The 2005 breeding season turned out to be the worst experienced in the 37 year period since regular monitoring first started on Canna in 1969. For several species total island counts revealed that numbers had dropped to an all time low. For most species breeding success was below or well below average.

Canna formerly held one of the largest shag colonies in Europe. Numbers have been declining over the last few years and in 2005 reached a record low of only 327 occupied nests. The big boulder colonies on the western half of the island are now totally deserted.  By the time of our visit in early July, many nests were empty having had their eggs predated by a combination of rats, gulls and ravens. Because many shags now nest out in the open to try and avoid rat predation, they are more susceptible to predation by other birds. In all only 0.7 chicks were fledged per nest, about half of what we would normally expect.

Gulls also continued their recent dramatic declines. Herring Gulls reached a record low of only 112 apparently occupied territories (AOTs), down from a peak of 1525 AOTs in 1988. Only 4 pairs of Lesser Black-backed Gulls were found, down from 40 pairs in 2002. Similarly Great Black-backed Gulls have dropped from 93 AOTs in 1997 to 29 AOTs in 2005. Only Common Gulls showed a slight increase from 6 pairs in 2005 to 9 pairs in 2005. Gull breeding success was also very poor. We estimated that just 15 Herring Gull chicks fledged from the entire island (0.13 per AOT) and of the 23 Great Black-backed Gull pairs that were monitored, 20 failed and three produced single chicks (0.13 per pair).

Following years of increase to a peak of 1340 occupied nests in 2004, Kittiwake numbers dropped to only 968 occupied nests in 2005. Many birds did not bother to build nests, whilst many of those that did failed to lay eggs. There then followed an almost complete breeding failure. No birds in our five study plots raised any young, indeed it was estimated only 5 chicks were fledged from the entire island. This is the worst breeding season recorded for this species on Canna.

For the first time since monitoring work began, Guillemots had a dreadful breeding season. Many of the colonies had been abandoned by the time we visited the island in early July. The chicks that had survived were small and underweight. We observed very few fish being brought in by breeding adults. Similarly most Razorbills had already failed and had abandoned their nesting sites. The few surviving chicks were starving and continually calling for food. Large chicks were extremely underweight, more reminiscent of a powder puff than a plump auk chick.

There were few successes to report. Although fulmar numbers remained stable at just over 400 apparently occupied sites (AOSs), breeding success at 0.28 chicks per AOS was well below the ten year average of 0.39 per AOS. Two pairs of Great Skua bred and one fledged a single chick. Three pairs of Common Tern also nested and although two of the pairs failed, the third, against all the odds, fledged all three of its chicks.

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