Download Lisvane wildfowl report 2013-14

Waterbirds at Lisvane/Llysfaen Reservoir,
North Cardiff
October 2013 – March 2014
Report to Natural Resources Wales
David Gilmore
Mike Powell
Phil Bristow
Rob Thomas
Summary
Waterfowl counts were carried out at Lisvane (Llysfaen) Reservoir, North Cardiff, by a team
of four observers, on 76 dates over the 6-month period 1st October 2013 – 31st March 2014
(i.e. covering 42% of the 182-day study period). A total of 25 waterbird species were
recorded over the 6-month period, and the mean number of species seen on each date was
10 (range 5-14 species). Species richness (number of species) declined over the winter,
though there was considerable variation between species in the timing of peak abundance.
The five most abundant species (in decreasing order of peak abundance) were: Black-headed
Gull (peak abundance 161), Canada Goose (138), Lesser Black-Backed Gull (134), Tufted Duck
(99) and Pochard (39). A full systematic list of species is presented in the main text, with
maximum, minimum and average (mean and median) winter abundance of each, together
with graphs of the seasonal changes in species abundance.
Introduction & Methods
Rationale
The aim of the study was to provide an objective assessment of the use of Lisvane Reservoir
by waterbirds, across the 2013-14 winter period (October – March). Counts were organised
to provide approximately uniform coverage in each of the six months, and to include counts
distributed across the daytime period, including dawn and dusk counts.
Field Methods
Waterbird counts at Lisvane Reservoir were carried out over a 6-month period (October
2013 - March 2014), by four experienced local observers; David Gilmore (Glamorgan County
Bird recorder), Phil Bristol, Mike Powell and Rob Thomas. The observers used binoculars and
telescopes to count each species of waterbird present, primarily from the car park area in
the SW corner of the reservoir, from where almost the whole of the reservoir is visible
simultaneously. Visits typically lasted 30-60 mins., and as well as the numbers of each
waterbird species, the observers noted details of the distribution of the birds, the prevailing
weather conditions, and any human disturbance.
Data Analysis & Graphics
Simple descriptive statistics are presented for each species; the mean and median counts
across all visits throughout the study period, maximum and minimum counts for the study
period, and the month(s) in which the main peak(s) of abundance occurred.
Statistical models of abundance were implemented in R statistical software (version 3.2.2, R
Development Core Team 2014). Generalised Additive Models (with Poisson or negative
binomial error structures as appropriate) were used to model abundance in relation to date.
Non-linear parameters (“k-values”) of k = 6-8 were used, selected on the basis of model
diagnostics and information criterion values. In the graphs of abundance of each species
across the study period, the blue data points show the actual count for each date. The solid
red line shows the modelled relationship between abundance and date, with the dashed red
lines showing the standard error around this modelled relationship.
To provide a national and international context for the Lisvane survey data, we also present
national (UK) population trends, obtained from the British Trust for Ornithology (BTO) “Bird
trends” online database ( http://www.bto.org/about-birds/birdtrends/2013 ), or the Joint
Nature Conservation Committee (JNCC) “Surveillance & Monitoring” online database
(http://jncc.defra.gov.uk/page-3356 ). Global conservation status information was obtained
from the International Union for the Conservation of nature (IUCN) “Red List” online
database (http://www.iucnredlist.org/search ).
Species photographs were all obtained from the Wikimedia Commons portfolio
(http://commons.wikimedia.org/wiki/Main_Page ).
Results
Distribution of counting effort
Visits were completed on 76 dates during the 6-month study period, representing 42% of
the 182-day period. Four of these dates included two independent counts by two different
members of the survey team. These “same-day repeat” counts were treated as independent
observations in the data analysis. Between 11 and 15 counts were completed per month
(median = 12.5 counts, Fig. 1), and the start-time of counts were distributed across the
daytime period (8am-4pm, median = 12:00 GMT, Fig. 2).
No. of counts
Figure 1. Distribution of counting effort by month
Oct
Nov
Dec
Jan
Feb
Mar
No. of counts
Figure 2. Distribution of counting effort by time of day
08
09
10
11
12
13
14
Start time of count (GMT)
15
16
Weather conditions
Weather conditions were noted on 68 of the 76 visit dates. Of these, 18 visits (26%) were
completed during rain, and 50 (74%) were completed in dry conditions.
Disturbance events
Dog walkers were observed within the boundary fence on four of the 76 count-dates (5% of
visits), and human disturbance (without dogs) was observed on a further four dates (5%).
Gunshots were heard from the fields north of the reservoir on 31st December 2013.
Species richness
The mean species richness (i.e. no. of species per visit) for the whole study period was;
10 species (median = 9 species, range 5-14 species). There was a small decline in the number
of species observed per visit, across the study period, from a mean of 11.2 species (range 813, median = 12 species) in October, to a mean of 8.6 species (range 5-11 in March, median
= 9 species. This decline was marginally statistically significant (GLM; Z = -1.979, d.f. = 1,74, p
= 0.0478).
Species accounts
Comprehensive accounts of “Regular” species (present on 10 or more visits) are presented
first, followed by brief accounts of “occasional” species (present on <10 visits).
[1] Mute Swan Cygnus olor
National Population Trend (BTO data)
Mean count = 0.3
Median count = 0
Maximum count = 2
Minimum count = 0
Peak abundance = Oct-Nov, March
UK population status: Green
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir:
Widespread, floating platforms
Comments:
A pair of mute swans often frequents Lisvane Reservoir, but were absent during the 2013-14
mid-winter period. Mute swans were recorded at Llanishen Reservoir and (in much larger
numbers) at Roath Park Lake during the period when they were absent from Lisvane
Reservoir, potentially involving the two Lisvane individuals.
[10] Canada Goose Branta canadensis
National Population Trend (BTO data)
Mean count = 14.5
Median count = 5.5
Maximum count = 138
Minimum count = 0
Peak abundance = October, December
UK population status: Introduced
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir:
Widespread, often grazing on the grass
banks
Comments:
The high count in October represents the tail end of the late-summer moulting flock, which
disperses in October-November. A subsequent peak in December was followed by a decline
over the remainder of the winter. Movement of Canada Geese was frequently observed
between Lisvane Reservoir, Llanishen Reservoir, and Roath Park Lake.
[24] Mallard Anas platyrhynchos
National Population Trend (BTO data)
Mean count = 8
Median count = 7
Maximum count = 27
Minimum count = 0
Peak abundance = December
UK population status: Amber (winter decline)
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir: Widespread,
including grass banks.
Comments:
Very variable in abundance, but a tendency towards higher counts in the first half of the
winter period. Regularly seen flying between Lisvane Reservoir and Llanishen Reservoir, and
to/from the direction of Roath Park Lake, where larger numbers of mallards are generally
present.
[32] Common Pochard Aythya ferina
National Population Trend – n.a.
No population trend available
Mean count = 13
Median count = 10
Maximum count = 39
Minimum count = 0
Peak abundance = Dec, Jan-Feb
UK population status: Amber
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir:
Widespread, particularly concentrated in the
northern and eastern sectors
Comments:
Generally less numerous than the tufted ducks with which it frequently associates. Two
distinct peaks in abundance occurred; earlier (Dec) and later (Feb) in the winter.
[36] Tufted Duck Aythya fuligula
National Population Trend (BTO data)
Mean count = 43
Median count = 40
Maximum count = 99
Minimum count = 9
Peak abundance = October, Dec-Jan
UK population status: Amber (declining)
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir:
Widespread, tending to avoid banks
Comments:
In 2013-14 there was evidence of substantial turnover of individuals over the winter, with
substantial fluctuations (+/- 50 birds) in the number of individuals present across the winter
period, and with birds regularly seen commuting between Lisvane and Llanishen Reservoirs,
and in the direction of Roath Park Lake.
[89] Cormorant Phalacrocorax carbo
National Population Trend (BTO WeBS data)
Mean count = 1
Median count = 0
Maximum count = 5
Minimum count = 0
Peak abundance = Oct-Nov
UK population status: Green (species level)
Amber (subspecies level)
Race carbo, >20% of European breeders
Race sinensis, localised breeding.
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir: Widespread,
including floating platforms, tending to avoid banks
Comments:
One or more cormorants (all assumed to be of race carbo) were frequently present, with a
tendency for lower numbers later in the winter.
[104] Grey Heron Ardea cinerea
National Population Trend (BTO Heronries Census)
Mean count = 0.3
Median count = 0
Maximum count = 2
Minimum count = 0
Peak abundance = Oct-Nov, February
UK population status: Green
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir: Sporadic, fishing
from the reservoir banks.
Comments:
One or more herons were often present, with presence less frequent in early October,
December, and March.
[112] Little Grebe Tachybaptus ruficollis
National Population Trend (BTO data)
Mean count = 9
Median count = 9
Maximum count = 17
Minimum count = 0
Peak abundance = November
UK population status: Amber
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir:
Widespread, often close to banks
Comments:
A clear decline in abundance across the winter period, from a peak in November to a
minimum in March.
[113] Great Crested Grebe Podiceps cristatus
National Population Trend (BTO data)
Mean count = 3
Median count = 2.5
Maximum count = 9
Minimum count = 0
Peak abundance = October, March
UK population status: Green
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir: Widespread
Comments:
A decline in abundance across the autumn, largely absent from the reservoir across the midwinter period (Dec-Jan), followed by an increase prior to the start of the breeding season.
[152] Eurasian Coot Fulica atra
National Population Trend (BTO data)
Mean count = 8
Median count = 8
Maximum count = 15
Minimum count = 0
Peak abundance = Nov-Dec, Feb-March
UK population status: Green
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir:
Widespread
Comments:
An unexpected pattern, of increase across the early winter, a sharp decline in mid-winter,
followed by an increase to the start of the breeding season.
[246] Black Headed Gull Croicocephalus ridibundus
National Population Trend
(JNCC data, coastal breeding population)
Mean count = 28
Median count = 19
Maximum count = 161
Minimum count = 0
Peak abundance = Oct-Jan
UK population status: Amber
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir:
Widespread, primarily northern half, with
the main Lesser Black-backed Gull roost.
Comments:
Highly variable in abundance over most of the winter period, with an overall decline from
December to February, and absent from early March.
[256] Lesser Black-Backed Gull Larus fuscus
National Population Trend
(JNCC data, coastal plus inland populations)
Mean count = 53
Median count = 47
Maximum count = 134
Minimum count = 6
Peak abundance = Oct, Nov-Dec, March
UK population status: Amber
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir:
Widespread, primarily in the northern half
Comments:
Numbers fluctuated widely over the winter, with peaks at the start and end of the recording
period, and in November-December.
[257] Herring Gull Larus argentatus
National Population Trend (JNCC data)
Mean count = 6
Median count = 5
Maximum count = 32
Minimum count = 0
Peak abundance = Oct, Nov-Dec, March
UK population status: Red
Global status (IUCN, Red list): Least concern
Distribution on Lisvane Reservoir:
Widespread, primarily northern half, with
the main Lesser Black-backed Gull roost.
Comments:
A similar pattern to Lesser Black-backed Gulls, with which the Herring Gulls associate,
though the Herring Gulls were always less abundant. Peaks occurred at the start and end of
the recording period, and in November-December.
Occasional species
[11] Barnacle Goose
One individual, on 27th December, may have been the same bird seen at several other sites
across Glamorgan over the winter period.
[22] Teal Anas crecca
Two birds were present on 16th November, and a single bird on 4th December. These may
have been part of the large flock of teal (20-40 individuals) over-wintering on the Llanishen
Reservoir pools throughout the survey period.
[29] Shoveler Anas clypeata
A single bird on 11th February.
[44] Common Scoter Melanitta nigra
A pair on 6th March.
[50] Goldeneye Bucephala clangula
A single bird on 15th December
[54] Goosander Mergus merganser
A single bird on 9th November
[221] Common Sandpiper Actitis hypoleucos
Single birds on two dates:
1 on 10th October and 1 on 10th November
[223] Green Sandpiper Tringa ochropus
Single birds on three dates: 1 on 26th October, 1 on 4th November, and 1 on 31st March
[254] Common Gull Larus canus
Small numbers present on eight dates: 4 on 14th October, 1 on 19th October, 3 on 1st
December, 3 on 10th December, 2 on 11th December, 1 on 13th December, 1 on 15th
December, 1 on 27th December.
[264] Great Black Backed Gull Larus marinus
A single bird on 14th October
[258] Yellow-legged Gull Larus michahellis
Single birds present on six dates: 1 on 28th November, 1 on 10th December, 1 on 31st
December, 1 on 22nd February, 1 on 1st March, 1 on 22nd March.
[323] Kingfisher Alcedo atthis
Single birds present on six dates: 1 on 9th November, 1 on 17th November, 1 on 6th
December, 1 on 24th December, 1 on 28th December, 1 on 3rd January.
Report compiled by Dr Rob Thomas, Cardiff University, July 2014.
Email: [email protected]