
was established primarily for the Brown and Black Hairstreak, the first Black
being seen in 1999. Transects in 2005 indicated a colony existed.
The smaller colonies in less
favourable habitat did not have the same percentage increase in numbers seen
elsewhere.
In the last twelve months
management of Blackthorn has taken place at 4 sites, and plans are being made
for management at 3 other sites. We have continued to keep landowners informed
about the Black Hairstreak, but I need to make more effort to find more of the
landowners.
Once again we have a very good set
of records, I am very grateful for all
the effort everyone has put into
monitoring. This coming year will be our tenth recording year.
If you would like more
information, or wish to help with the surveying, or perhaps require management
advice, please contact the branch Black Hairstreak champion:
Stuart
Hodges Tel:
01296 730217 or email me
Yearly comparisons from our Monitoring:
|
|
1998 |
1999 |
2000 |
2001 |
2002 |
2003 |
2004 |
2005 |
2006 |
Total |
|
Total
number of Colonies |
|
|
|
|
|
|
|
|
|
|
|
ever seen
in Bucks & Oxon |
|
|
|
|
|
|
|
|
|
93 |
|
Sites
visited by the recording group |
|
31 |
22 |
36 |
28 |
29 |
40 |
38 |
51 |
78 |
|
Colonies
seen by the recording group |
7 |
13 |
9 |
15 |
9 |
13 |
34 |
34 |
39 |
44 |
|
Colonies
seen since 1990 |
|
|
|
|
|
|
|
|
|
50 |
|
New
colonies found since 1998 |
2 |
|
1 |
|
|
2 |
2 |
1 |
6 |
14 |
|
Colonies re-discovered
seen pre 1990 |
1 |
5 |
2 |
4 |
1 |
1 |
2 |
1 |
|
17 |
|
Individual
Butterflies seen |
19 |
28 |
73 |
90 |
123 |
109 |
525 |
258 |
995 |
|
|
Hours Spent
Looking for the B.H. |
|
|
|
90.5 |
52.8 |
48.7 |
76 |
99 |
112 |
|
|
People helping
with the recording |
4 |
9 |
12 |
13 |
15 |
16 |
17 |
24 |
21 |
|
|
Days when
the Weather was suitable for the B.H. to be active |
|
|
16 |
18 |
18 |
21 |
22 |
28 |
28 |
|
|
Hours when
the Weather was suitable for it to be active |
40 |
90 |
105 |
149 |
151 |
167 |
150 |
176 |
234 |
|
Figure 1
Colony Information:
|
The current
number of colonies in Bucks and Oxon* |
48 |
|
Colonies
within Woodland |
5 |
|
Colonies in
Woodland edge sites |
21 |
|
Colonies at
Hedgerow Thicket and Copse Sites ** |
22 |
|
Some of the Features of these Colonies: |
|
|
Hedgerow
Colonies at Roadside sites |
8 |
|
Colonies
Associated with Bridleways and Footpaths |
9 |
|
Colonies
alongside Railways |
4 |
|
Colonies
with Private Landowners |
19 |
Figure 2
*Estimate only. Colony numbers have increased since 2004, in some cases it is
more difficult to define the boundaries between them.
**Two of these colonies extend out along
hedgerows from woodland for over 100
metres.
Numbers seen per Hour:
Figure 3
Year on Year Difference of Numbers Seen per Hour:
Figure 4