Figure 1 Allopreening
It is when the pairs are re-establishing their sites that the most aggression occurs. If the bird feels threatened, for example, if another bird is intruding of its territory, then it will assume the alert-posture (figure 2), whereby it stands upright, extends its neck and raises its wings. Often alert-bowing will follow, where the neck moves rapidly down in an arc and then up again. The rival will respond by assuming the alert-posture as well and rebuffing the attack by pointing and stabbing its beak at its opponent. If the aggression escalates then the birds stand on their tip-toes and lift their wings higher, they can then start jabbing and grappling their beaks. However full blown fights like this weren’t common and aggression was more regularly meet with appeasement behaviour. This behaviour is well-develop to aid high-density nesting and most antagonistic interactions compromise one bird threatening and the other would display an appeasement behaviour after first retaliating briefly. Appeasement behaviours include side-preening (figure 3), turning-away and stretching-away (figure 4).
Figure 2 Alert-posture
Figure 3 Side-preening
Figure 4 Turning-away (left) and stretching-away (right)
Guillemots do not build a nest; the egg is laid directly onto the ledge. An interesting adaption to what might seem a perilous situation is it that the eggs are heavily taped at one end (figure 5); this means an egg will roll in tight circles rather than off the edge of the ledge. Both parents take it in turns to incubate the egg for up to 24 hours at a time. The egg rest on the bird’s feet and is then tucked tightly under the bird as they sit on it, there it rests against a brood-patch. This is an area of skin without feathers and is well-supplied with blood-vessels at the surface; it is an adaption many birds have to increase heat transfer to their egg(s). This also means the egg is completely out of sight to predators, such as the herring gulls. The off-duty mate roosts at sea along with immature birds, leaving just the incubating birds on the cliffs at night. In the morning and evening the number of birds on the cliffs increases as the birds change-over. The change-over is a ritualised and careful manoeuvre; the off-duty bird first approaches the incubating bird and bows its head. Sometimes the incubating bird appeared to ignore this action so its mate would preen it until it agreed to move. This agreement was demonstrated by mutual head-bowing and then both birds would shield the egg by raising their wings as the change-over happened. This would happen quickly and the raising of wings is clearly an anti-predator adaption as this is when the egg is most exposed.
Later in the season younger non-breeding birds also increasing begin to visit the breeding ledges. This combined with birds that had failed and wandering chicks, not forgetting preying gulls, made for a hectic colony. Then as soon as they arrived they began to leave.
The chicks start to ‘jump’ at around two weeks old. They are called jumplings rather than fledglings as they leave the nest before they can fly, and jump into the sea. This happens on calm evening before dusk and with a colony here of over 30,000 birds they jump in quite quick succession. I would certainly recommend having a picnic on the top of the cliffs around the summer solstice to witness this amazing spectacle. Chicks are seen wandering around, preening frantically and flapping their tiny underdeveloped wings. They then move to the edge of the cliff with their father, bowing to each other as they go and being pecked by the other birds they have to squeeze past. Once at the edge they bow more and more frequently until the chick jumps! They normally fall straight down with their wings and large feet outspread and will land on their bellies. If they’re lucky they will hit the water but many bounce of rocks as the fall and may have to jump a few more times before the reaching the sea. There they are reunited with their father and swim out to sea, he will care for the chicks for up to another 12 weeks. The mother stays at the nest site for up to three weeks after the chick has fledged.
And that is the amazing breeding season of a Guillemot, there’s certainly a lot to it and I feel very lucky to seen all those varied and wonderful moments. After completing my work in the morning to monitor the breeding success of the guillemots and the razorbills and I was able to ‘pop-up’ and talk to some of you up on the cliffs. As I sure many of you know we had a pair of Kestrels nesting on the cliffs this year, very well camouflaged but in plain view and close enough to be able to observe them with ease. This was one of the things I most enjoyed sharing with visitors. As they were so well camouflaged most people were unaware of their presence but once pointed out they couldn’t believe how close they were. I know it was for me, and I think it was for many others, the best view of kestrels they have ever had. We had four young kestrels fledge from that nest and we see them soaring overhead on the reserve regularly. What a spring!
Written by Charlotte (assistant ranger)
Written by Charlotte (assistant ranger)