Geoff continues to check the monitoring grid. Since the last report there has been one further complete check, round 6. On this round 675 stations were checked, some (Nunnery, Lamasgor and Geugasgor) by Bob Swann. 292 stations (43%) had mice nibbles. As the summer has progressed the mice have had plenty of natural food resources to exploit, so the percentage of blocks nibbled has continued to decline. No rat signs were detected.
On 26th July we had a reported rat sighting at the Celtic Cross, by a visitor to the island. Geoff, implemented the contingency plan by setting up a bait station grid round the site of the report, with bait blocks every 50m, some in stations, others outside. These were checked for two weeks, but no rat signs were detected. One block was, however, nibbled by a mouse.
Seabird monitoring work has also been ongoing. Following the dreadful 2005 breeding season on Canna birds fared much better in 2006, with most showing higher levels of breeding output. This was situation, for many species was, however reversed in 2007.
| |
2004
|
2005
|
2006
|
2007
|
|
Fulmar
|
0.6
|
0.3
|
0.5
|
0.3
|
|
Shag
|
1.2
|
0.7
|
1.2
|
1.2
|
|
Great B-B Gull
|
0.3
|
0.1
|
0.2
|
0.8
|
|
Herring Gull
|
0.2
|
0.1
|
0.2
|
1.8
|
|
Kittiwake
|
0.8
|
0
|
0.5
|
0.3
|
Highland RG data gathered under contract to JNCC
The table above shows the average number of young per monitored pair. Shag breeding success remains above the very low level seen in 2005. Birds in boulder colonies did well, possibly as a result of reduced rates of predation. Fulmar and kittiwake, both showed low levels of success, with many failures at the small chick stage. These appeared to be related to food shortages. Many kittiwakes were trying to feed snake pipefish to their chicks. The chicks found these unpalatable and tended to discard them, and as a result of this many died from starvation.
Although we do not formerly assess breeding output of common guillemots and razorbills, it was obvious that both species were suffering from food shortages. Very few fish were recorded being brought into the colonies to feed chicks. Only 1 sprat was recorded. Formerly these high calorific fish, rich in oils, accounted for around 60% of the diet of young guillemots on Canna. A number of large chicks were weighed just prior to fledging. Their mean weight of 239g was 30g below the mean weight recorded prior to 2005. Although we do not weigh Razorbill chicks, it was obvious that many were very underweight. They looked very anorexic, with almost skeletal legs and were continually calling out for food.
Gulls, however, had their best breeding season since 2000. The Herring Gull population is, possibly, now back in sync with the much reduced food supply, and also benefiting from the rat eradication programme.
Lots of bookings are coming in for the EU Life (Nature) Fund post project conference, being jointly hosted by The National Trust for Scotland, Royal Zoological Society of Edinburgh and Central Science Laboratory and entitled:Tackling the Problem of invasive alien mammals on seabird colonies - Strategic approaches and practical experience. It is being held on 18-19 September 2007, at the Education Centre, Edinburgh Zoo. A booking form, giving full details of the finalised programme can be found on the project website by clicking on:
http://www.nts-seabirds.org.uk/File/CSRP%20booking%20form1(3).doc
Remember bookings received after 18th August 2007, will incur a late booking fee, so if you have not booked yet, get your form in as soon as possible.
Bob Swann
Project Administrator
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