1 
220 
The Irish Naturalists 
September, 1906. 
ZOOLOGY. 
Pugnacity of the Common Tern. 
While shore-collecting on rocks to the north of Balbriggan, Co. 
Dublin, on the 20th July last, I was annoyed by the clamour of a pair of 
Common Terns {Sterna fluviatilis), which kept circling in the air a few 
feet above me. Their behaviour suggested the neighbourhood of a nest, 
and five minutes careful search was rewarded by the discovery of a 
young bird sitting motionless, yet keenly observant, at the upper angle 
of a large rock pool, near high-water mark. The still callow nestling 
sat partly in the water, and its coat of whitish, tawny down, mottled 
with gray, was extremely hard to separate from the surrounding lichen- 
clad rocks. The position of this nest, if nest it was, was peculiar, yet 
the bird was apparently too helpless to have scaled the deeply jagged 
and splintered rocks which hemmed in the pool, so that it was not im- 
probably hatched in the terraqueous cradle where I found it. While I 
stood inspecting the nestling at a distance of a couple of yards, from the 
opposite side of the pool, the conduct of the parent birds became most 
aggressive. They swooped down again and again to within a few inches 
of my head, and to save my eyes from the threatened attack I was 
obliged to clear a circle round me with a stick. After a short time I 
withdrew from the rocks, escorted, or rather chased, by the old birds, 
and sat down on the shore to watch their further movements. 
The rocks lay in the path of a procession of sea birds — Black-headed 
Gulls, Herring Gulls, and Lesser Black-backed Gulls— which kept 
passing northward in straggling lines to feeding grounds near the 
mouth of the Delvin river. Some of these gulls took a high-level route, 
thirty or forty feet above the rocks, others skimmed close over their 
jagged crests, but none of them appeared to pay the least attention to 
the rocks as they flew steadily northward. Nevertheless, the parent 
terns, who now kept hawking above the pool where their nestling lay, 
were full of distrust. They chased every gull that crossed the rocks by 
the low-level route, forcing the large birds to mend their pace, and, in 
some instances, striking the tail feathers of a laggard. The most 
amusing part of the performance was the perfect docility of the gulls. 
Not one of them made the least resistance to the apparently un- 
provoked attacks of the terns, who, no doubt, were secure in their 
superior agility against any onslaught of the more powerful birds. The 
gulls who took the high-level route were allowed to pass unmolested. 
In the Zoologist for June, Mr. W. H. Workman records an instance of a 
Blackbird rearing a brood of young, and then laying a second clutch of 
eggs in the same nest, near Belfast. 
N. COI^GAN. 
Sandj'cove. 
Blackbird laying twice in same nest. 
