dave.grant@uws.ac.uk
This report on the 2013-2014 Lady Isle gull colour ringing project first appeared in the Ayrshire Bird Report 2014 and is published with permission from Ayrshire SOC.
Preamble
Lady Isle is a small island situated 5.6 km off the coast of Troon (OS Grid Ref. NS 276 292) in Ayrshire, with a high point of only 6 metres above sea level and an area of approximately 4.4 hectares. It has a rocky shoreline, which often makes landing difficult at certain states of the tide.
Whilst Lady Isle may be best known ornithologically for its historic and, now extinct, colony of Roseate Tern Sterna dougalli (Gibson 1969), it is currently of importance as a gull roost and breeding site for Herring Gull Larus argentatus, Lesser Black-backed Gull Larus fuscus and Great Black-backed Gulls Larus marinus as well as Cormorant Phalacrocorax carbo, Shag Phalacrocorax aristotelis and Common Eider Somateria mollissima. Whilst there are records of a few pairs of Lesser Black-backed and Herring Gulls breeding on Lady Isle in the 1940s, this population remained small until the 1970s (Gibson 1985). Gibson suggests that the relatively low numbers of larger gulls on Lady Isle may have been due to the effort to protect the Roseate Tern colony by controlling the numbers of large gulls and that these measures were carried out unceasingly until the early 1970s. However, with the reduction in numbers of terns over all the Clyde area, the Roseate Tern soon disappeared as a Clyde breeding species. Shortly after this period, the control of large gulls ceased and within a few years the large gull population increased enormously. This was reflected within the wider Clyde area, as the combined breeding population of larger gulls grew from just under 250 pairs at the end of the nineteenth century to over 12,500 pairs by 1985 (Gibson 1985). A comprehensive survey of the breeding gull population on Lady Isle in 2012 (Grant et al. 2012) suggested that the Herring Gull population on Lady Isle may represent as much as 4-5% of the total Scottish breeding population.
The Research
Lady Isle had been the focal point for an ongoing research project into antimicrobial resistance in seabirds. This has necessitated the need for capturing gulls and taking cloacal swabs from them for lab analysis. As part of the capture process the gulls had colour rings, each with a unique alpha-numeric code, placed upon their left tarsus. On their right tarsus (to balance the bird 😊) was placed a metal BTO ring, also with a unique code. Additional biometric data was taken from each bird for later analysis using eye-widening statistical techniques such as binomial general linear modelling (a form of academic self-harming). Capture of the birds depended upon whether adults or chicks were required. As the capture of an adult gull took approximately seven man hours (involving patience, observation, more patience and a lot of luck) due to their propensity to take flight when a fieldworker got close, compared to chick capture, which involved picking up unfledged birds invariably from underneath a stinging nettle, at a rate of six birds per hour, as such it may not come as much of a surprise (especially to those time and motion managers amongst you) that the main focus was upon chicks rather than adults.
Citizen Science in Action
The colour rings were orange in colour with black writing which made them very visible and easy to read by anyone with binoculars or with some excess fish and chips that they wanted to share with the gulls. Observers of these colour ringed gulls would not only take note of the code but would quite often use their digital image capture device (a mobile phone 😊) to record the ring code. From a researcher’s point of view this has been very useful as it serves to act as a confirmation of the bird identity, thereby reducing potential observer bias (very important). Once someone had recorded their observation their next step would be to send their report in to the co-ordinator for that specific colour ring scheme. This is a lot easier than it sounds as there is a website called European Colour-Ring Birding that is found at: www.cr-birding.org. Below are instructions specifically for the colour ring scheme used on Lady Isle gulls:
- Once on the web page the observer clicks on the tab ‘Info Field-Observer’, which will produce a drop-down menu.
- Click on ‘Find a Colour-Ring Project’.
- There are a series of data fields that need to be completed but should not be too daunting.
- Under ‘English species name’ insert either Herring Gull or Lesser Black-backed Gull.
- Under ‘Colour-ring type’ click on ‘Legring: one, coded’.
- Under ‘Colour-ring colour’ click on ‘Orange’.
- Under ‘Colour-ring code’ click on ‘Four alpha-numeric code (4 letters/number)’.
- Click ‘Apply’.
- This will show you a list of potential schemes, and this is where you need the code of the bird that you have seen for example the Lady Isle gulls have a code which is “alpha:alpha numeric” e.g. A:B75.
- By looking down the right-hand columns the observer should be able to find either the first letter or last letter. In the case of Lady Isle Herring/Lesser Black-backed Gulls the first letter is an ‘A’, so on the left-hand side of the table is a link which if clicked takes you to information on the co-ordinator, which includes an email address. For Lady Isle this is: grant@uws.ac.uk.
- Most colour ring scheme co-ordinators will reply to an email of a report of one of their birds within a week or so, quite often with a history of that bird.
- An alternative route is to contact the BTO but this can be a time-consuming process and you may not get any feedback for quite a few weeks.
Colour ring birding is not yet an Olympic approved sport but there are more and more individuals who are going out birding with the specific aim of looking for colour ringed birds. This is great news for those who run colour ring schemes and is an important part of the data capture process.
Results for 2013 & 2014 Seasons
During the 2013 and 2014 breeding seasons 322 Herring Gull and Lesser Black-backed Gulls were colour ringed on Lady Isle. The majority of these were chicks (90%). Table 1 shows that whilst adult birds are harder to capture, they do provide a better return on the percentage of individuals reported, with both Herring Gull and Lesser Black-backed Gulls showing more than 60% of individuals being seen after they had been colour ringed. In comparison chicks, from both species, yielded a reporting rate of only 22% of individuals being seen after they have been colour ringed. There are a greater number of reports of chicks but this is due to the greater number being ringed in the first place.
| 2013 | 2014 | 2013-14 Cumulative | ||||
| Species (age) | No. of colour rings reported (Total colour ringed) | No. of individuals reported (% of sightings) |
No. of colour rings reported (Total colour ringed) | No. of individuals reported (% of sightings) |
No. of reports of colour rings (Total colour ringed) | No. of individuals reported (% of sightings) |
| HERGU (adult) | 0 (2) | 0 (0) | 24 (15) | 13 (87%) | 24 (17) | 13 (76%) |
| HERGU (chick) | 35 (76) | 24 (32%) | 34 (78) | 17 (22%) | 69 (154) | 34 (22%) |
| LBBGU (adult) | 1 (9) | 1 (11%) | 16 (7) | 5 (71%) | 13 (16) | 10 (63%) |
| LBBGU (chick) | 16 (69) | 12 (17%) | 52 (66) | 19 (29%) | 72 (135) | 30 (22%) |
Note: HERGU – Herring Gull; LBBGU – Lesser Black-backed Gull
Most observations of birds came after the chicks had fledged. During the 2013 season (from end of July to end of December) 18 observers sent in a total of 52 reports of colour ringed birds (2.9 sightings per observer). The number of observers sending in reports of colour ringed birds increased to 47 during the 2014 season, with 126 sightings being made (2.7 sightings per observer). The cumulative totals for both seasons are 60 observers sending in 178 observations (2.97 sightings per observer). During this period, the mean number of observations per observer was 3, however the range was 1 to 60 with a standard deviation of 8, so clearly the data were skewed and someone was spending more time out looking for gulls when they should have been at their work desk!
Where were the birds seen?
As would be expected there was a clear difference between where Herring Gulls were seen during the non-breeding season compared to the Lesser Black-backed Gulls. Herring Gull are partial migrants and whilst some do wander a distance most tend to stay within a 40km or so of their natal home (see Table 2). There were, however, several reports of Lady Isle colour ringed Herring Gulls seen on Isle of Man, Merseyside and a couple of winter staying birds in southern Eire, in Bray Harbour, Co. Wicklow.
| Species | Mean distance (km) reported from Lady Isle (Stdev) | Furthest Distance (km) | Note on furthest distance |
| Herring Gull | 33 (86) | 403.5 | Dunmore Harbour, Waterford, Eire |
| Lesser Black-backed Gull | 1327 (750) | 2118 | Cruz del Mar Beach, Chipiona, Cádiz, Portugal |
By comparison Lesser Black-backed Gulls are a migrant species and obviously the cleverer of the two species as they head south to the warmth of the Mediterranean during the non-breeding season whereas the Herring Gull opt to stay in slightly cooler and damper environs of the south-west of Scotland. Forty-five reports of Lesser Black-backed Gulls came from Portugal, whilst there were nine reports from Spain. There were some reports of birds seen on route to the Mediterranean in Merseyside and Cornwall. Whilst most of the birds were observed in coastal areas there were two reports of winter staying birds in the centre of Spain in Madrid.
Epilogue
The project is ongoing and is to date yielding some interesting information on the movement patterns of our gulls. In future editions of the Bird Report updates on the project will hopefully be provided. However, without the support of birders reporting their sightings of colour ringed gulls, projects such as this would not be as effective. So, if you fancy getting involved head down to the coast (with binoculars, bread or extra chips) and look for those colour ringed gulls and send in your sightings to the appropriate co-ordinator, who I know will be very appreciative of your support. Good luck and see if you can beat the current record of 60 sightings, though no responsibility is accepted for the effect it may have on work or home life!
Acknowledgements
A big thanks to all those birders who have and continue to send in their reports of colour ringed gulls.
References
Gibson, J.A. 1969 Populations Studies of Clyde Seabirds: Part 1, Transactions of the Buteshire Natural History Society, 17: 79-95
Gibson, J.A. 1985 Populations Studies of Clyde Seabirds: Part 4, Transactions of the Buteshire Natural History Society, 22: 85-105
Grant, D., Robertson, D., Nager, R. & McCracken, D. (2013) The status of breeding gulls on Lady Isle, 2012, Scottish Birds, 33(4):298-307