The year 2021 began with yet another lockdown and, as is so
often the case, the sequel was miserable. The first lockdown in 2020 was novel,
interesting and characterised by a warm, dry and sunny spring. January in 2021
was cold, dark and oppressive and we approached the national lockdown with a
sense of weariness and resignation. Fortunately, I was able to find some cause
for cheer – I could find the time to survey birds in my garden and complete a
full year of study. Having gained my C permit in April 2020 I was unable to
start ringing in my garden until part way through that year. This time, I could
aim to complete a full year of study to provide a baseline for monitoring my
garden birds over time.
Part of that study would involve ongoing participation in
the new Garden CES (Constant Effort Site) project which was introduced by the
BTO to provide an outlet for qualified ringers with time on their hands and limited
access to traditional sites in 2020. I had elected to contribute to the Garden
CES in its first year and planned to continue my involvement in 2021. Whilst I
was very glad indeed that the lockdown had been lifted by May when the CES
began, this did restrict my ringing activities as I could only keep the nets up
in the garden until the necessitated commute to work. In 2020, I was able to
keep the nets open until 11am which was not an option in 2021. This was a real
shame because I learnt towards the end of the year that the data collated in
2021 couldn’t be used in a comparative study by the BTO as the timeframes for
ringing between the years were not the same – I guess the clue was in the name
– ‘Constant’ Effort Sites. For that reason, the CES data collected in 2021 also
represents a baseline for comparison with future years – at least for the
purpose of BTO analysis. However, it’s worth noting that the number of birds
caught in the latter stages of the 2020 ringing sessions tended to fall away
quite quickly, so the data is broadly comparable for the purposes of this
report.
The total number of birds caught in the 2021 CES period (167
= 13.92 per session) was almost the same as 2020 (168 = 14 per session) and the
species count was similar with 20 species caught in 2020 and 23 species in
2021. However, the assemblage of species was slightly different in this second
CES, with 7 new entrants in 2021 (Blackcap, Garden Warbler, Goldcrest, Magpie,
Marsh Tit, Song Thrush and Stock Dove). Four species captured in 2020 did not
feature in the 2021 CES data set (Chiffchaff, Great Spotted Woodpecker, Jay and
Whitethroat) although all, bar Whitethroat, were caught at other times in the
calendar year of 2021.
There is no way of drawing statistically significant
comparisons between years when looking at the abundance of each species, but
there are some interesting figures to consider. In particular, the number of
Goldfinches (22; 13 in 2020) and Greenfinches (7; 3 in 2020) captured in 2021
was considerably higher and the number of Long-tailed tits (3; 11 in 2020) and
wrens (3; 7 in 2020) was lower. I will return to blue tit numbers later.
Table 1: Garden CES 2021 – Ringing Records (figures in green higher than 2020; figures in red are lower than 2020)
|
Species
/ Visit |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
Total |
Average |
|
Blackbird |
|
1 |
|
|
1 |
3 |
1 |
1 |
|
|
|
|
7 |
0.58 |
|
Blackcap |
|
|
|
|
|
|
|
1 |
2 |
1 |
1 |
|
5 |
0.42 |
|
Blue Tit |
|
|
1 |
2 |
7 |
4 |
6 |
3 |
2 |
4 |
9 |
8 |
46 |
3.83 |
|
Bullfinch |
|
|
1 |
|
|
|
|
1 |
|
|
|
|
2 |
0.17 |
|
Chaffinch |
1 |
2 |
|
|
|
|
|
|
|
|
|
|
3 |
0.25 |
|
Chiffchaff |
|
|
|
|
|
|
|
|
|
|
|
|
0 |
0.00 |
|
Coal Tit |
|
|
|
|
|
|
|
|
|
|
1 |
|
1 |
0.08 |
|
Dunnock |
1 |
|
|
|
1 |
1 |
3 |
4 |
2 |
2 |
|
|
14 |
1.17 |
|
Garden Warbler |
|
|
|
|
|
|
|
|
|
1 |
1 |
|
2 |
0.17 |
|
Goldcrest |
|
|
|
|
|
|
|
|
|
1 |
|
|
1 |
0.08 |
|
Goldfinch |
1 |
1 |
1 |
1 |
8 |
1 |
4 |
3 |
|
|
2 |
|
22 |
1.83 |
|
GS
Woodpecker |
|
|
|
|
|
|
|
|
|
|
|
|
0 |
0.00 |
|
Great Tit |
2 |
1 |
1 |
|
|
1 |
|
2 |
|
|
4 |
2 |
13 |
1.08 |
|
Greenfinch |
|
1 |
|
|
2 |
|
1 |
2 |
|
1 |
|
|
7 |
0.58 |
|
Jackdaw |
|
1 |
|
1 |
|
|
|
|
1 |
|
|
|
3 |
0.25 |
|
Jay |
|
|
|
|
|
|
|
|
|
|
|
|
0 |
0.00 |
|
Long-tailed Tit |
1 |
|
|
1 |
|
|
|
|
|
|
1 |
|
3 |
0.25 |
|
Magpie |
|
1 |
|
|
1 |
|
|
|
|
|
|
|
2 |
0.17 |
|
Marsh Tit |
|
|
|
|
|
|
|
|
|
|
1 |
|
1 |
0.08 |
|
Nuthatch |
|
|
|
1 |
|
|
|
|
|
|
|
|
1 |
0.08 |
|
Robin |
2 |
|
3 |
|
1 |
|
2 |
1 |
1 |
1 |
2 |
|
13 |
1.08 |
|
Song Thrush |
3 |
|
|
|
|
|
|
|
|
|
1 |
|
4 |
0.33 |
|
Starling |
1 |
3 |
2 |
1 |
1 |
|
|
|
|
|
1 |
1 |
10 |
0.83 |
|
Stock Dove |
|
1 |
|
|
|
|
|
|
|
|
|
|
1 |
0.08 |
|
Whitethroat |
|
|
|
|
|
|
|
|
|
|
|
|
0 |
0.00 |
|
Woodpigeon |
|
|
|
1 |
|
|
|
1 |
|
|
1 |
|
3 |
0.25 |
|
Wren |
|
1 |
|
|
|
|
|
1 |
|
1 |
|
|
3 |
0.25 |
|
Total |
12 |
13 |
9 |
8 |
22 |
10 |
17 |
20 |
8 |
12 |
25 |
11 |
167 |
13.92 |
|
Species
number |
8 |
10 |
6 |
7 |
8 |
5 |
6 |
11 |
5 |
8 |
12 |
3 |
23 |
7.42 |
In addition to the CES sessions, there were many more
occasions during the year when I was able to ring in the garden – in total
there were 54 separate sessions in comparison with 48 in 2020. However, these
were spread across the full year, whereas ringing in 2020 was limited to the
months of May to December. This makes comparisons tricky once more, but there
are some interesting figures in table 2 which may provide some evidence of
changes in abundance between years.
Table 2: Ringing
Totals for 2020 and 2021
|
|
2020 |
2021 |
||||
|
Species |
Ringed |
Retrapped |
Total |
Ringed |
Retrapped |
Total |
|
Blackbird |
16 |
6 |
22 |
18 |
12 |
30 |
|
Blackcap |
6 |
0 |
6 |
24 |
1 |
25 |
|
Blue Tit |
118 |
30 |
148 |
97 |
48 |
145 |
|
Bullfinch |
3 |
3 |
6 |
3 |
0 |
3 |
|
Chaffinch |
10 |
0 |
10 |
1 |
3 |
4 |
|
Chiffchaff |
1 |
0 |
1 |
3 |
0 |
3 |
|
Coal Tit |
11 |
4 |
15 |
7 |
7 |
14 |
|
Dunnock |
21 |
26 |
47 |
18 |
36 |
54 |
|
Firecrest |
1 |
0 |
1 |
2 |
0 |
2 |
|
Garden Warbler |
0 |
0 |
0 |
2 |
0 |
2 |
|
Goldcrest |
8 |
2 |
10 |
16 |
5 |
21 |
|
Goldfinch |
35 |
1 |
36 |
55 |
8 |
63 |
|
Great Spotted Woodpecker |
4 |
0 |
4 |
1 |
0 |
1 |
|
Great Tit |
47 |
10 |
57 |
35 |
10 |
45 |
|
Green Woodpecker |
1 |
0 |
1 |
0 |
0 |
0 |
|
Greenfinch |
9 |
0 |
9 |
17 |
2 |
19 |
|
Jackdaw |
6 |
0 |
6 |
4 |
1 |
5 |
|
Jay |
1 |
0 |
1 |
1 |
0 |
1 |
|
Lesser Redpoll |
1 |
0 |
1 |
1 |
0 |
1 |
|
Long-tailed Tit |
25 |
20 |
45 |
21 |
3 |
24 |
|
Magpie |
0 |
0 |
0 |
4 |
0 |
4 |
|
Marsh Tit |
0 |
0 |
0 |
1 |
0 |
1 |
|
Nuthatch |
2 |
1 |
3 |
5 |
4 |
9 |
|
Redwing |
6 |
0 |
6 |
13 |
0 |
13 |
|
Robin |
21 |
20 |
41 |
22 |
31 |
53 |
|
Siskin |
2 |
0 |
2 |
8 |
0 |
8 |
|
Song Thrush |
0 |
0 |
0 |
8 |
0 |
8 |
|
Starling |
32 |
1 |
33 |
24 |
3 |
27 |
|
Stock Dove |
0 |
0 |
0 |
1 |
0 |
1 |
|
Whitethroat |
2 |
0 |
2 |
0 |
0 |
0 |
|
Woodpigeon |
2 |
1 |
3 |
4 |
1 |
5 |
|
Wren |
10 |
5 |
15 |
11 |
6 |
17 |
|
Total |
401 |
130 |
531 |
427 |
181 |
608 |
|
Per session |
8.4 |
2.7 |
11.1 |
7.9 |
3.4 |
11.3 |
Whilst recognising the limitations of any comparisons
between years, it is interesting to note that many more Greenfinches, Goldfinches,
Blackcaps, Goldcrests and Song Thrushes were caught in 2021, whilst the number
of Chaffinches and Tits was lower. The Blue Tit data is particularly
interesting given earlier speculation about the impact of the cold spring on
productivity. It has been suggested that the cold weather delayed the emergence
of oak leaves and their favoured caterpillar prey, resulting in greater rates
of nest failure and low recruitment to the population of blue tits nationally.
However, my localised data shows that whilst the population of Blue Tits may
have decreased slightly (2.7 per session compared to 3.1 per session in 2020),
the number of juvenile birds in 2021 was considerably higher – see table 3.
Given that the span of the year in which juvenile birds were present was
sampled equally in both years, this comparison seems valid. The number of Blue
Tits caught in the 2021 CES period was actually higher overall (46; 36 in
2020), but this is largely down to the number of juveniles. It was striking
that no Blue Tit adults were caught in the first 2 CES sessions at all.
Table 3: Blue Tit
adult : juvenile ratios in 2020 and 2021
|
|
2020 |
2021 |
|
Adult totals |
88 |
40 |
|
Juvenile totals |
60 |
105 |
|
Adult : Juvenile |
1 : 0.7 |
1 : 2.6 |
If anything, this data supports the notion that Blue Tit
productivity was actually higher locally in 2021, with many more juvenile birds
present than 2020. Conversely, adult survival may have been lower in 2021 –
perhaps the challenge of feeding nestlings with limited food supplies had more
of an impact on exhausted adults? It will be interesting to see the BTO data on
Blue Tits to see if my figures align with any national trends.
In time, I sincerely hope that my data will provide a useful
contribution when aggregated within the national data sets analysed by BTO. At
the moment, it is early days for ringing in Chesham Bois, so I can’t really
analyse trends yet, but that time will come. Hopefully it will reveal
recoveries in bird numbers and variety through time from this baseline, which
is surely lower than it would have been in preceding decades. Nevertheless, my
garden ringing activity has provided me with some interesting insights into my
small local patch already. I would never have predicted such a variety of
species – indeed, before ringing, I had never seen Firecrests, Garden Warblers
or Whitethroats in my garden – a true revelation. I wouldn’t have been able to
speculate about Blue Tit survival and productivity and I wouldn’t have had any
appreciation of the total number of birds visiting my patch. There are some
regular repeat visitors - one poor robin has been caught 26 times (!) – but
there are many more individuals that pass through, as I have caught 43 robins
in total across two years.
The ringing projects for 2022 are now underway and I can’t
wait to find out what they will throw up – any forecasts for new ringing
records or winners and losers in 2022 – answers on a postcard to Chesham Bois
please.
By Ian CookseyStock Dove - First ringing record for the garden A male Starling in full breeding plumage A juvenile Marsh Tit - a first ringing record for the garden Juvenile Garden Warbler - another first ringing record for the garden A male Chaffinch - a very rare sight in 2021
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