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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) peaked in late-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, with maximum and minimum and average (mean and median) winter abundance of each, is given in the main text. 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, 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 3060 mins., and as well as the numbers of each waterbird species, 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]