Watercress Wildlife Association
Butterfly Survey Report 2015
Introduction
A small dedicated group of volunteers each year undertakes regular surveys along a set transect around the reserve recording all the butterflies seen.
Surveys are conducted between the beginning of April and the end of September. This regular and systematic survey gives us information about the state
of butterflies on the reserve, the species, their numbers and changes. Numbers can fluctuate wildly from year to year as some species have boom and bust
cycles and butterflies are very sensitive to weather conditions. However, over time we can build a picture as to what species use the reserve and whether
any change is occurring. We can use this information to assess whether we are managing the reserve well and meeting our objectives. The butterfly
survey data is also shared with Herts and Middlesex Butterfly Conservation and becomes part of the regional and national dataset where it can be used to
monitor changes of climate, habitat etc. One off observations are also useful, in particular they can alert us to the unusual which might be missed on a
regular survey.
Change in number of species over time
Number of species on site
20
No. soecies
15
10
5
0
2009
2010
2011
2012
2013
2014
2015
We have records now for 7 years. The graph shows an encouraging overall increase over time. We hope this reflects the attempts to make the site more
diverse and butterfly friendly (more nectar rich flowers on the butterfly garden, more grass and tree species as food sources for caterpillars). The plan is
that if the site is suitable for butterflies this will also increase the number of other invertebrates on site which is not only more interesting for us but also in
turn provides a better food supply for other species such as birds. However, we will need to continue to interpret the data carefully. On such a small site
we will never be able to attract a very large range of species, the increases could be due to chance or may just reflect the increasing skills of our surveyors!
The Weather in 2015
Because adult butterflies are very sensitive to weather – usually only flying in warm, dry and calm conditions, most butterfly reports include a summary of
the year’s weather in order to help interpretation. 2015 had fluctuating periods of weather. The early spring was very mild so many butterflies were seen
early on the wing. May was cool and wet. June was warm and sunny but later in the summer again there were several cool and wet periods.
The species 2015
The following graphs show the species and their flight times. For comparison, the 2014 graphs are shown in Appendix 1.
Numbers
The Whites
20
10
0
1 2 3 4 5
6 7 9 10
11 12 13 14
15 16 17
18 19 20
21 22 23
Week
24
Brimstone
Green-veined White
Large White
Orange-tip
25
26
Small White
The Brimstone did slightly better than in 2014 probably
benefitting from the mild spring and had a long drawn out
flight period. There was a late August peak as it recovered
from a cool summer. The Orange tip is a spring butterfly
but did not seem to be too impeded by the wet May. The
Small White has its main peak in July and August but is on
the wing for much of the summer and seemed to do better
than the Large White. The Large White also has its main
peak in July and August but unlike elsewhere we did not
see the bounce back in numbers from a relatively poor
year in 2014. The Green Veined White has two main
broods, one in early spring and the second in late July and
August. Regionally the second brood was the largest but
on the reserve the early brood did slightly better.
The Browns
Numbers
10
5
0
1 2 3 4
5 6 7
8 9 10
11 12 13
14 15 16
17 18 19
20
21
22
23
24
25
Generally it was not a good year for numbers of Speckled
Wood but they showed a typical peak in late
August/September. The Gatekeeper usually has a
relatively short mid-summer season but we recorded
some late specimens whose emergence may have been
delayed by poor weather. The Ringlet has only recently
been recorded on the reserve. It likes damp shady
grassland and may reflect the growth of trees on the
reserve. It will be interesting to see if it returns in 2016
now that shade has been reduced over the winter by
cutting back of some trees. Meadow Browns were low in
number.
Week
Speckled Wood
Gatekeeper
Meadow Brown
Ringlet
Vanessids and Admirals
Numbers
8
6
4
2
0
1 2 3 4
5 6 7 8
9 10 11
12 13 14
15 16 17
18 19 20
21 22
23
24
25
26
Weeks
Comma
Painted Lady
Peacock
Red Admiral
Small Tortoiseshell
White Admiral
Commas emerged well in April probably benefitting
from the warm spring. The later peaks were a little late.
The Painted Lady is not always recorded on the site - it is
a migrant from North Africa and does not always make
it in any numbers to the UK. This year it did reasonably
well in June and July (a little later than usual) and the
second peak may have been a second British bred
generation. The Peacock, like elsewhere in Hertfordshire
did reasonably well starting a little earlier and average
and with more successive peaks than usual. Red Admiral
numbers were well down on the previous year.
Regionally the Small Tortoiseshell had an early peak in
spring. We did not pick this up but picked the second
brood in late June and July which continued into August
although elsewhere sightings were rare in August due to
the poor weather. It was pleasing to see and record for
the first time the White Admiral as this is a species in
serious decline.
Others
Numbers
6
4
2
0
1
2
3
4
5
6
9
10
12
14
15
17
18
19
Weeks
Large Skipper
Common Blue
20
21
22
23
24
25
26
Skippers again showed a decline. No small
skippers were seen and The Large Skipper
was in small numbers. This may be due to the
increased shade as the trees have grown and
spread on the reserve. The Holly Blue
generally had a good year and this was
reflected in our records. This is a species
subject to boom and bust cycles. It was also
good to record Common Blue (missing from
2014). Generally it had a good year this year.
The first peak was late due to the poor May
weather and similarly the second August
brood.
Holly Blue
White Admiral
Ringlet
Holly Blue
Common Blue
Meadow Brown
Large Skipper
Brimstone (male)
Painted Lady
Appendix 1 2014 results
The Whites
40
20
0
4/6/2014
5/6/2014
6/6/2014
7/6/2014
8/6/2014
9/6/2014
Brimstone
GV White
S. White
Orange Tip
L. White
Browns
15
10
5
0
4/6/2014
5/6/2014
6/6/2014
7/6/2014
8/6/2014
9/6/2014
Speckled Wood
Gatekeeper
Meadow Brown
Ringlet
Admirals & Vanessids
6
4
2
0
4/6/2014
5/6/2014
6/6/2014
7/6/2014
8/6/2014
9/6/2014
S. Tortoiseshell
Comma
Red Admiral
Peacock
Others
3
2
1
0
4/6/2014
5/6/2014
6/6/2014
7/6/2014
8/6/2014
9/6/2014
L. Skipper
Holly Blue
M Harris June 2016