Horse Island Breeding Bird Report 2003
Marco McGintyLochwinnoch RSPB Nature Reserve
Largs Road, Lochwinnoch, Renfrewshire, PA12 4JF
Tel: (01505) 842663
Fax: (01505) 843026
E-mail: Lochwinnoch@rspb.org.uk
See also: Horse Island Breeding Bird Report 2002.
Summary
The main visit to Horse Island RSPB Nature Reserve to census the breeding birds was made on 14 May 2003. In addition to this visit, two further visits were made by the Clyde Ringing Group on 28 May and 14 June 2003. A table summarising the total number of nests/pairs counted and thought to be breeding is presented below. Twelve species were confirmed breeding this year, another three were probably breeding (shag, shelduck and rock pipit). Snipe may have been breeding with birds flushed from suitable habitat on two transects.
| Species | No. of Nests/Pairs |
|---|---|
| Cormorant | 87 |
| Mute Swan | 3 |
| Greylag goose | 1 |
| Teal | 1 |
| Mallard | 2 |
| Eider | 484 |
| Moorhen | 4 |
| Oystercatcher | 7 |
| Great black-backed gull | 46 |
| Lesser black-backed/Herring gull | 2101 |
| Common gull | 8 |
| Total Number of Nests/Pairs | 2744 |
Timing and Conditions
On 14th May, due to poor weather in the morning, the survey did not commence until approximately 1345 hours, ending at 1850 hours. The weather, whilst we were on the island, was favourable with warm with sunny spells and a gentle breeze.
Fieldworkers
14 May: Tony Barr, Zul Bhatia, Frank Gibbons, Jim Kennedy, Scott Maxwell, Marco McGinty, James Towill, Jen Walker and Chris Waltho. 28 May: Iain Livingstone (Clyde Ringing Group) and Chris Waltho (SOC/Clyde Ringing Group). 14 June: Iain Livingstone, Charlie Howe and Dr N Darroch (all Clyde Ringing Group).
Survey Methodology, 14 May
The main part of the island was surveyed in nine parallel-sided sections (transects) with the fieldworkers walking side by side and at the same pace on a broad front, recording all nests found. The East Islet was counted in two transects and the North Islet in one. The edges of these transects were marked with a line of bamboo canes with conspicuous flags on top. The fieldworkers thoroughly covered the whole island by walking approximately 4 to 5 metres apart and counted nests on either side of them. Adjacent observers kept each other briefed on what had already been counted thus avoiding double counting. Surveying of the main island commenced at the southerly end surrounding the beacon tower and finished at the northern section of the island. The islets were then surveyed after this point.
Breeding Data - Systematic List
Cormorant Phalacrocorax carbo
The colony first established in 1996 had remained relatively constant in size for the previous three years, but this year saw a slight increase to 87 nests. The census visit of 14th May recorded 23 nests on the main island with a further 64 on the East Islet (49 at the main colony and 15 at the smaller satellite colony). The visit on 14th June enabled the Clyde Ringing Group to capture and ring 70 cormorant chicks.
| Year | No. of Occupied Nests |
|---|---|
| 1996 | 1 |
| 1997 | 16 |
| 1998 | 39 |
| 1999 | 51 |
| 2000 | 76 |
| 2001 | 72 |
| 2002 | 73 |
| 2003 | 87 |
Mute Swan Cygnus olor
Three pairs bred on the island, one pair having a nest with a clutch of five eggs, one with one egg and the other having a clutch of six eggs. The pair with the clutch of five eggs were both colour-ringed - Orange 3AUX and Orange 3AUV. These birds had been ringed at Saltcoats Boating Pond on 5 February 2002, bred on the island in 2002 (with a clutch of two) and were seen back at Saltcoats Boating Pond on 19th November 2002. The pair with one egg were both unringed birds and of the pair with six eggs, the incubating bird had the metal ring X4826. This bird had been seen previously at Auchenharvie Golf Course Pond, Stevenston on 4 November and 10 November 2001, with a follow-up sighting at Irvine Harbour on 4th February 2002. Its partner also bore a metal ring but this could not be read in the field as it quickly fled on our approach. This pair had also bred on Horse Island the previous year when they had four eggs.
Greylag Goose Anser anser
Four adults were seen and one gosling was noted. A greylag goose egg was noted together with a clutch of five eider eggs in the same nest.
Teal Anas crecca
One nest was found, containing a clutch of seven eggs.
Mallard Anas platyrhynchos
As with the previous year, two nests were located, one containing a clutch of three eggs, the other containing a clutch of seven eggs.
Eider Somateria mollissima
Numbers of nests were down this year, with 484 nests counted, compared to 548 in 2002. Disturbance was kept to a minimum, but where birds did fly off the nest, the clutch size was recorded. Although nest numbers were lower than the previous year, the data gathered from the clutches produced a mean clutch size of 4.10, the highest ever recorded at the s ite (c.f. 4.07 in 2002). Empty nests refer to birds that had already hatched young or were yet to lay eggs. Clutch data is presented in the table below:
| Clutch Size | No. Clutches/Nests | Total No. of Eggs |
|---|---|---|
| 1 | 11 | 11 |
| 2 | 18 | 36 |
| 3 | 64 | 192 |
| 4 | 84 | 340 |
| 5 | 113 | 565 |
| 6 | 13 | 78 |
| 7 | 4 | 28 |
| 8 | 3 | 24 |
| Birds incubating | 159 | N/A |
| Empty nests | 4 | N/A |
| Eider/Goose combination | 1 | Data unavailable |
| Eider/Gull combination | 8 | Data unavailable |
| Broods of ducklings | 1 | Data unavailable |
| Total | 484 | 1286+ |
Of the 484 nests, 56 nests were on the East Islet, three on the North Islet and the remainder on the Main Island. Of the dedicated ringing visits, the 28th May visit had been severely delayed due to poor weather the previous week and due to this problem, many eiders had hatched their eggs and had left the island. Despite this, 27 adults were caught and ringed and ten birds that were previously ringed on the island (2 in 2001, 8 in 2002) were re-trapped. On the final visit, another two adult eiders were ringed.
Moorhen Gallinula chloropus
The island held at least four pairs this year. Two birds incubating, one bird flushed from a probable nest site and an adult with a chick were all noted during the survey. Two predated eggs were also discovered, but these could have been the result of a previous nesting attempt.
Oystercatcher Haematopus ostralegus
An estimated seven pairs used the island this year with five nests located and two territorial pairs. Of the nests found, two had clutches of three, two had clutches of two and one contained one egg.
Common gull Larus marinus
Eight nests were found during the course of the survey. This is in stark contrast to last year's survey, when no nests were located.
Great black-backed gull Larus marinus
On this occasion, 46 nests were to be found, in comparison to the poorly recorded session of 2002 when only eleven were found. Members of the Clyde Ringing Group, were able to ring 29 birds on 14th June.
Lesser black-backed gull/Herring gull Larus fuscus/L argentatus
A slight increase this year with 2101 nests counted, compared with 1866 in 2002. The Clyde Ringing Group visit in June, managed to ring 124 chicks of the two species (117 lesser black-backed gulls, 7 herring gulls).
Miscellaneous Bird Observations
The journeys to and from the island produced several sightings of shags, gannets, black-headed gulls, sandwich terns and black guillemots as well as the breeding species documented above. From the island, other probable breeding species on the island were shag (two possible pairs in amongst the cormorant colony, shelduck (two pairs of adults just offshore), snipe (a possible breeder) were flushed from suitable sites on the island and rock pipit (one alarm-calling bird).
Non-avian inhabitants included green-veined white and small tortoiseshell butterflies and many caterpillars of the garden tiger moth.
During the first visit of the Clyde Ringing Group, on 28th May, 7 dunlin, 7 turnstones and 2 whimbrel were noted and on their second visit (14th June) a painted lady butterfly was observed, a common migrant in some years.
Ringing Data
Iain Livingstone of the Clyde Ringing Group has kindly provided us with ringing data concerning species which had been ringed on Horse Island.
| Species | Ringing Date | Recovery Location | Recovery Date | Duration/ Distance | Comments |
|---|---|---|---|---|---|
| Cormorant | 3 July 2002 | Ythan Estuary, Grampian | 15 Feb 2003 | 227 days/256 km | Found dead |
| Lesser black-backed gull | 24 June 2001 | West Kilbride, Ayrshire | 11 Feb 2003 | 597 days/6 km | Found dead |
| Lesser black-backed gull | 3 July 2002 | Ardrossan, Ayrshire | 1 Oct 2002 | 90 days/2 km | Found dead |
Acknowledgements
Our thanks are due to all the fieldworkers, Saltcoats Police, Clyde Coastguards, Clydeport Authority and the boat operators David Hodge and Suzanne Mackay for their help during our visits to the island in 2003.